Seafood Watch
Seafood Report
Atlantic Mackerel
Scomber scombrus
©Scandinavian Fishing Yearbook
Atlantic Canada
March 17, 2011
Damian C. Lidgard
Independent consultant
Dalhousie University, Halifax NS
Atlantic Candian mackerel
March 17, 2011
About SeaChoice, Seafood Watch® and the Seafood Reports
This report is a joint product of SeaChoice and the Monterey Bay Aquarium Seafood Watch®
program. Both organizations evaluate the ecological sustainability of wild-caught and farmed seafood
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the long-term without jeopardizing the structure or function of affected ecosystems.
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2
Atlantic Candian mackerel
March 17, 2011
Table of Contents I. Executive Summary ........................................................................................................................... 4 II. Introduction ........................................................................................................................................ 7 III. Analysis of Seafood Watch® Sustainability Criteria for Wild‐caught Species .... 16 Criterion 1: Inherent Vulnerability to Fishing Pressure .................................................................. 16 Criterion 2: Status of Wild Stocks .............................................................................................................. 20 Criterion 3: Nature and Extent of Bycatch ............................................................................................. 26 Criterion 4: Effect of Fishing Practices on Habitats and Ecosystems .......................................... 29 Criterion 5: Effectiveness of the Management Regime ..................................................................... 31 IV. Overall Evaluation and Seafood Recommendation ....................................................... 37 V. References ........................................................................................................................................ 40 3
Atlantic Candian mackerel
I.
March 17, 2011
Executive Summary
The Atlantic mackerel (Scomber scombrus) belongs to the family Scombridae, which
consists of 51 species including the tunas and bonitos. As the name implies, Atlantic
mackerel are found throughout the north Atlantic ocean. In the northwest Atlantic,
Atlantic mackerel range from North Carolina to Newfoundland, Labrador and the Gulf of
St. Lawrence. Mackerel are migratory: they move offshore during the winter months and
return to coastal waters in spring to spawn at their traditional spawning grounds in the
southern Gulf of St. Lawrence and more recently along the west coast of Newfoundland.
Atlantic mackerel exhibit biological characteristics that suggest low vulnerability to
fishing predation. They are a fast-growing species reaching both the current legal catch
size of 250 mm and sexual maturity at a young age. They have a moderate lifespan and
high fecundity. As noted above, the distribution of Atlantic mackerel is wide and the
quality of their habitat is moderate; certain environmental changes, such as reduced
predation pressure from groundfish, benefit the population while others likely cause
detriment, e.g., coastal development. These factors make Atlantic mackerel a highly
resilient species.
The population structure of mackerel is characterised by periodic large year-classes,
which may dominate the fishery for several years. Since the early 1960s, Canadian
vessels have caught Atlantic mackerel in the present day fishing areas of the east and
south coasts of Newfoundland (NAFO subarea 3) along with the Gulf of St. Lawrence
and the Scotian Shelf (NAFO subarea 4). Canadian catches of Atlantic mackerel
increased during the period from the 1960s to the 1980s due to several strong yearclasses. Catches then declined during the 1990s and were high during the early and mid2000s due to the strong 1999 year-class. Since the early 2000s, the majority of catch
comes from the coasts of Newfoundland, likely due to changes in water temperature in
the Gulf of St. Lawrence and along the Scotian Shelf. The status of the Atlantic mackerel
stock is a moderate conservation as many factors remain unknown due to high
uncertainty in the most recent stock assessment.
Purse seining is the dominant method of fishing Atlantic mackerel in Canadian waters.
Due to the absence of an observer program, no data are available on the quantity or
composition of bycatch. Consequently, bycatch is a moderate conservation concern even
though purse seines are known to have low bycatch rates.
The purse seine has minimal impact on the seafloor habitat because there is no physical
contact with the seafloor. Atlantic mackerel is an important forage species for several
species of marine mammal, although the current highest mortality comes from fishing.
Marine mammals are able to adapt to changes in prey availability, though they may be
negatively affected if multiple forage stocks decline. Overall, impacts on habitats and
ecosystems are a low conservation concern.
Stock assessments of Atlantic mackerel have been conducted in the Gulf of St. Lawrence
on a regular basis since the 1960s. Data from these assessments are used to calculate the
spawning stock biomass along with an index of population abundance for Canadian
4
Atlantic Candian mackerel
March 17, 2011
waters. The spawning stock has been monitored since 1915. Scientific advice has been
given on the above issues along with others such as monitoring recreational activities,
extending the current range of the egg survey and lowering the total allowable catch
(TAC). Some of these changes are under discussion while others have already been
implemented. Management plans are in place to control bycatch, varying by province.
As mentioned above, the fishing gear used in Canadian waters is mostly purse seines,
which have minimal impact on the environment and thus eliminate the need for
management efforts to reduce habitat impacts. Catch monitoring of commercial fishing
needs to be improved; there is no monitoring of bait or recreational fishing. Nevertheless,
the DFO has enforcement strategies in place for fishery violations. Atlantic mackerel
have not been overexploited since the 1970s when foreign fleets were prominent.
Concern over inaccuracy of the SSB and a lack of bait and recreational fishing
monitoring led to a lowered TAC. New authorizations on mackerel gear have also been
frozen. As a result of regular monitoring, effective enforcement, bycatch prevention, and
compliance with scientific advice regarding quotas, management of the Atlantic mackerel
fishery in Canada is considered highly effective.
Overall, due to its low inherent vulnerability, benign impact on the habitat and
ecosystem, and highly effective management, the Atlantic mackerel fishery is a Best
Choice.
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Atlantic Candian mackerel
March 17, 2011
Table of Sustainability Ranks
Sustainability Criteria
Inherent Vulnerability
Conservation Concern
Moderate
High
Low
√
√
√
Status of Stocks
Nature of Bycatch
Habitat & Ecosystem
Effects
Management Effectiveness
Critical
√
√
About the Overall Seafood Recommendation:
• A seafood product is ranked Best Choice if three or more criteria are of Low
Conservation Concern (green) and the remaining criteria are not of High or
Critical Conservation Concern.
• A seafood product is ranked Good Alternative if the five criteria “average” to
yellow (Moderate Conservation Concern) OR if the “Status of Stocks” and
“Management Effectiveness” criteria are both of Moderate Conservation
Concern.
• A seafood product is ranked Avoid if two or more criteria are of High
Conservation Concern (red) OR if one or more criteria are of Critical
Conservation Concern (black) in the table above.
Overall Seafood Recommendation:
Best Choice
Good Alternative
6
Avoid
Atlantic Candian mackerel
II.
March 17, 2011
Introduction
Biology
The Atlantic mackerel (Scomber scombrus) belongs to the family Scombridae, which
consists of 51 species (Collette and Nauen 1983) including the tunas and bonitos. They
are distributed throughout the tropical, subtropical and temperate seas and are
characterised as being fast, epipelagic and predatory. The Atlantic mackerel is the only
species of the genus Scomber characterised by the absence of a swim bladder. The
Atlantic mackerel is also characterised by a spiny dorsal and a soft dorsal fin along with
finlets behind the latter and the anal fin. The caudal peduncle is slender, the caudal fin
short but deeply forked, and the whole body tapers at each end resembling a torpedo
(Bigelow and Schroeder 1953). The scales are very small giving the fish a velvety feel.
The upper body is dark grey to greenish-blue with 23 to 33 dark transverse irregular
bands that extend to the midline. The ventral surface is white.
Atlantic mackerel are found in the northwest Atlantic (and northeast) from as far south as
North Carolina and as far north as Newfoundland and Labrador and the Gulf of St.
Lawrence (DFO 2007) (Fig. 1).
Labrador
CANADA
Newfoundland
Québec
New
Brunswick
New
Ham
psh
ire
v
No
ia n
Grand Banks of
Newfoundland
She
lf
200 m
Georges
Bank
Subarea 3
200 nautical miles
limit
Rhode Island
Ne w
Jersey
USA
ia
co t
aS
t
Sc o
Massachusetts
Connecticut
0m
PEI
Maine
New York
20
Subarea 4
Delaware
Maryland
Virginia
North Carolina
Cape Hatteras
20
0m
Figure 1. Distribution of Atlantic mackerel in the northwest Atlantic. The NAFO subareas 3 and 4 are
shown (modified from (Grégoire et al. 2007)).
7
Atlantic Candian mackerel
March 17, 2011
A northern and southern group of Atlantic mackerel have been identified that follow
different migration routes and spawn in different areas (Sette 1950). During the winter
months, the two groups congregate in the deep waters of the continental shelf extending
from Sable Island Bank, Nova Scotia to the Chesapeake Bay area (Studholme et al.
1999). As the sea temperature rises, the two groups migrate to their respective spawning
grounds. The northern group moves along the coast of Newfoundland to the southern
Gulf of St. Lawrence (the main spawning area in Canadian waters) arriving between May
and mid-August when the water temperature reaches 9°C with a maximum between 10°C
and 12°C (DFO 2007). Females engage in multiple spawnings and are asynchronous in
timing. The most productive area for spawning is south of the Laurentian Channel and
west of the Magdalen Islands. The southern group spawns in the oceanic bight between
the Chesapeake Bay and southern New England between mid-April and June (Berrien
1982); (Studholme et al. 1999), then continues its migration north to the Gulf of Maine
and Nova Scotia. In the fall, both groups begin their migration back to the over-wintering
grounds. During the spring and fall migrations, mackerel often travel in large schools of
identically sized individuals swimming at the same speed.
Mackerel in the Gulf of St. Lawrence prey mostly on zooplankton both small (copepods,
small crustaceans) and large (euphausiids, hyperiid amphipods, chaetognaths, jellyfish,
mysids, tunicates and ichthyoplankton) along with shrimp and capelin (Savenkoff et al.
2005). Predators of mackerel include cetaceans, seals, large cod and large demersals.
Fishery
Atlantic mackerel have been caught in Canadian waters from as early as the 1800s and
likely even earlier by First Nations peoples (DFO 2007) (Fig. 2). In the 1800s, European
settlers used a variety of methods including beach seines, gillnets, handlines and traps.
These methods were later modified (e.g., traps with bottoms for offshore use and purse
seines using mechanised pulleys) in order to target new areas. Historical catches in
Canada fluctuated due to variations in market demand, the advent of new fishing
methods, harvesting of new areas, natural fluctuations in year-class strength and changes
in migration routes (DFO 2007). Canadian landings stabilized between 1900 and 1938 at
approximately 10,000 mt, then increased during the World War II and later declined
during the 1950s, most likely due to a fungal infection in associated herring populations
(Fig. 2).
8
Atlantic Candian mackerel
120000
March 17, 2011
U.S.A.
110000
CANADA
100000
90000
LANDINGS (t)
80000
70000
60000
50000
40000
30000
20000
10000
0
1800
1810
1820
1830
1840
1850
1860
1870
1880
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
2010
2020
YEAR
Figure 2. Historical Canadian catches of Atlantic mackerel from 1876 to the present day in NAFO subareas
3 and 4 (modified from (Grégoire et al. 2007)
Since the early 1960s, Canadian vessels have caught Atlantic mackerel in NAFO Subarea
3 (the east and south coasts of Newfoundland) and Subarea 4 (Gulf of St. Lawrence and
the Scotian Shelf) with catches in Subareas 2 (east coast of Labrador), 5 and 6 (Gulf of
Maine and Georges Bank) starting in the early 1970s (Grégoire et al. 2000b) (Fig. 3).
During the 1960s, 1970s and 1980s, Canadian catches of Atlantic mackerel increased due
to the strong year-classes from 1967, 1974 and 1982 ((DFO 2007)). Between 1960 and
1994 Canadian landings averaged 18,000 mt per year with the majority (mean ~14,000
mt) coming from Subarea 4. After the introduction of the 200 nautical mile Economic
Exclusion Zone (EEZ) in 1977, catches by Canadian vessels in Subareas 5 and 6 ceased,
although their importance is questionable given that the Canadian fishery was mainly
inshore (François Grégoire, pers. comm.). Declines in catches occurred during the 1990s
but were high during the early and mid-2000s due to the strong 1999 year-class (DFO
2007).
