How DFO Science Uses
At-Sea Observer Data
Background
n
Observer Program was established in 1977 to monitor fishing activity of Foreign
and Domestic fishing fleets operating in CDN waters; not actually a Science
Program, administered by C&P and Fisheries Management with Science input
on data collection
n
At-sea observers are deployed on commercial fishing vessels to collect data on
kept/discarded catch by species; gather information on fish size composition
and morphology, fishing location, vessel and gear features and other
information; this data is validated, edited and uploaded to a relational (Oracle)
database
n
Provides the main source of information available on harvested species that are
not retained from commercial fishing operations to comply with management
regulations (i.e. licence restrictions, size limits) or are discarded illegally through
high-grading; also report on catches of non-harvested or prohibited species
which are typically discarded at sea
n
Although retained catches can be monitored effectively through dockside
monitoring programs, the only reliable means of estimating discards is through
direct observation of fishing activities by at-sea observers or electronic
monitoring systems
Background cont’d…….
n
At-sea observers have several functions: provide details on the type of
fishing gear used, fishing location, estimates of the weight of all kept and
discarded species from each set, also collect individual length/weight
measurements by species, biological data (i.e. maturity stages, moult
condition, hard parts for ageing) and conduct tagging work (sea turtles)
n
Observer coverage can vary by fishery, gear type and year; i.e. ~ 2% for 4X
groundfish LL, 5-10% for pelagic LL and 60% for 5Z groundfish mobile gear
sector
n
Lower levels of observer coverage result in higher levels of error in bycatch
estimation
n
Literature suggests that coverage of at least 20% is required for estimates of
common bycatch species while >50% coverage would be needed for rare
species (NMFS aims for 20-30% coverage for NE US fisheries)
Background cont’d…….
n
Since not every trip is observed, some form of estimation is required to
prorate discards from observed trips to total discards for the fishery. This
usually involves using some form of ratio estimator, such that:
DISCARDS = LANDINGS * (discards/landings)
DISCARDS - the total estimated discards of species A
LANDINGS - the total landings of all species
discards - the observed discards of species A
landings - the observed landings of all species
n
Could also use number of trips or some measure of effort in these
calculations to prorate to total fishery
DFO Evaluation of Gaps in Observer
Coverage
n
Part of Ecosystem Approach to fisheries is through effective management of
bycatch and discards; this has become increasingly important with the MSC
process and for monitoring species protected under SARA (i.e. wolffish) and
designated at risk by COSEWIC (i.e. winter skate, thorny skate, cusk)
n
In Maritimes Region, one of the first contributions to this process was an
analysis by Gavaris et al. (2010) which estimated discards from several
fisheries on the Scotian Shelf and Georges Bank using observer and fishery
data from 2002-2006; main objective was to identify gaps in monitoring and
potential conservation concerns
n
Disclosed that levels of observer coverage at the time for some fisheries
was too low and intermittent to provide reliable discard estimates
n
Recommended improving observer coverage on inshore scallop, inshore
lobster, groundfish LL and pelagic LL fisheries
DFO Evaluation Cont’d
n
Additional resources provided through SARA funding (2008-2011?) to
enhance observer coverage for several of these fisheries
n
Led to work on evaluating discards from inshore scallop fisheries in SFA’s 28
(BoF) and 29 west (SWNS) (2002-2009), Lobster Fishing areas 27-33 (20092010) and various groundfish fisheries in 4X5Yb (2007-2011)
Clark, K.J., Hansen, S.C., and Gale, J. 2015. Overview of Discards from Canadian
Commercial Groundfish Fisheries in Northwest Atlantic Fisheries Organization (NAFO)
Divisions 4X5Yb for 2007-2011. DFO Can. Sci. Advis. Sec. Res. Doc. 2015/054. iv + 51 p.
Pezzack, D.S., Denton, C.M., and Tremblay, M. J. 2014. Overview of By-catch and
Discards in the Maritimes Region Lobster Fishing Areas (LFAs) 27-33 based on Species
at Risk Act (SARA) At-sea Sampling 2009-2010. DFO Can. Sci. Advis. Sec. Res. Doc.
2014/040. v + 27 p.
Sameoto, J.A and Glass, A. 2012. An Overview of Discards from the Canadian Inshore
Scallop Fishery in SFA 28 and SFA 29 West for 2002 to 2009. Can.Tech. Rep. Fish.
Aquat. Sci. 2979:vi+39 p.
Some examples of how at-sea
observer data is used for estimating
bycatch, discard rates,
Science/Industry surveys and at-sea
experiments
Cod, Haddock and Yellowtail Flounder Discards
from the Georges Bank Scallop Fishery
Monthly Discard Rate
Catch rate (kg/hm)
0.40
Yellowtail
Cod
Haddock
0.30
0.20
n
Since 2007, the TRAC assessments of cod,
haddock and yellowtail have included
estimates of discards from the offshore
scallop fishery
n
Goal is to account for additional mortality
from non-directed fishing activity for these
species (not allowed to land groundfish)
n
2 observed scallop trips/month; observers
estimate discarded wt/set and obtain LF’s of
groundfish bycatch
n
Monthly discard amounts are calculated by
multiplying scallop fleet effort (hm) by
observed discard rate (kg/hm); then calculate
discards at size (using LF’s and discard
amounts) and apply ALK’s to generate the
catch at age and weight at age of discards
n
Included in the data inputs for the agestructured population models for cod,
haddock and yellowtail flounder
0.10
0.00
0
1
2
3
4
5
6
7
8
9
10
11
12
Month
10000
Discarded Numbers at Size
9000
Half 1
Half 2
Number of Discards
8000
7000
6000
5000
4000
3000
2000
1000
0
15
20
25
30
35
40
Fork Length (cm)
45
50
55
Sub-trips
Q1
Q2
Q3
Q4
Total
Ratio
cod:had
Q1
Q2
Q3
Q4
M±SE
Zone A
Obs
Unobs
20
23
43
5
14
19
Zone A
Obs
Unobs
NA
0.009
0.022
NA
0.022
0.016
Zone A
Zone B
Obs
Unobs
11
1
33
16
60
6
10
17
Zone B
Obs
Unobs
0.024
0.080
NA
NA
0.044
0.015
0.042
0.022
Q2
NA
NA
Q3
2.48±1.55
4.21±2.76
Q4
1.42 0.58
1.13±0.33
Zone A
Obs
Unobs
Zone B
Obs
Unobs
4