In 2007, in NAFO Subareas 2–6, the total catch was 75,863 mt, which is lower than
catches reported for 2003–2006 (79, 491–110, 286 mt). Almost two-thirds of the catch
originated in Subareas 3 and 4 (50, 578 mt), and this catch has been relatively stable since
2004. Up to 2000, Nova Scotia, Prince Edward Island and Quebec took the largest catch
of mackerel. Since then, Newfoundland and Labrador have exceeded the catches of the
other provinces by a large margin with catches representing 76–82% of the total
Canadian catch in recent years (DFO 2007).
In 2006, in Subareas 3 and 4 (Maritime Provinces, Newfoundland and Labrador, and
Quebec), approximately 10,000 commercial fishermen participated in the mackerel
fishery along with 7,400 personal bait users (DFO 2007). This is an increase from 1997
when 15,000 licenses overall were issued. Up to the year 2000, the majority of the
Canadian catch was taken by gillnets, jiggers and traps. Thereafter, small (<19.8 m) and
large (>19.8 m) purse seines took the lead, being used mostly in Newfoundland. A new
gear type has recently been employed in Newfoundland, a modified version of the bar
seine called the 'tuck' seine. In 2005, tuck seine catches reached 6,393 mt, second only to
purse seine catches (DFO 2007).
9
Atlantic Candian mackerel
March 17, 2011
Figure 3. Map showing NAFO Subareas 2–6 (from http://www.nafo.int)
10
Atlantic Candian mackerel
March 17, 2011
Along the west (NAFO division 4R) and east (3K and 3L) coasts of Newfoundland, the
mackerel season starts in August and extends into November with purse seines being the
main gear type used since 1995 (Grégoire et al. 2007). In the southern Gulf of St.
Lawrence (NAFO division 4T), lines and gillnets are used during the May to October
fishing season. Lines have been replacing gillnets since 1995. Along the Scotian Shelf
(NAFO divisions 4V, 4W and 4X), the trap and gillnet fishing season starts in May and
runs through July; a line fishery operates through the summer into the fall.
The Atlantic mackerel fishery is a competitive fishery managed using a Total Allowable
Catch (TAC) limit that is reviewed annually and shared with management of the US
fishery (DFO 2007). Between 1987 and 2001, the Canadian TAC was set at 100,000 mt
(DFO 2008). After several poor year-classes, the TAC was lowered to 75,000 mt in 2001
and further lowered to 60,000 mt after that (www.dfo-mpo.gc.ca). The TAC is divided
according to vessel size with 60% allocated to inshore vessels (< 19.8 m) and 40% to
larger vessels.
Between 1960 and 1994, foreign vessels caught an average of 81,000 mt per year
(Grégoire et al. 2000a), the majority of which was caught by vessels from the USSR,
Poland and the German Democratic Republic, mostly in NAFO Subareas 5 and 6.
Starting in 1992, fishing by foreign fleets was reduced in Canadian waters and abolished
in the USA. The foreign fleet fishery was most successful in December through May as
Subareas 5 and 6 are the main over-wintering areas for mackerel. Because mackerel seek
deep warm waters during the winter months, bottom trawls and mid-water trawls were
the main types of fishing gear used.
In Canada, the current minimum legal catch size for Atlantic mackerel is 250 mm; it is
prohibited to fish for, buy, sell or possess mackerel less than this minimum legal size.
However, the size prohibition does not apply to undersized mackerel caught during
directed mackerel fishing activities if the number of undersized mackerel caught is less
than 10% of the number of larger mackerel caught (DFO 2007). There is no minimum
legal catch size for mackerel in US waters (François Grégoire, pers. comm., 2009).
Overfishing of Atlantic mackerel occurred during the 1970s when foreign fishing was
extensive and heavy, particularly on Georges Bank and along the New England States,
resulting in annual catches of 300,000–400,000 mt (DFO 2007) (Fig. 4). After the
establishment of the 200 nautical mile EEZ in 1977, a reduction in foreign fishing in US
waters, and its subsequent abolishment in the early 1990s, landings of Atlantic mackerel
have greatly decreased. Nevertheless, catches have shown a recent increase due to
worldwide demand.
11
Atlantic Candian mackerel
March 17, 2011
500000
500000
Foreign
United States
450000
450000
Canada
LANDINGS (t)
400000
400000
TAC
350000
350000
300000
300000
250000
250000
-TAC200000
200000
150000
150000
100000
100000
50000
50000
0
0
1960
1964
1968
1972
1976
1980
1984
1988
1992
1996
2000
2004
YEAR
Figure 4. Annual landings (mt) of Atlantic mackerel and TAC (mt) for the Northwest Atlantic (NAFO
Subareas 2-6) (from (DFO 2008)).
In 2007, northwest Atlantic (NAFO Subareas 2–6) landings totalled 75,863 mt, somewhat
lower than those reported between 2003 and 2006 (79,491–110,286 mt). These are
among the highest catches recorded since the creation of the EEZ (Grégoire et al. 2007,
DFO 2008). This is primarily due to the strong 1999 year-class, which has been the most
productive class in recent years yielding 150,532 mt of fish (Fig. 5). The second most
important year-class was in 1982, yielding a cumulative catch of 65,000 mt (DFO 2008).
However, the 1999 year-class is now contributing little to current catches and stock.
Approximately two-thirds of the 2007 catch (50,578 mt) came from the east coast of
Canada (NAFO Subareas 3 and 4), and this tonnage is similar to that reported since 2004.
Age 1
160000
Ages 1-2
Ages 1-3
140000
Ages 1-4
CATCHES (t)
120000
Ages 1-5
Ages 1-6
100000
Ages 1-7
80000
Ages 1-8
60000
40000
20000
0
1967
1974
1982
1988
1999
2003
2005
STRONG YEAR-CLASS
Figure 5. Cumulative catches (mt) at age for year-classes that dominated the fishery in recent years (from
(DFO 2008))
12
Atlantic Candian mackerel
March 17, 2011
Of the 50,578 mt of mackerel caught in Subareas 3 and 4, 87% (44,032 mt) were landed
in Newfoundland, 5% (2,647 mt) were landed in Nova Scotia, 4% (2,005 mt) were landed
in PEI and the remainder in Quebec and New Brunswick (DFO 2008). Landings in
Newfoundland have shown a dramatic increase since 2000 while those in the other
provinces have been showing a gradual decline (Fig. 6). These changes are likely due to
colder waters in the Gulf of St. Lawrence during spawning leading to changes in
migration routes and spawning locations (DFO 2007). The Canadian landings are likely
to be higher as there are no data on recreational fishing, no dockside monitoring to
minimize unrecorded landings such as bait fishing (except in Nova Scotia and
Newfoundland), and no data on catch sizes of Canadian mackerel caught by US fishers in
NAFO Subareas 5 & 6.
100%
90%
80%
70%
60%
50%
40%
30%
20%
Nova Scotia
New Brunswick
Prince Edward Island
Québec
Newfoundland
10%
0%
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
YEAR
Figure 6. Annual landings (%) of Atlantic mackerel by Canadian province from 1995 to 2006 (modified
from (Grégoire et al. 2007)).
During the period 1977 to 2005, foreign fishing vessels caught 10,990 mt of Atlantic
mackerel offshore on the continental shelf, along its edge and along the east coast of
Cape Breton. The USSR, Cuba, Russia and Bulgaria were responsible for the majority of
this catch with 5,260 mt, 2,062 mt, 1,298 mt and 1,278 mt caught, respectively (Grégoire
2006a). The most intense fishing period was during the early 1990s.
Scope of Recommendation
This report evaluates the ecological sustainability of Atlantic mackerel in Canadian
Waters with a focus on the main fishing areas of NAFO Subarea 3 (east and south coasts
of Newfoundland) and Subarea 4 (Gulf of St. Lawrence and the Scotian Shelf) using the
dominant fishing gear, the purse seine.
13
Availability of Science
Unlike other commercial fish, the abundance of mackerel (and other pelagics) cannot be
assessed using bottom trawl surveys as mackerel use different parts of the water column
varying with the area, time of year and water temperature. Further, catch data are
unreliable as there are no recreational fisheries data, and other than in Nova Scotia and
Newfoundland, there is no dockside monitoring. The abundance of mackerel is therefore
assessed using egg surveys in the southern Gulf of St. Lawrence, the main spawning area
for mackerel in Canadian waters (DFO 2007). Data on the abundance of Atlantic
mackerel eggs have been collected since 1915 although regular and more extensive
surveys did not begin until 1965 (Grégoire 2006b). Between 1983 and 1994, surveys
were conducted annually, on even years between 1996 and 2002 and annually again since
2003 in close cooperation with the Atlantic Zone Monitoring Program (AZMP) (Grégoire
et al. 2006). Data from the egg surveys are used to determine abundance of the Spawning
Stock Biomass (SSB) in the southern Gulf of St. Lawrence and as an index of population
abundance in Canadian waters. Since the introduction of the 200 nautical mile EEZ,
Atlantic mackerel catches by foreign and Canadian vessels along the Scotian Shelf and
Georges Bank have been monitored by the Nova Scotia Observers Program (Grégoire
2006a).
Market Availability
During the early 1990s, the mean value of Canadian landings of Atlantic mackerel was
$7 million; between 2000 and 2005 this increased to $12.7 million (DFO 2007). Until
recently, the USA and Japan have been the most important markets for Canadian
mackerel; however, since the early 2000s, the export of mackerel to China has exceeded
exports to the USA and Japan (Fig. 7). Most Canadian mackerel is exported whole and
frozen to China, Bulgaria, Japan, Romania, the Russian Federation and the USA. Smaller
quantities are exported fresh and whole to the USA and Romania, pickled or cured to the
USA and canned to Lithuania and the Asian markets (DFO 2007). Canada imported close
to 9 million kg (~CA$11.5 million) of mackerel in 2009 and 3.7 million (~CA$6.5
million) in 2010 (www.dfo-mpo.gc.ca).
A number of European mackerel fisheries have recently been certified as sustainable to
the standard of the Marine Stewardship Council (MSC; see http://www.msc.org), a
development that may affect the composition of Atlantic mackerel in the US market.
14
Figure 7. Exports of Canadian mackerel from 2002 to 2006 (from (DFO 2007)).
15
III. Analysis of Seafood Watch® Sustainability Criteria for Wild-caught Species
Criterion 1: Inherent Vulnerability to Fishing Pressure
" Vulnerability depends on the interaction between extrinsic threats and intrinsic ability of
populations to meet the challenges that are imposed" ((Reynolds et al. 2005)).
Atlantic mackerel exhibit biological characteristics that suggest low vulnerability to fishing
pressure (Denney et al. 2002); (Reynolds et al. 2005). The intrinsic rate of increase (‘r’) for
Atlantic mackerel is unknown. Atlantic mackerel is a fast-growing species (von Bertalanffy k
ranging from 0.23 to 0.27) (Froese and Pauly, 2010) reaching its legal catch size (250 mm) by
the end of its second year (Table 1; Fig. 8). Females grow faster than males and individuals in
large year-classes grow more slowly than those in smaller year-classes. The environmental
factors influencing the size of a year-class are unknown.
(A)
450
LENGTH (mm)
400
350
300
250
200
0
2
4
6
8
0
2
4
6
8
10
12
14
16
18
10
12
14
16
18
(B)
SOMATIC WEIGHT (g)
1000
800
600
400
200
0
AGE
Figure 8. Mean length (mm) (A) and somatic weight (g) (B) by age for Atlantic mackerel year-classes sampled
since 1973. Bold lines represent the five largest year-classes that have dominated the fishery in recent years
(modified from (Grégoire et al. 2007)).
16
Sexual maturity is reached early in life and all fish are sexually mature by age four years
with an A50 (the age at which 50% of the population are mature) of 1.9 years (Grégoire et
al. 2007) (Table 1; Fig. 9). The maximum reported age for the species is 17 years (Froese
and Pauly 2010).
1.0
0.9
2000
0.8
2001
PROPORTION
0.7
2002
2003
0.6
2004
0.5
2005
0.4
2006
0.3
0.2
0.1
0.0
0
1
2
3
4
5
6
7
8
9
10
AGE
Figure 9. Mean proportions of mature fish at age calculated during the 2000s using commercial samples of
Atlantic mackerel collected in June and July in NAFO Subareas 3 and 4 (modified from (Grégoire et al.
2007)).
The L50 (the size at which 50% of the population are mature) varies annually and by yearclass (Fig. 10A & 10B). In 2006, the L50 was 251.4 mm and all fish 340 mm and over
were mature. Indeed, since 2000 the annual L50 has been below or slightly above the
minimum legal catch size of 250 mm (Grégoire et al. 2007).The condition of mackerel
changes intra-annually with the lowest values observed in the spring after migration and
spawning and the highest values appearing in the fall. The population structure of
mackerel is characterised by periodic large year-classes that, in some cases, can dominate
the fishery for several years, e.g., the 1999 year-class. Mackerel have high fecundity,
producing around 200,000 larvae per year (Froese and Pauly 2010).
Atlantic mackerel have a wide range, being found in the coastal regions of the North
Atlantic Ocean basin as well as in the Mediterranean and Black Seas. Their range in the
northwest Atlantic extends from North Carolina to the Gulf of St. Lawrence,
Newfoundland and Labrador (DFO 2007). Mackerel spawn along various coastal areas,
but their main spawning ground is in the southern Gulf of St. Lawrence. Recent surveys
have also found significant spawning occurring along the west coast of Newfoundland.
These predictable spawning locations make mackerel an easy target for fisheries. They
are also vulnerable to fishing during the winter months when they congregate along the
edge of the continental shelf in a warm layer, approximately 100 m depth, and become
somewhat sedentary in (François Grégoire, pers. comm.).
17
During the annual spring and fall migrations, mackerel may travel in large schools of
similar sized fish at similar speeds. Once located, these large schools are particularly
vulnerable to fishing predation. However, the timing and path of migrations may vary
with environmental conditions (e.g., water temperature) making the location of mackerel
less predictable.
400
(A)
LENGTH (mm)
350
300
250
200
Minimum legal catch size = 250 mm
150
1970
1975
1980
1985
1990
1995
2000
2005
2010
1995
2000
2005
2010
YEAR
400
(B)
LENGTH (mm)
350
300
250
200
150
1970
1975
1980
1985
1990
YEAR-CLASS
Figure 10. Mean values of L50 by year (A) and year-class (B) from commercial samples of Atlantic
mackerel collected in June and July since 1973 in NAFO Subareas 3 and 4. Vertical lines are 95%
confidence intervals. The current minimum legal catch size is 250 mm (modified from (Grégoire et al.
2007)).
18
Pelagic fish such as mackerel associate with habitats depending on three oceanographic
processes: enrichment (e.g., upwelling), concentration (e.g., convergence that allows food
and larvae to accumulate), and retention of larvae in the stock range or some other
appropriate habitat (e.g., nursery; (DFO 2007)). However, little is known about how these
three processes and types of coastal habitat influence the growth and survival of mackerel
during different life stages.
The estuary and Gulf of St. Lawrence are characterised by large spatial and temporal
variations in environmental conditions and oceanographic processes, and thus they are
likely to contribute to variation in the productivity of mackerel as a result of temperature
fluctuations (DFO 2010). The northern Gulf of St. Lawrence ecosystem has shifted from
one dominated by groundfish and small-bodied forage species to one dominated only by
the latter. In the southern Gulf, the abundance of large-bodied species has declined while
small-bodied taxa have increased (DFO 2010). As a result, the Gulf has become a
favorable environment for spawning mackerel in terms of reduced predator pressure from
groundfish and the availability of prey, although the increase of grey seals in the Gulf
likely reduces mackerel numbers. Similar changes have been observed around the waters
of Newfoundland and along the Scotian Shelf. The degree of hypoxia has increased in the
deep waters of the estuary, and this has had negative effects on the abundance and
diversity of species in the area and may contribute toward poor fish health (DFO 2010).
Substantial recent coastal development may impact the health of mackerel through the
development of aquaculture, introduction of alien invasive species, habitat destruction or
modification and addition of nutrients and contaminants, although knowledge of these
effects and their extent is limited (DFO 2010). Waters around Newfoundland have
experienced dramatic changes in sea temperature, including above-average water
temperatures in the 1950s and 1960s, a cold period during the mid-1980s to early 1990s
and warming since the early 1990s with a 61-year high in sea temperature reached in
2006 (DFO 2010). Water temperatures are important for mackerel and the current warm
waters along west coast of Newfoundland may have contributed to their occurrence.
Mackerel habitat is considered moderately altered by non-fishery impacts.
Table 1. Life history characteristics of male and female Atlantic mackerel (* varies by year) (Studholme et
al. 1999); (Goodwin et al. 2006); (DFO 2007).
Sex
L50,
cm
A50,
yrs
m
f
25.1
1.9
1.9
Growth rates,
Max
von
age, yrs
Bertalanffy k
0.23-0.27
17
Max
size, cm
45
Fecundity
Species range
Special
behavior
200,000
Broad (North
Atlantic,
Mediterranean
and Black Sea)
Schooling;
spawn-ing site
fidelity
19
Synthesis
Atlantic mackerel exhibit biological characteristics that suggest low vulnerability to
fishing pressure. They are a fast-growing species reaching sexual maturity and the current
legal catch size of 250 mm at a young age and exhibiting high fecundity. Each of these
factors receives a ranking of ‘low vulnerability’. Mackerel also have a moderate lifespan,
which receives a ‘moderate vulnerability’ ranking. As may be expected, there is
substantial variation in these life history traits between and within years, and the
environmental factors and processes that may contribute to this variation are not known.
The range of Atlantic mackerel is broad, including the north Atlantic, Mediterranean and
Black Seas, and thus receives a ‘low vulnerability’ ranking. Mackerel spawn in various
coastal areas but their main spawning grounds are in the southern Gulf of St. Lawrence
and more recently along the west coast of Newfoundland, thus making the fish easily
targeted by fisheries. They are also vulnerable to fishing during the winter months when
they congregate along the edge of the continental shelf in a warm layer, at approximately
100 m depth, and become somewhat sedentary in behavior. Mackerel tend to form large
schools during their spring and fall migrations; once located by fishers, large numbers of
mackerel may be caught. However, the timing and path of migration is influenced by
environmental factors that make the location of these schools more difficult to identify.
Little is known about how environmental processes and types of coastal habitat influence
the growth and survival of mackerel during different life stages. The ‘special behaviors or
requirements’ factor receives a ‘moderate vulnerability’ ranking. The habitat of Atlantic
mackerel has undergone major changes in the past few decades with declines in
groundfish, and thus predator pressure from groundfish, increases in seal abundance and
associated predation, coastal development and large fluctuations in sea temperatures.
Some of these changes are likely beneficial to the population while others are likely to be
detrimental. Regardless, the effects are largely unknown and speculative. This factor
receives a ‘moderate vulnerability’ ranking.
Inherent Vulnerability Rank:
Resilient
Moderately Vulnerable
Highly Vulnerable
Criterion 2: Status of Wild Stocks
Factor 1: Management classification status
Atlantic mackerel in the northwest (NAFO Subareas 2–6) are assessed as a single stock
with a geographic range from Labrador to North Carolina. This is because mackerel from
Canadian waters may be fished by the US winter mackerel fishery. The most recent
Canadian stock assessment for Atlantic mackerel was conducted in 2008 based on
spawning stock biomass estimates from the Gulf of St. Lawrence egg survey. The most
recent assessment in the US was conducted in 2005 based on an Age Structured
Assessment Program (ASAP) model. There are sufficient uncertainties in the stock
assessment results that the Transboundary Resource Assessment Committee (TRAC) has
20
“agreed that short-term projections and characterization of stock status relative to
estimated reference points would not be an appropriate basis for management advice at
this time” (TRAC, 2010). Given the reduced productivity and the observation of fewer
older fish both in the NEFSC spring survey and in US commercial catches, the TRAC
recommend that total annual catches should not exceed the mean total landings of 80,000
mt observed over the previous three years (2006–2008) until new data are obtained. The
TRAC considers the status of the Atlantic mackerel in the northwest to be unknown
(TRAC 2010).
Factor 2: Abundance thresholds
Although the TRAC has estimated reference points, it does not recommend their use due
to uncertainties in the stock assessment results (TRAC, 2010). The Spawning Stock
Biomass (SSB) was estimated at 96,968 mt but later adjusted to 153,100 mt due to a
retrospective pattern (TRAC, 2010). A retrospective analysis is a study of successive
estimates of fishery variables (e.g., biomass) as additional years of data are added (Mohn
1999). A retrospective pattern is said to exist when estimates of a given fishing variable
for a given year do not agree and this disagreement shows a systematic pattern of biases
rather than randomness. The SSB40% (a proxy for the SSBMSY) for 2008 was 194,000 mt
and the Maxiumum Sustainable Yield (i.e., yield at F40%) was 37,200 mt. Because the
status of the Atlantic mackerel relative to biomass reference points is considered
unknown (TRAC, 2010), this factor is ranked a ‘moderate’ concern.
Factor 3: Occurrence of overfishing
In 2007, only approximately 30% of the large purse seine vessel TAC was taken while
the majority (93%) of the small vessel TAC was taken. Since 1987, the small vessel TAC
has been exceeded only twice: in 2006 (106%) and in 2005 (109%)(DFO 2008).
The TRAC recommends a management strategy with a low to neutral risk of exceeding
the fishing mortality limit reference point (TRAC 2010). Fishing mortality (F) estimates
for Atlantic mackerel, averaged over ages 4–6 years, showed an increase between 2000
and 2006 from 0.17 to 1.11, followed by a decrease to 0.51 in 2008 (TRAC 2010). The
current F40% (proxy for Fmsy) is at 0.25, F0.1 = 0.29, and F, adjusted for the retrospective
pattern was 0.18 in 2008 (TRAC 2010), below the Fmsy proxy. However, because the
most recent TRAC assessment suggested that biomass and fishing mortality reference
points could not be considered reliable and the status of the stock is considered unknown,
it is uncertain whether overfishing is occurring in this fishery. This factor therefore
receives a ’moderate‘ ranking.
Factor 4: Overall degree of uncertainty in status of stock
The TAC for Atlantic mackerel is shared between Canada and the USA. There is no
distinction in the origin of mackerel stock (i.e., Gulf of St. Lawrence vs. mid-Atlantic
Bight), thus Canadian landings do not include those mackerel of Canadian origin caught
by the US fleet (Grégoire et al. 2007). It is for this reason that Atlantic mackerel are now
being managed as a single stock. Recreational fishing of mackerel (occuring along the
Canadian Atlantic coast during the summer) and mackerel caught for bait are not
recorded and thus are not included in the final landing figures. Further, there is no
21
estimate of recreational or bait fishing included in the assessment when determining the
TAC. Thus, landings of mackerel could be considered largely underestimated. Discards
of undersized (currently < 250 mm) mackerel in the line fishery are also not recorded.
The extent of these discards and the effect they may have on the abundance of fish in the
older-age classes is unknown and difficult to quantify (DFO 2007). Recently, there has
been some concern over changes in the migration routes and spawning areas of mackerel.
Landings along the eastern seaboard of Newfoundland (NAFO divisions 3K and 3L) have
increased in recent years, and this has been accompanied by a decline in landings in the
southern Gulf of St. Lawrence and Scotian Shelf. Plankton surveys in NAFO unit area
4Rc (west of Newfoundland) in 2004 and 2005, and more recently in 2008 (François
Grégoire, pers. comm.), discovered mackerel eggs and larvae, suggesting that substantial
spawning may be occurring in areas other than the southern Gulf of St. Lawrence. These
changes in migration patterns and spawning location may be linked to cooler sea
temperatures recently observed in the Gulf ((DFO 2008); Fig. 11). It has been suggested
that the sampling area for the egg survey be expanded to include the Scotian Shelf and
US waters (Grégoire et al. 2008b). Although a recent stock assessment has been
completed and fishery-independent data are regularly collected, uncertainty in the
validity of the reference points estimated in the stock assessment together with the lack of
data on recreational and bait fishery landings and discards of undersized mackerel places
stock status in the ‘moderate’ concern category.
100
90
80
70
%
60
50
40
30
≥ 9 ºC
20
≥ 10 ºC
10
0
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
YEAR
Figure 11. Surface area (%) in the southern Gulf of St. Lawrence associated with water temperatures > 9°
C and > 10° C as measured during the egg survey (from (DFO 2008)).
Factors 5-6: Short and long-term trends in abundance
The Spawning Stock Biomass (SSB) of mackerel is calculated from annual egg surveys
conducted in the southern Gulf of St. Lawrence. Two methods are used, the Total Egg
Production Method (TEPM) and the Daily Fecundity Reduction Method (DFRM), which
came into use in 1996. The former method is based on estimates of annual egg production
and a density curve describing the proportion of daily egg production based on a logistic
model of the seasonal decline in the gonado-somatic index (DFO 2002). The TEP method
is preferred since the DFR method is resource intensive.
22
Between 2000 and 2005, the 1999 year-class provided the largest proportion of mackerel
landings in NAFO Subareas 3 and 4 (DFO 2008) (Fig. 12). The 1999 year-class
contributed between 63% and 77% of the landings (by number) during the period 2000–
2003. Such strong dominance by a year-class has not been observed since Canada began
collecting data on mackerel landings in 1968. The mean weight of the 1999 year-class is
also among the highest to have been recorded since the late 1960s (Grégoire et al. 2007).
In 2005, the importance of the 1999 year-class was superseded by the 2003 class, which
contributed 32% and 39% of the 2004 and 2005 catch, respectively (DFO 2008).
12
1982
1974
11
1988
1967
10+
9
1999
8
AGE
7
1959
6
2003
5
4
3
2
1
0
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
YEAR
Figure 12. Catch at age (%) of Atlantic mackerel from NAFO Subareas 3 and 4 for the period 1968–2007.
Years identify the class that dominated the fishery. The diameter of the bubble indicates the importance of
the age group (modified from (DFO 2008))
3000000
TEPM
2500000
DFRM
BIOMASS (t)
2000000
1500000
1000000
500000
0
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
2010
YEAR
Figure 13. Spawning stock biomass (mt) of Atlantic mackerel calculated from egg survey data conducted
in the southern Gulf of St. Lawrence. TEPM: Total Egg Production Method; DFRM: Daily Fecundity
Reduction Method (modified from (Grégoire et al. 2008b)).
23
The SSB during the 1990s and 2000s experienced a decline compared with the earlier
period of the 1980s (Fig. 13). This decline in biomass is unlikely due to overfishing but
rather due to the lower water temperatures of the southern Gulf affecting the body
condition of mackerel, the timing of the migration and spawning relative to the time of
the survey, and may indeed affect the path of migration and location of spawning
(Grégoire et al. 2008b). The surface area in the southern Gulf associated with
temperatures greater than 9°C during the sampling period showed a decline between 1983
and 1994. There was an increase in temperature between 1996 and 1998 but a decrease
thereafter.
The SSB has fluctuated slightly but remained fairly flat at low levels since the mid-1990s
(Grégoire et al. 2008b) (Fig. 13).
Factor 7: Current age, size, or sex distribution
Since the late 1990s, there have been few older fish in the NEFSC spring survey and in
commercial catches from the US and Canada. This may be due to older fish being faster
and able to avoid the trawl in the spring survey (TRAC 2010). The abundance of eggs in
the Canadian egg survey in the southern Gulf of St. Lawrence has been low for several
years; a survey of eggs along the Scotian Shelf in 2009 also showed a low abundance. In
Canadian waters since 2000, mackerel have been maturing at shorter lengths and those in
US waters have been maturing at younger ages since 1995. In 2006, landings were
dominated by three year old, four year old and one year old fish from the 2003, 2002 and
2005 year-classes with mean lengths of 33.1 cm, 34.3 cm and 27.6 cm, and weights of
0.43 kg, 0.49 kg and 0.23 kg, respectively (Grégoire et al. 2007). Although there is
evidence for changes in size and age at maturation, it remains unknown whether the age,
size or sex distributions of Atlantic mackerel are skewed relative to their natural
condition due to fishing pressure. This factor receives a ‘moderate’ ranking.
24
Synthesis
There are sufficient uncertainties in the stock assessment that the current status of
Atlantic mackerel is unknown. This factor therefore receives a ‘moderate’ ranking.
Although the TRAC has estimated reference points, it does not recommend their use due
to current uncertainties in the stock assessment results, and thus this factor receives a
‘moderate’ ranking. Atlantic mackerel have not been overfished since the 1970s, which
was due to the large foreign fishing fleet at the time. Since 1987, the small vessel TAC
has been exceeded only twice. Due to uncertainty in catch levels, there was concern that
the TAC for 2008–2009 had been exceeded; the current TAC is now lower at 60,000 mt
and may be adjusted in 2011 depending on catch levels. However, fishing mortality
reference points are highly uncertain and therefore it is unknown whether overfishing is
occurring. This factor receives a ‘moderate’ ranking. There are several areas of
uncertainty in the status of the stock. Recreational and bait fishing are not recorded and
thus not included in final landing figures nor in the determination of the TAC. Discards
of under-sized mackerel in the line fishery are not recorded, and the extent to which this
occurs and its on the abundance of fish in the older age-classes is not known. There has
been some concern over changes in the migration routes and spawning areas of mackerel,
and it has been suggested that the sampling area for the egg survey be expanded to
include the Scotian Shelf and US waters. This factor receives a ‘moderate’ ranking. The
SSB during the 1990s and 2000s experienced a decline compared with the earlier period
of the 1980s, likely due to the lower water temperatures of the southern Gulf rather than
overfishing. The long-term downward trend in population abundance is a high
conservation concern, while the relatively flat trend in the short-term is a moderate
concern. Since the late 1990s, there has been a lack of older fish in the US spring survey
and in commercial catches in the US and Canada. Egg abundance in the Canadian egg
survey for the southern Gulf of St. Lawrence has been low for several years. Mackerel
have been maturing at shorter lengths in Canadian waters since 2000. However, it is
unknown whether the distributions have been skewed due to fishing pressure. This factor
receives a ‘moderate’ ranking. Overall, the stock status of Atlantic mackerel is ranked as
‘moderate’ because many factors are unknown.
Status of Wild Stocks Rank:
Healthy
Moderate/Rebuilding
Poor
Critical
25
Criterion 3: Nature and Extent of Bycatch
Bycatch is defined as species that are caught but subsequently discarded (injured or
dead) for any reason. Bycatch does not include incidental catch (non-targeted catch) if it
is utilized, accounted for and/or managed in some way.
Factor 1: Quantity and composition of bycatch
The majority of Atlantic mackerel in Canadian waters are caught using purse seines;
fewer are caught with gillnets, traps and handlines (Fig. 14A). Small purse seine vessels
(< 19.8 m) account for the majority of mackerel caught, followed by large purse seiners
(Fig. 14B).
(A)
(A)
Gillnet
Gillnet
2%
2%
Jigger
Jigger
3%
3%
Trap
Trap
3%
3%
Tuck-Ring Seine
Tuck-Ring
0% Seine
0%
Other
Other
1%
1%
Purse Seine > 19.8 m
Purse Seine > 65'
16%
16%
Purse Seine < 19.8 m
Purse Seine
76%< 65'
76%
(B)
(B)
LANDINGS
LANDINGS
(t) (t)
40 000
40 000
35 000
35 000
30 000
1995-2005 Average
1995-2005 Average
2006
2006
28 970 t
28 970 t
30 000
25 000
25 000
20 000
20 000
15 000
15 000
10 000
105 000
000
5 0000
0
Traw l
Midw ater
Tuck-Ring
Purse
Purse
Other
Gillnet
Trap
Longline
Handline
Jigger
Weir
Other
Unknow n
Traw l
traw l
Midw ater
Seine
Tuck-Ring
Gillnet
Trap
Longline
Handline
Jigger
Weir
Other
Unknow n
Seine
Seine >
Pursem
19.8
Seines
Other
traw l
Seine <
Pursem
19.8
Seine < 65' Seine > 65'
Seines
GEAR
GEAR
Figure 14. Canadian landings (%) of Atlantic mackerel by fishing gear in 2006 (A) and annual means (mt)
for 1995–2005 (B) (modified from (Grégoire et al. 2007)).
The mackerel fishery along the coasts of Newfoundland mostly uses purse seining and
has done so since 1995 (Grégoire et al. 2007). Mackerel caught in NAFO division 4T
(Gulf of St. Lawrence) are mostly caught with lines (including handlines and jiggers) and
early in the season with gillnets (both fixed and drift). On the Scotia Shelf (NAFO
divisions 4X, 4V and 4W), purse seines, traps, lines and gillnets are used with traps
26
replacing gillnets since 1995 (Grégoire et al. 2007). There is a small mackerel fishery
using gillnets in parts of the Quebec Lower North Shore.
During the 1977 and 2005 period, foreign vessels used mostly bottom otter trawls (55%
of the catch by weight) and midwater trawls (44% of the catch by weight) with the
remainder using purse seines. Overall, the purse seine is the dominant method of fishing
for Atlantic mackerel in Canadian waters. This section on the nature and extent of
bycatch will focus on the purse seine.
As this fishery lacks onboard observers, no data are available on bycatch in the Canadian
Atlantic mackerel fishery (François Grégoire, pers. comm.). However, purse seining is a
relatively specific method of fishing since the nets are set after the target fish has been
located, thus reducing the amount of bycatch (Chuenpagdee et al. 2003). In a report
examining the collateral damage of fishing methods, purse seining received the lowest
score when compared with other methods of fishing (Chuenpagdee et al. 2003).
However, in the Gulf of Maine purse seine herring fishery (herring is a pelagic schooling
species similar to mackerel), marine mammals have been taken as bycatch, including the
humpback whale (Megaptera novaeangliae) and fin whale (Balaenoptera physalus), both
of which are listed under the Endangered Species Act (Zollett 2009).
Bycatch in the Atlantic mackerel fishery may also include depleted species of river
herring. In the United States, river herring, which includes blueback herring (Alosa
aestivalis) and alewife (Alosa pseudoharengus), have been declared Species of Special
Concern because of drastic declines in stocks (Haas-Castro 2006). The reasons for these
declines are not fully understood. The US National Marine Fisheries Service (NMFS)
states that a lack of understanding of bycatch of river herring in ocean fisheries, among
other factors, is inhibiting a clear understanding of the reasons for this species’ decline
(NMFS 2007). Bycatch of these species has been documented in the US Atlantic
mackerel fishery (MAFMC 2008), and the distributions of these species extend into
Canada (Stone and Jessop 1992). However, the occurrence, frequency and extent of river
herring bycatch in the Atlantic mackerel fishery are not known. The US fishery uses midwater trawl gear while the Canadian fishery primarily uses purse seine gear, so it is
possible that river herring bycatch is avoided in the Canadian fishery due to the greater
selectivity of the gear.
Factor 2: Population consequences of bycatch
The consequences of bycatch on populations are unknown since no observer program
exists to document the bycatch. However, given that purse seines have a low level of
bycatch (Chuenpagdee et al. 2003), one would expect the impact on populations to be
low. Bycatch of protected or depleted species such as marine mammals and river herring
is not known to occur at rates high enough to contribute to population declines in these
species.
Factor 3: Trends in interaction bycatch rates
Trends in interaction bycatch rates are unknown due to the lack of bycatch data available
sin the absence of an observer program.
27
Factor 4: Ecosystem impacts
The ecosystem impacts of bycatch in the mackerel fishery are unknown due to the lack of
available bycatch data. Purse seines are known to have low bycatch rates and thus are
likely to have a low impact on the ecosystems in which they are used.
Synthesis
The purse seine is the dominant method of fishing Atlantic mackerel in Canadian waters.
Due to the absence of an observer program, no data are available on the quantity or
composition of bycatch, although purse seines are known to have low bycatch rates. Due
to the lack of available data, this factor receives a ‘moderate’ ranking. The consequences
of bycatch on the population and trends in bycatch interaction rates are unknown, thus
these two factors receive ‘moderate’ rankings. The impacts of bycatch on the ecosystem
are assumed to be low given the low bycatch rates of purse seines, however, without
knowledge of the species affected, this factor receives a ‘moderate’ ranking. Overall, the
lack of data on bycatch in the fishery results in a ‘moderate’ ranking.
Nature of Bycatch Rank:
Low
Moderate
High
Critical
28
Criterion 4: Effect of Fishing Practices on Habitats and Ecosystems
Factor 1: Impacts of fishing gear on habitat
More than three-quarters of Atlantic mackerel in Canadian waters are caught using purse
seines and the majority of the remainder are caught using other seines. As this type of
fishing gear does not come into contact with the seafloor, the impact on the benthic
habitat is minimal (Chuenpagdee et al. 2003).
Factor 2: Resilience of the habitat fished
Purse seines have minimal impact on the habitat as they do not make contact with the
seafloor, thus the resilience of the habitat is not relevant.
Factor 3: Spatial extent of the impact
The spatial extent of the impact is not relevant as purse seines have minimal impact on
the habitat.
Primary Ecosystem Factors
Factor 1: Disruption of food webs
Atlantic mackerel is one of the main forage species in the Gulf of St. Lawrence and the
northwest Atlantic (Savenkoff et al. 2005). The main predators of Atlantic mackerel have
remained the same despite ecosystem changes occurring since the 1980s (see below);
however, their ranking has changed (Fig. 15). Currently, fishing incurs the greatest
mortality followed by cetaceans and pinnipeds whereas during the 1980s large cod were
responsible for the highest mortality. If mackerel stocks are overfished, there may be
implications for these marine mammals. Although marine mammals are capable of
modifying their diet according to prey availability, cumulative decreases in stock sizes
across multiple fisheries could affect them negatively (Kaschner et al. 2001).
Figure 15.
Causes of
mackerel
mortality in the
southern Gulf of
St. Lawrence
from the 1980s
to mid 1990s
(from
(Savenkoff et al.
2005)).
29
Factor 2: Changes in ecosystem state
The Gulf and areas of the northwest Atlantic have undergone large ecosystem changes
since the 1980s, partly due to the overfishing of large demersals such as cod (Gadus
morhua), switching from a system dominated by large demersals to one dominated by
small pelagics. However, fishing for mackerel did not contribute to these ecosystem state
changes.
Synthesis
The majority of Atlantic mackerel in Canadian waters are caught using purse seines,
which have minimal impact on the seafloor habitat given that there is no physical contact.
Thus, the effect of fishing gear on the habitat receives a ‘benign’ ranking. Atlantic
mackerel is an important forage species for several species of marine mammal, although
the greatest current source of mortality is from fishing. Marine mammals are able to
adapt to changes in prey availability, although they may be negatively affected if multiple
forage stocks decline. Due to uncertainty around the disruption of food webs as a result of
mackerel fishing, this factor receives a ‘moderate’ ranking. There have been major
changes in the state of the ecosystem—partly due to the overfishing of cod and other
large demersals—which caused a switch in the ecosystem from one dominated by large
demersals to one dominated by small pelagics. However, these changes in ecosystem
state were not directly related to the fishing of mackerel and thus this factor receives a
‘benign’ ranking. Overall, the habitat and ecosystem effects of the mackerel fishery are
considered ’benign‘ because gear impacts are minimal and there is no evidence of food
web effects or ecosystem state changes.
Effect of Fishing Practices Rank:
Benign
Moderate
Severe
Critical
30
Criterion 5: Effectiveness of the Management Regime
Factor 1: Stock assessments
Stocks of Atlantic mackerel are assessed using egg surveys, primarily conducted in the
southern Gulf of St. Lawrence, one of the main spawning areas in Canadian waters. Data
from the egg surveys are used to calculate the SSB in the southern Gulf of St. Lawrence
and an index of population abundance for Canadian waters as a whole. In 2004 and 2005,
the Department of Fisheries and Oceans conducted a capelin and herring larval survey
along the west coast of Newfoundland and sampled eggs and larvae from other species,
including Atlantic mackerel (Grégoire et al. 2008a). Much to their surprise, the data
revealed that, although mackerel were few in number, significant spawning was taking
place along this coastline. With growing concern that the area covered by the current egg
survey no longer represented the whole of the spawning area for mackerel in eastern
Canada, a recent mackerel egg survey was expanded to include waters beyond the Gulf of
St. Lawrence (Grégoire et al. 2008b) (François Grégoire, pers. comm.). In Europe, an
international egg survey is conducted every three years to estimate spawning biomass and
calibrate sequential population analyses (Grégoire et al. 2007). The most recent Canadian
stock assessment for Atlantic mackerel was conducted in 2008. Plankton surveys in
NAFO unit area 4Rc (west of Newfoundland) in 2004, 2005 and 2008 suggest that
substantial spawning may be occurring in areas other than the southern Gulf of St.
Lawrence. It has been suggested that the sampling area for the egg survey be expanded to
include the Scotian Shelf and US waters (Grégoire et al. 2008b) in order to achieve a
more representative estimate of the Spawning Stock Biomass.
Although regular stock assessments are conducted, the most recent transboundary
assessment (TRAC, 2010) highlighted substantial uncertainties in the assessment and
rendered the estimate reference points unreliable. Therefore, the TRAC considers the
stock status unknown. As such, this factor is considered a ’moderate‘ concern because
there is a stock assessment available but it is highly uncertain.
Factor 2: Scientific monitoring
The spawning stock of Atlantic mackerel has been monitored since as early as 1915,
although regular and more extensive surveys did not begin until 1965 (Grégoire 2006b).
Between 1983 and 1994, egg surveys were conducted annually, on even years between
1996 and 2002, and annually since 2003 in close cooperation with the Atlantic Zone
Monitoring Program (AZMP) (Grégoire et al. 2006). Fishery-dependent data are used to
monitor the performance of the fishery, e.g., dockside monitoring, at-sea observers, etc.
(DFO, 2007).
Stock discrimination studies would be necessary to determine the origin of mackerel
fished by Canadian and American fleets. These would contribute toward a precautionary
approach through the development of a Sequential Population Analysis and the
calculation of a minimum biomass limit (Grégoire and Savenkoff 2005).
31
Factor 3: Scientific advice
Since 1987, Canada has proposed that the Atlantic-wide TAC be shared with the US
(Grégoire et al. 2007). The Canadian quota is reviewed annually and adjustments are
made according to scientific recommendations and consultations with industry. In 2001,
the Canadian TAC (previously at 100,000 mt) was revised to 75,000 mt after a series of
low SSB estimates from the 1996, 1998 and 2000 egg surveys. In contrast, the US quota
is revised annually according to estimates of biomass, anticipated Canadian landings and
other factors. The most recent Canadian TAC is 60,000 mt divided according to the size
of vessel with 60% allocated to purse seine vessels (< 19.8 m) or those using traps,
gillnets, lines or weirs and 40% to larger (> 19.8 m) purse seine vessels (www.dfompo.gc.ca). The Atlantic Mackerel Advisory Committee (AMAC) has recently accepted
a flexible approach to allocating the TAC between the small inshore and larger offshore
vessels, "…if the less than 65’ fleets reach their allocation (i.e., 60% of TAC)
and uncaught quota remains within the greater than 65’ fleet allocation, consideration
may be given to allow the less than 65’ fleets to continue fishing within the overall TAC"
(DFO 2007).
Several previously ignored issues have been raised over a number of years in stock
assessment reports concerning management of the Canadian mackerel stock. These
include estimating catches from bait and recreational fishermen, discards of small
mackerel caught on lines in the Gulf of St. Lawrence, extending the egg survey beyond
the Gulf of St. Lawrence and determining the origin of mackerel stocks fished by the
Canadian and American fleets. Due to the absence of action on some of these measures, it
has been suggested in several recent assessment reports that the mackerel catch is likely
underestimated. This is of particular concern since the historically large 1999 year-class
is no longer contributing toward catches (Grégoire et al. 2007). Given the departure of the
1999 year-class and the current high catches, the TAC has been lowered to 60,000 mt for
2010–2011 (www.dfo-mpo.gc.ca). If the catches in 2010 exceed 50,000 mt, there will be
further discussion as to whether the TAC will be reduced.
There have been some recent improvements in these areas of concern based on the
scientific advice given in DFO Research Documents and Stock Status Reports. In 2007,
Newfoundland and Labrador introduced a dockside monitoring program for all
commercial small pelagics, including mackerel, and it is expected that these data will be
used for quota management and stock assessment purposes (DFO 2007). The DFO is
investigating the use of a marine recreational fishing license for Atlantic mackerel as a
means to monitor catch levels (DFO 2007). Canada has been in discussion with the US to
develop an Atlantic mackerel joint working group to aid cooperation and management of
the northwest Atlantic stock (DFO 2007). The report also notes that "…a better
understanding of the mackerel biomass and distribution in the waters of both countries is
needed. As a first step, Canada is exploring the possibility of a common egg survey in
both US and Canadian waters to obtain the necessary information." In 2010, the first joint
Canada/USA Transboundary Resources Assessment Committee assessment was
conducted (TRAC 2010). Given the current high catches of mackerel, the uncertainty of
the SSB and unrecorded catches (from bait and recreational fishermen), the DFO
32
implemented a freeze on new authorizations of mobile gear for Atlantic mackerel (DFO
2007) in 2007 and has lowered the TAC.
Overall, management has complied with scientific recommendations when setting the
quota for the Atlantic mackerel fishery.
Factor 4: Management plans to control bycatch
Mesh size for fishers using gillnets is restricted (mesh size ≤ 83 mm) along with the use
of monofilament in gillnets (DFO, 2007). Further restrictions are in place according to
the province. In Quebec, to limit the bycatch of salmon, there are specific provisions for
fishers using traps and gillnets. In Newfoundland and Labrador, trapnet leaders of mesh
size 2–7” are prohibited as is the use of monofilament material in trapnet leaders. These
regulations, combined with the use of purse seines, which generally result in low bycatch
when set directly on schooling fish, are considered effective means of mitigating bycatch.
Factor 5: Management plans to control habitat impacts from fishing practices
Given the low habitat impact of gear used in this fishery, there are no plans to control
habitat impacts due to fishing practices. This factor is considered ‘not applicable’ because
habitat impacts are benign.
Factor 6: Catch monitoring and enforcement
Currently, monitoring of the Canadian Atlantic fishery is achieved through dockside
monitoring in Nova Scotia and more recently in Newfoundland and Labrador, at-sea
observers, hails of departures and arrivals, buyer hails and purchase slips sent to
processing plants, along with the submission of logbooks (DFO, 2007). It has been
suggested that catch monitoring could be improved by installing a requirement for all
fishermen (including bait fishermen) to complete logbooks of their catches or to extend
dockside monitoring to all provinces. However, it has been noted that there are flaws in
the use of logbooks since in some parts of Nova Scotia official statistics are lower than
catches reported by fishermen (Grégoire et al. 2007). The amount of mackerel taken in
the bait fishery and by recreational fishers is not recorded, nor are those mackerel from
Canadian waters that are caught by American fleets on the Georges Bank. Although the
contributions of individual recreational fishers are relatively harmless, together they may
constitute a significant fishery given that it occurs each summer and all along the eastern
Canadian coast. The US produces estimates of catches from recreational fishers (Grégoire
and Savenkoff 2005), although only from chartered vessels; mackerel caught at wharfs
during the summer are not recorded (François Grégoire, pers. comm.).
In recent years, in the southern Gulf of St. Lawrence, it has been noted that large numbers
of small mackerel (below the minimum legal size) are being discarded in the handline
fishery. The mortality rate of discarded fish is difficult to quantify. However, the amount
of discards should be monitored given the predominance of the handline fishery in the
southern Gulf during the fall (DFO 2007).
Approximately 2,370 fishery officer hours were dedicated to the Atlantic mackerel
fishery in all areas in 2007, which shows an increase from 2001 (DFO 2007). Fishery
33
officers are involved in small vessel patrols and landings checks. The mackerel fishery is
also monitored using aerial surveillance, although this is mostly ancillary to patrols for
other activities. Fisheries officers are involved in several enforcement issues and their
strategies are outlined in Table 2. The majority of violations are related to possession of
the appropriate registration and licenses (Table 3).
Table 2. Enforcement Issues and Strategies (from (DFO 2007)).
Issue
Enforcement Strategy
Fishing during closed Air surveillance/vessel patrols of Fishing Areas; investigation of
time/in closed area complaints and follow up with appropriate action.
Bycatch of salmon At sea checks to observe bycatch, mesh size requirements and
and groundfish in
overall compliance with conditions of licence; deployment of
pelagic traps
observers to monitor fishery; dockside monitoring of catch;
Undersize mackerel At sea checks to sample mackerel to ensure size requirements are
met; deployment of observers to conduct random sampling;
dockside monitoring; recommend closure of fishery if large
Any conservationProactive communications strategy, publishing convictions for
related offence
conservation related offences and encourage courts to impose fines
that will provide for an adequate deterrent.
Table 3. Violations from the Atlantic mackerel fishery during the period 2002–2007 (from (DFO 2007)).
VIOLATION TYPE
2002 2003 2004 2005 2006 2007
Area / Time
0
1
1
0
2
0
Assault / Obstruction
Gear–Illegal / Used
Illegally
Illegal buy /sell /
possess
Registration / Licence
0
2
0
0
3
0
1
2
2
3
2
0
1
0
1
1
22
3
46
19
10
7
19
16
Reporting
0
0
0
2
2
0
Size Limit
0
0
0
0
2
0
34
Although there have been some citations, violations are rare and regulations have been
enforced by independent bodies. Enforcement is therefore considered a low conservation
concern.
Factor 7: Management track record
The Atlantic mackerel stock has not been overexploited since the 1970s when foreign
fleets were prominent; this is due to prohibition of foreign fleets in American waters and
a reduction in the foreign fleet in Canadian waters. Since 1987, the small vessel TAC has
been exceeded only twice (2006, 106% and 2005, 109%; (DFO 2008)). Given the
uncertainty in the SSB and unrecorded catches, there was growing concern that catches
were approaching or exceeding the TAC. In response, in 2010 the TAC was lowered to
60,000 mt (www.dfo-mpo.gc.ca). In several previous years, the TAC has been adjusted in
response to low estimates of SSB. For example, in 2001 after several years of low SSB
due to poor year-classes, the TAC was lowered from 100,000 mt to 75,000 mt (DFO,
2007). Since 2007, authorizations for new mobile gear activities to fish for Atlantic
mackerel have been frozen. Management’s track record is considered a moderate
conservation concern because stock productivity has varied, but management has
responded appropriately to declines in abundance.
35
Synthesis
Stock assessments of Atlantic mackerel, based on egg surveys in the Gulf of St.
Lawrence, have been conducted on a regular basis since the 1960s and on an annual basis
since 2003. From these surveys, a spawning stock biomass is calculated and an index of
population abundance for Canadian waters is derived. Although stock assessments are
conducted regularly, due to the high uncertainty in the most recent transboundary
assessment, this factor is a moderate conservation concern. The spawning stock in the
Gulf of St. Lawrence has been monitored since 1915. Stock discrimination studies are
required to determine the origin of mackerel fished by the Canadian and American fleets.
This factor is a low conservation concern. Scientific advice has been given on the issues
above and others such as monitoring recreational activities, extending the current range
of the egg survey and lowering the TAC. There has been some discussion about making
these changes while others, such as extending the geographical range of the egg survey, a
freeze on new authorizations for mackerel gear and lowering the TAC, have already been
heeded. This factor is a low conservation concern. There are management plans in place
to control bycatch, varying by province, such as limits on mesh size and the use of
monofilament in gillnets and trapnets. Given that the majority of mackerel is caught using
purse seines and restrictions are in place on the use of other gear types, this factor is a
low conservation concern. The fishing gear used in Canadian waters consists mostly of
purse seines, which have minimal impact on the environment, so management efforts to
reduce habitat impacts are not needed. Monitoring of the commercial catch needs to be
improved and monitoring for the bait and recreational fisheries need to be launched. The
DFO does have independent enforcement strategies in place for fishery violations. This
factor is a low conservation concern. Atlantic mackerel have not been overexploited since
the 1970s when foreign fleets were prominent. With concern over the inaccuracy of the
SSB and no monitoring of bait or recreational fishers, the TAC was lowered in 2010 and
new authorizations on mackerel gear have been frozen. This factor is a moderate
conservation concern, because while productivity has varied, management has responded
quickly. Due to regular assessment of the fishery using fishery-independent data,
adherence to scientific advice, effective bycatch mitigation, and enforcement of
regulations, management of the Atlantic mackerel fishery is considered highly effective.
Effectiveness of Management Rank:
Highly Effective
Moderately Effective
Ineffective
Critical
36
IV.
Overall Evaluation and Seafood Recommendation
Atlantic mackerel exhibit biological characteristics that suggest low vulnerability to
fishing pressure. They are a fast-growing species that reach sexual maturity and the
current legal catch size of 250 mm at a young age, exhibit high fecundity, have a
moderate lifespan and a broad range in the North Atlantic. Mackerel are vulnerable to
fishing during spawning and the winter months as well as during the spring and fall
migration, although the timing and path of migration vary, making location of these
schools more difficult. Atlantic mackerel are thus considered ‘inherently resilient’ to
fishing pressure.
Atlantic mackerel abundance and fishing pressure relative to reference points are
unknown due to substantial uncertainties in the most recent stock assessment. As a result
of the high uncertainty and many unknown factors, the stock status of Atlantic mackerel
is a moderate conservation concern.
The purse seine is the dominant method of fishing Atlantic mackerel in Canadian waters.
Due to the absence of an observer program, no data are available on the quantity and
composition of bycatch, although purse seines typically have low bycatch rates. The
consequences of bycatch on the population, trends in interaction bycatch rates and the
impact on the ecosystem are all unknown. Given this absence of data, the nature and
extent of bycatch are considered ’moderate’.
Purse seine fishing gear has minimal impact on the seafloor habitat given that there is no
physical contact. Atlantic mackerel is an important forage species for several species of
marine mammal, although the greatest current source of mortality is from fishing. Marine
mammals are able to adapt to changes in prey availability, although they may be affected
negatively if multiple forage stocks decline. There have been major changes in the state
of the ecosystem; however, these changes were not directly related to the fishing of
mackerel. Consequently, the effect of fishing practices on habitats and ecosystems is
considered ‘benign’.
Stock assessments of Atlantic mackerel have been conducted on a regular basis since the
1960s and on an annual basis since 2003. However, the current stock status is highly
uncertain. The mackerel spawning stock has been monitored since 1915. Scientific advice
has been given on the issues above (amongst others) with various degrees of adoption,
but managers generally do not exceed catch quotas recommended by scientists. Effective
regulations are in place to control bycatch. Efforts to reduce habitat impacts are not
required given the low impact of the fishing gear. Catch monitoring of the commercial
and recreational fisheries needs improvement, but enforcement strategies are in place for
fishery violations. Atlantic mackerel has not been overexploited since the 1970s,
although there is concern over the stock assessments and the lack of monitoring. The
management regime is considered ‘highly effective’ due to regular collection of scientific
data, compliance with scientific advice on catch quotas, effective enforcement and
mitigation of bycatch concerns.
37
Overall, due to its low inherent vulnerability, benign impact on the habitat and
ecosystem, and highly effective management, the Atlantic mackerel fishery is a ‘Best
Choice’.
Table of Sustainability Ranks
Sustainability Criteria
Inherent Vulnerability
Low
Critical
√
√
√
Status of Stocks
Nature of Bycatch
Habitat & Ecosystem
Effects
Management Effectiveness
Conservation Concern
Moderate
High
√
√
Overall Seafood Recommendation:
Best Choice
Good Alternative
Avoid
38
Acknowledgements
Seafood Watch and SeaChoice gratefully acknowledge François Grégoire (DFO, Quebec)
and one anonymous reviewer for their valuable input and comments on this report.
Scientific review does not constitute an endorsement of the Seafood Watch® program, or
its seafood recommendations, on the part of the reviewing scientists. Seafood Watch®
and SeaChoice are solely responsible for the conclusions reached in this report.
39
V.
References
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R. Azarovitz, editors. Fish distribution. N.Y. Sea Grant Institute, Albany, NY.
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Fish and Wildlife Service 53:60-74.
Chuenpagdee, R., L. E. Morgan, S. M. Maxwell, E. A. Norse, and D. Pauly. 2003. Shifting gears:
assessing collateral impacts of fishing methods in US waters. Frontiers in Ecology and the
Environment 1:517-524.
Collette, B. B., and C. E. Nauen. 1983. FAO species catalogue Vol 2. Scombrids of the world. An
annotated and illustrated catalogue of tunas, mackerels, bonitos and related species known to
date. FAO Fish. Synop 125:137.
Denney, N. H., S. Jennings, and J. D. Reynolds. 2002. Life history correlates of maximum
population growth rates in marine fishes. Proceedings of the Royal Society of London. Series B:
Biological Sciences 269:2229-2237.
DFO. 2002. Atlantic mackerel of the northwest Atlantic - Update 2001. B4-04.
DFO. 2007. Integrated Fisheries Management Plan: Atlantic Mackerel. http://www.dfompo.gc.ca/communic/fish_man/ifmp/mackerel-maquereau/index_e.htm.
DFO. 2008. Assessment of the Atlantic mackerel stock for the northwest Atlantic (Subareas 3 and
4) in 2007. 2008/041.
DFO. 2010. 2010 Canadian marine ecosystem status and trends report. 2010/030.
Goodwin, N. B., A. Grant, A. L. Perry, N. K. Dulvy, and J. D. Reynolds. 2006. Life history
correlates of density-dependent recruitment in marine fishes. Canadian Journal of Fisheries and
Aquatic Sciences 63:494-509.
Grégoire, F. 2006a. Data update on the Atlantic mackerel (Scomber scombrus L.) fishery covered
by the Nova Scotia Observer Program (1977-2005). 2006/096.
Grégoire, F. 2006b. Distribution and abundance of the Atlantic mackerel (Scomber scombrus L.)
eggs and larvae from the ichthyoplankton surveys conducted in the southern Gulf of St.
Lawrence between 1965 to 1975. 2006/098.
Grégoire, F., W. Barry, J. Barry, O. Gregan, C. Lévesque, J.-L. Beaulieu, and M.-H. Gendron.
2008a. Assessment of the Atlantic mackerel (Scomber scombrus L.) spawning stock biomass
from the data of the ichthyoplankton surveys made on the west coast of Newfoundland in 2004
and 2005. 2008/039.
Grégoire, F., D. Bernier, and S. Hurtubise. 2000a. Update (1960-1994) of the Atlantic mackerel
(Scomber scombrus L.) catches made by foreign vessesl in NAFO subareas 3 to 6. Pages 31-50 in
F. Gregoire, editor. The Atlantic mackerel (Scomber scombrus L.) of NAFO sub-areas 2 to 6.
Canadian Science Advisory Secretariat, Research Document. 2000/021.
40
Grégoire, F., D. Bernier, and S. Hurtubise. 2000b. Update (1960-1994) of the Canadian Atlantic
mackerel (Scomber scombrus L.) catches for NAFO subareas 2 to 6 and sub-division 5Zc. Pages
7-30 in F. Gregoire, editor. The Atlantic mackerel (Scomber scombrus L.) of NAFO sub-areas 2
to 6. Canadian Science Advisory Secretariat, Research Document 2000/021.
Grégoire, F., C. Lévesque, J.-L. Beaulieu, and M.-H. Gendron. 2008b. Results of the Atlantic
mackerel (Scomber scombrus L.) egg survey conducted in the southern Gulf of St. Lawrence in
2007. 2008/081.
Grégoire, F., C. Lévesque, J.-L. Beaulieu, and J. Hudon. 2006. Assessment of the Atlantic
mackerel (Scomber scombrus L.) spawning stock biomass from the 2003, 2004, and 2005 egg
surveys.
Grégoire, F., C. Lévesque, J.-L. Beaulieu, C. Méthot, and M.-H. Gendron. 2007. Atlantic
mackerel (Scomber scombrus L.) fishery and biology for NAFO Subareas 3 and 4 in 2006.
2007/067.
Grégoire, F., and C. Savenkoff. 2005. Atlantic mackerel (Scomber scombrus L.) fishery, biology,
diet composition and predation in NAFO Subareas 3 and 4 in 2004. 2005/056.
Haas-Castro, R. 2006. Status of fisheries resources of the northeastern US. Available at:
http://www.nefsc.noaa.gov/sos/spsyn/af/herring.
Kaschner, K., R.Watson, V. Christensen, A. W. Trites, and D.Pauly. 2001. Modeling and
mapping trophic overlap between marine mammals and commercial fisheries in the North
Atlantic. Pages 35-45 in D. Zeller, R. Watson, and D. Pauly, editors. Fisheries Impacts on North
Atlantic Ecosystems: Catch, Effort, and National/Regional Data Sets. Fisheries Centre, University
of British Columbia, Canada.
MAFMC. 2008. Mid-Atlantic Fisheries Management Council. “Amendment 10 to The Atlantic
Mackerel, Squid, and Butterfish Fishery Management Plan Including Draft Supplemental
Environmental Impact Statement and Essential Fish Habitat Assessment.” March 5, 2008. MidAtlantic Fishery Management Council in cooperation with NMFS.
Mohn, R. 1999. The retrospective problem in sequential population analysis: An investigation
using cod fishery and simulated data. ICES Journal of Marine Science 56:473-488.
NMFS. 2007. National Marine Fisheries Service. “NOAA National Marine Fisheries Service.
Species of Concern. River Herring (Alewife and Blueback herring).” Accessed on August 5,
2008. <http://www.nmfs.noaa.gov/pr/pdfs/species/riverherring_detailed.pdf>.
Reynolds, J. D., N. K. Dulvy, N. B. Goodwin, and J. A. Hutchings. 2005. Biology of extinction
risk in marine fishes. Proceedings of the Royal Society B: Biological Sciences 272:2337–2344.
Savenkoff, C., F.Grégoire, M.Castonguay, D.P.Swain, D. Chabot, and J. M. Hanson. 2005. Main
prey and predators of Atlantic mackerel (Scomber scombrus L.) in the northern and southern Gulf
of St. Lawrence during the mid-1980s, mid-1990s, and early 2000s. Canadian Technical Report
of Fisheries and Aquatic Sciences 2619:29.
Sette, O. E. 1950. Biology of Atlantic mackerel (Scomber scombrus) of North America. Part II.
Migrations and habits. U.S. Fish and Wildlife Service Fishery Bulletin 51:251-358.
41
Stone, H., and B. Jessop. 1992. Seasonal distribution of river herring Alosa pseudoharengus and
A. aestivalis off the Atlantic coast of Nova Scotia. . Fishery Bulletin 90:376-389.
Studholme, A. L., D. B. Packer, P. L. Berrien, D. L. Johnson, C. A. Zetlin, and W. W. Morse.
1999. Essential fish habitat source document: Atlantic mackerel, Scomber scombrus, life history
and habitat characteristics 141.
TRAC. 2010. Atlantic Mackerel in the Northwest Atlantic. 2010/01.
Zollett, E. A. 2009. Bycatch of protected species and other species of concern in US east coast
commercial fisheries. Endangered Species Research 9:49.
42
Species: Atlantic mackerel
Region: Atlantic Canada
Analyst: Damian Lidgard
Date: March 17, 2011
Seafood Watch™ defines sustainable seafood as originating from sources, whether fished1 or
farmed, that can maintain or increase production in the long-term without jeopardizing the
structure or function of affected ecosystems.
The following guiding principles illustrate the qualities that capture fisheries must possess to be
considered sustainable by the Seafood Watch program. Species from sustainable capture
fisheries:
• have a low vulnerability to fishing pressure, and hence a low probability of being
overfished, because of their inherent life history characteristics;
• have stock structure and abundance sufficient to maintain or enhance long-term fishery
productivity;
• are captured using techniques that minimize the catch of unwanted and/or unmarketable
species;
• are captured in ways that maintain natural functional relationships among species in the
ecosystem, conserves the diversity and productivity of the surrounding ecosystem, and do
not result in irreversible ecosystem state changes; and
• have a management regime that implements and enforces all local, national and
international laws and utilizes a precautionary approach to ensure the long-term
productivity of the resource and integrity of the ecosystem.
Seafood Watch has developed a set of five sustainability criteria, corresponding to these guiding
principles, to evaluate capture fisheries for the purpose of developing a seafood recommendation
for consumers and businesses. These criteria are:
1. Inherent vulnerability to fishing pressure
2. Status of wild stocks
3. Nature and extent of discarded bycatch
4. Effect of fishing practices on habitats and ecosystems
5. Effectiveness of the management regime
Each criterion includes:
• Primary factors to evaluate and rank
• Secondary factors to evaluate and rank
• Evaluation guidelines2 to synthesize these factors
• A resulting rank for that criterion
Once a rank has been assigned to each criterion, an overall seafood recommendation for the
species in question is developed based on additional evaluation guidelines. The ranks for each
criterion, and the resulting overall seafood recommendation, are summarized in a table. Criterion
1
“Fish” is used throughout this document to refer to finfish, shellfish and other wild-caught invertebrates.
Evaluation Guidelines throughout this document reflect common combinations of primary and secondary
factors that result in a given level of conservation concern. Not all possible combinations are shown –
other combinations should be matched as closely as possible to the existing guidelines.
2
43
ranks and the overall seafood recommendation are color-coded to correspond to the categories of
the Seafood Watch pocket guide:
Best Choices/Green: Consumers are strongly encouraged to purchase seafood in this category.
The wild-caught species is sustainable as defined by Seafood Watch.
Good Alternatives/Yellow: Consumers are encouraged to purchase seafood in this category, as
they are better choices than seafood in the Avoid category. However there are some concerns
with how this species is fished and thus it does not demonstrate all of the qualities of a sustainable
fishery as defined by Seafood Watch.
Avoid/Red: Consumers are encouraged to avoid seafood in this category, at least for now.
Species in this category do not demonstrate enough qualities to be defined as sustainable by
Seafood Watch.
44
CRITERION 1: INHERENT VULNERABILITY TO FISHING PRESSURE
Guiding Principle: Sustainable wild-caught species have a low vulnerability to fishing pressure,
and hence a low probability of being overfished, because of their inherent life history
characteristics.
Primary Factors3 to evaluate
Intrinsic rate of increase (‘r’)
¾ High (> 0.16)
¾ Medium (0.05 - 0.16)
¾ Low (< 0.05)
¾ Unavailable/Unknown
Age at 1st maturity
¾ Low (< 5 years)
¾ Medium (5 - 10 years)
¾ High (> 10 years)
¾ Unavailable/Unknown
Von Bertalanffy growth coefficient (‘k’)
¾ High (> 0.16)
¾ Medium (0.05 - 0.15)
¾ Low (< 0.05)
¾ Unavailable/Unknown
Maximum age
¾ Low (< 11 years)
¾ Medium (11 - 30 years)
¾ High (> 30 years)
¾ Unavailable/Unknown
3
These primary factors and evaluation guidelines follow the recommendations of Musick et al. (2000).
Marine, estuarine, and diadromous fish stocks at risk of extinction in North America (exclusive of Pacific
salmonids). Fisheries 25:6-30.
45
Reproductive potential (fecundity)
¾ High (> 100 inds./year)
¾ Moderate (10 – 100 inds./year)
¾ Low (< 10 inds./year)
¾ Unavailable/Unknown
Secondary Factors to evaluate
Species range
¾ Broad (e.g. species exists in multiple ocean basins, has multiple intermixing stocks
or is highly migratory)
¾ Limited (e.g. species exists in one ocean basin)
¾ Narrow (e.g. endemism or numerous evolutionary significant units or restricted to
one coastline)
Special Behaviors or Requirements: Existence of special behaviors that increase ease or
population consequences of capture (e.g. migratory bottlenecks, spawning aggregations, site
fidelity, unusual attraction to gear, sequential hermaphrodites, segregation by sex, etc., OR
specific and limited habitat requirements within the species’ range).
¾ No known behaviors or requirements OR behaviors that decrease vulnerability
(e.g. widely dispersed during spawning)
¾ Some (i.e. 1 - 2) behaviors or requirements
¾ Many (i.e. > 2) behaviors or requirements
Quality of Habitat: Degradation from non-fishery impacts
¾ Habitat is robust
¾ Habitat has been moderately altered by non-fishery impacts
¾ Habitat has been substantially compromised from non-fishery impacts and thus has
reduced capacity to support this species (e.g. from dams, pollution, or
coastal development)
46
Evaluation Guidelines
1) Primary Factors
a) If ‘r’ is known, use it as the basis for the rank of the Primary Factors.
b) If ‘r’ is unknown, then the rank from the remaining Primary Factors (in order of
importance, as listed) is the basis for the rank.
2) Secondary Factors
a) If a majority (2 out of 3) of the Secondary Factors rank as Red, reclassify the
species into the next lower rank (i.e. Green becomes Yellow, Yellow becomes
Red). No other combination of Secondary Factors can modify the rank from the
Primary Factors.
b) No combination of primary and secondary factors can result in a Critical
Conservation Concern for this criterion.
Conservation Concern: Inherent Vulnerability
¾ Low (Inherently Resilient)
¾ Moderate (Moderately Vulnerable)
¾ High (Highly Vulnerable)
47
CRITERION 2: STATUS OF WILD STOCKS
Guiding Principle: Sustainable wild-caught species have stock structure and abundance
sufficient to maintain or enhance long-term fishery productivity.
Primary Factors to evaluate
Management classification status
¾ Underutilized OR close to virgin biomass
¾ Fully fished OR recovering from overfished OR unknown
¾ Recruitment or growth overfished, overexploited, depleted or “threatened”
Current population abundance relative to BMSY
¾ At or above BMSY (> 100%)
¾ Moderately Below BMSY (50 – 100%) OR unknown
¾ Substantially below BMSY (< 50%)
Occurrence of overfishing (current level of fishing mortality relative to overfishing threshold)
¾ Overfishing not occurring (Fcurr/Fmsy < 1.0)
¾ Overfishing is likely/probable OR fishing effort is increasing with poor
understanding of stock status OR Unknown
¾ Overfishing occurring (Fcurr/Fmsy > 1.0)
Overall degree of uncertainty in status of stock
¾ Low (i.e. current stock assessment and other fishery-independent data are
robust OR reliable long-term fishery-dependent data available)
¾ Medium (i.e. only limited, fishery-dependent data on stock status are available)
¾ High (i.e. little or no current fishery-dependent or independent information on stock
status OR models/estimates broadly disputed or otherwise out-of-date)
Long-term trend (relative to species’ generation time) in population abundance as measured by
either fishery-independent (stock assessment) or fishery-dependent (standardized CPUE)
measures
¾ Trend is up
¾ Trend is flat or variable (among areas, over time or among methods) OR
Unknown
¾ Trend is down
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Short-term trend in population abundance as measured by either fishery-independent (stock
assessment) or fishery-dependent (standardized CPUE) measures
¾ Trend is up
¾ Trend is flat or variable (among areas, over time or among methods) OR
Unknown
¾ Trend is down
Current age, size or sex distribution of the stock relative to natural condition
¾ Distribution(s) is(are) functionally normal
¾ Distribution(s) unknown
¾ Distribution(s) is(are) skewed
Evaluation Guidelines
A “Healthy” Stock:
1) Is underutilized (near virgin biomass)
2) Has a biomass at or above BMSY AND overfishing is not occurring AND distribution
parameters are functionally normal AND stock uncertainty is not high
A “Moderate” Stock:
1) Has a biomass at 50-100% of BMSY AND overfishing is not occurring
2) Is recovering from overfishing AND short-term trend in abundance is up AND
overfishing not occurring AND stock uncertainty is low
3) Has an Unknown status because the majority of primary factors are unknown.
A “Poor” Stock:
1) Is fully fished AND trend in abundance is down AND distribution parameters are skewed
2) Is overfished, overexploited or depleted AND trends in abundance and CPUE are up.
3) Overfishing is occurring AND stock is not currently overfished.
A stock is considered a Critical Conservation Concern and the species is ranked “Avoid”,
regardless of other criteria, if it is:
1) Overfished, overexploited or depleted AND trend in abundance is flat or down
2) Overfished AND overfishing is occurring
3) Listed as a “threatened species” or similar proxy by national or international bodies
Conservation Concern: Status of Stocks
¾ Low (Stock Healthy)
¾ Moderate (Stock Moderate or Unknown)
¾ High (Stock Poor)
¾ Stock Critical
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CRITERION 3: NATURE AND EXTENT OF DISCARDED BYCATCH4
Guiding Principle: A sustainable wild-caught species is captured using techniques that minimize
the catch of unwanted and/or unmarketable species.
Primary Factors to evaluate
Quantity of bycatch, including any species of “special concern” (i.e. those identified as
“endangered”, “threatened” or “protected” under state, federal or international law)
¾ Quantity of bycatch is low (< 10% of targeted landings on a per number basis) AND
does not regularly include species of special concern
¾ Quantity of bycatch is moderate (10 – 100% of targeted landings on a per number basis)
AND does not regularly include species of special concern OR Unknown
¾ Quantity of bycatch is high (> 100% of targeted landings on a per number basis) OR
bycatch regularly includes threatened, endangered or protected species
Population consequences of bycatch
¾ Low: Evidence indicates quantity of bycatch has little or no impact on population
levels
¾ Moderate: Conflicting evidence of population consequences of bycatch OR
Unknown
¾ Severe: Evidence indicates quantity of bycatch is a contributing factor in driving one
or more bycatch species toward extinction OR is a contributing factor in limiting the
recovery of a species of “special concern”
Trend in bycatch interaction rates (adjusting for changes in abundance of bycatch species) as a
result of management measures (including fishing seasons, protected areas and gear
innovations):
¾ Trend in bycatch interaction rates is down
¾ Trend in bycatch interaction rates is flat OR Unknown
¾ Trend in bycatch interaction rates is up
¾ Not applicable because quantity of bycatch is low
4
Bycatch is defined as species that are caught but subsequently discarded because they are of undesirable
size, sex or species composition. Unobserved fishing mortality associated with fishing gear (e.g. animals
passing through nets, breaking free of hooks or lines, ghost fishing, illegal harvest and under or
misreporting) is also considered bycatch. Bycatch does not include incidental catch (non-targeted catch) if
it is utilized, is accounted for, and is managed in some way.
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Secondary Factor to evaluate
Evidence that the ecosystem has been or likely will be substantially altered (relative to natural
variability) in response to the continued discard of the bycatch species
¾ Studies show no evidence of ecosystem impacts
¾ Conflicting evidence of ecosystem impacts OR Unknown
¾ Studies show evidence of substantial ecosystem impacts
Evaluation Guidelines
Bycatch is “Minimal” if:
1) Quantity of bycatch is <10% of targeted landings AND bycatch has little or no impact on
population levels.
Bycatch is “Moderate” if:
1) Quantity of bycatch is 10 - 100% of targeted landings
2) Bycatch regularly includes species of “special concern” AND bycatch has little or no
impact on the bycatch population levels AND the trend in bycatch interaction rates is not
up.
Bycatch is “Severe” if:
1) Quantity of bycatch is > 100% of targeted landings
2) Bycatch regularly includes species of “special concern” AND evidence indicates bycatch
rate is a contributing factor toward extinction or limiting recovery AND trend in bycatch
is down.
Bycatch is considered a Critical Conservation Concern and the species is ranked “Avoid”,
regardless of other criteria, if:
1) Bycatch regularly includes species of special concern AND evidence indicates bycatch
rate is a factor contributing to extinction or limiting recovery AND trend in bycatch
interaction rates is not down.
2) Quantity of bycatch is high AND studies show evidence of substantial ecosystem
impacts.
Conservation Concern: Nature and Extent of Discarded Bycatch
¾ Low (Bycatch Minimal)
¾ Moderate (Bycatch Moderate)
¾ High (Bycatch Severe)
¾ Bycatch Critical
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CRITERION 4: EFFECT OF FISHING PRACTICES ON HABITATS AND
ECOSYSTEMS
Guiding Principle: Capture of a sustainable wild-caught species maintains natural functional
relationships among species in the ecosystem, conserves the diversity and productivity of the
surrounding ecosystem, and does not result in irreversible ecosystem state changes.
Primary Habitat Factors to evaluate
Known (or inferred from other studies) effect of fishing gear on physical and biogenic habitats
¾ Minimal damage (i.e. pelagic longline, midwater gillnet, midwater trawl, purse
seine, hook and line, or spear/harpoon)
¾ Moderate damage (i.e. bottom gillnet, bottom longline or some pots/ traps)
¾ Great damage (i.e. bottom trawl or dredge)
For specific fishery being evaluated, resilience of physical and biogenic habitats to disturbance
by fishing method
¾ High (e.g. shallow water, sandy habitats)
¾ Moderate (e.g. shallow or deep water mud bottoms, or deep water sandy habitats)
¾ Low (e.g. shallow or deep water corals, shallow or deep water rocky bottoms)
¾ Not applicable because gear damage is minimal
If gear impacts are moderate or great, spatial scale of the impact
¾ Small scale (e.g. small, artisanal fishery or sensitive habitats are strongly
protected)
¾ Moderate scale (e.g. modern fishery but of limited geographic scope)
¾ Large scale (e.g. industrialized fishery over large geographic areas)
¾ Not applicable because gear damage is minimal
Primary Ecosystem Factors to evaluate
Evidence that the removal of the targeted species or the removal/deployment of baitfish has or
will likely substantially disrupt the food web
¾ The fishery and its ecosystem have been thoroughly studied, and studies show no
evidence of substantial ecosystem impacts
¾ Conflicting evidence of ecosystem impacts OR Unknown
¾ Ecosystem impacts of targeted species removal demonstrated
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Evidence that the fishing method has caused or is likely to cause substantial ecosystem state
changes, including alternate stable states
¾ The fishery and its ecosystem have been thoroughly studied, and studies show no
evidence of substantial ecosystem impacts
¾ Conflicting evidence of ecosystem impacts OR Unknown
¾ Ecosystem impacts from fishing method demonstrated
Evaluation Guidelines
The effect of fishing practices is “Benign” if:
1) Damage from gear is minimal AND resilience to disturbance is high AND neither
Ecosystem Factor is red.
The effect of fishing practices is “Moderate” if:
1) Gear effects are moderate AND resilience to disturbance is moderate or high AND
neither Ecosystem Factor is red.
2) Gear results in great damage AND resilience to disturbance is high OR impacts are small
scale AND neither Ecosystem Factor is red.
3) Damage from gear is minimal and one Ecosystem factor is red.
The effect of fishing practices is “Severe” if:
1) Gear results in great damage AND the resilience of physical and biogenic habitats to
disturbance is moderate or low.
2) Both Ecosystem Factors are red.
Habitat effects are considered a Critical Conservation Concern and a species receives a
recommendation of “Avoid”, regardless of other criteria if:
¾ Four or more of the Habitat and Ecosystem factors rank red.
Conservation Concern: Effect of Fishing Practices on Habitats and Ecosystems
¾ Low (Fishing Effects Benign)
¾ Moderate (Fishing Effects Moderate)
¾ High (Fishing Effects Severe)
¾ Critical Fishing Effects
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CRITERION 5: EFFECTIVENESS OF THE MANAGEMENT REGIME
Guiding Principle: The management regime of a sustainable wild-caught species implements and
enforces all local, national and international laws and utilizes a precautionary approach to ensure
the long-term productivity of the resource and integrity of the ecosystem.
Primary Factors to evaluate
Stock Status: Management process utilizes an independent scientific stock assessment that seeks
knowledge related to the status of the stock
¾ Stock assessment complete and robust
¾ Stock assessment is planned or underway but is incomplete OR stock assessment
complete but out-of-date or otherwise uncertain
¾ No stock assessment available now and none is planned in the near future
Scientific Monitoring: Management process involves regular collection and analysis of data
with respect to the short and long-term abundance of the stock
¾ Regular collection and assessment of both fishery-dependent and
independent data
¾ Regular collection of fishery-dependent data only
¾ No regular collection or analysis of data
Scientific Advice: Management has a well-known track record of consistently setting or
exceeding catch quotas beyond those recommended by its scientific advisors and other
external scientists:
¾ No
¾ Yes
¾ Not enough information available to evaluate OR not applicable because little or
no scientific information is collected
Bycatch: Management implements an effective bycatch reduction plan
¾ Bycatch plan in place and reaching its conservation goals (deemed effective)
¾ Bycatch plan in place but effectiveness is not yet demonstrated or is under debate
¾ No bycatch plan implemented or bycatch plan implemented but not meeting its
conservation goals (deemed ineffective)
¾ Not applicable because bycatch is “low”
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Fishing practices: Management addresses the effect of the fishing method(s) on habitats and
ecosystems
¾ Mitigative measures in place and deemed effective
¾ Mitigative measures in place but effectiveness is not yet demonstrated or is
under debate
¾ No mitigative measures in place or measures in place but deemed ineffective
¾ Not applicable because fishing method is moderate or benign
Enforcement: Management and appropriate government bodies enforce fishery regulations
¾ Regulations regularly enforced by independent bodies, including logbook reports,
observer coverage, dockside monitoring and similar measures
¾ Regulations enforced by fishing industry or by voluntary/honor system
¾ Regulations not regularly and consistently enforced
Management Track Record: Conservation measures enacted by management have resulted in
the long-term maintenance of stock abundance and ecosystem integrity
¾ Management has maintained stock productivity over time OR has fully recovered the
stock from an overfished condition
¾ Stock productivity has varied and management has responded quickly OR stock has
not varied but management has not been in place long enough to evaluate its
effectiveness OR Unknown
¾ Measures have not maintained stock productivity OR were implemented only after
significant declines and stock has not yet fully recovered
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Evaluation Guidelines
Management is deemed to be “Highly Effective” if the majority of management factors are green
AND the remaining factors are not red.
Management is deemed to be “Moderately Effective” if:
1) Management factors “average” to yellow
2) Management factors include one or two red factors
Management is deemed to be “Ineffective” if three individual management factors are red,
including especially those for Stock Status and Bycatch.
Management is considered a Critical Conservation Concern and a species receives a
recommendation of “Avoid”, regardless of other criteria if:
1) There is no management in place
2) The majority of the management factors rank red.
Conservation Concern: Effectiveness of Management
¾ Low (Management Highly Effective)
¾ Moderate (Management Moderately Effective)
¾ High (Management Ineffective)
¾ Critical (Management Critically Ineffective)
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Overall Seafood Recommendation
Overall Guiding Principle: Sustainable wild-caught seafood originates from sources that can
maintain or increase production in the long-term without jeopardizing the structure or function of
affected ecosystems.
Evaluation Guidelines
A species receives a recommendation of “Best Choice” if:
1) It has three or more green criteria and the remaining criteria are not red.
A species receives a recommendation of “Good Alternative” if:
1) Criteria “average” to yellow
2) There are four green criteria and one red criteria
3) Stock Status and Management criteria are both ranked yellow and remaining criteria are
not red.
A species receives a recommendation of “Avoid” if:
1) It has a total of two or more red criteria
2) It has one or more Critical Conservation Concerns.
Summary of Criteria Ranks
Conservation Concern
Sustainability Criteria
Low Moderate High
Critical
Inherently Vulnerability
Status of Wild Stocks
Nature and Extent of Discarded Bycatch
Habitat and Ecosystem Effects
Effectiveness of Management
Overall Seafood Recommendation
Best Choice
Good Alternative
Avoid
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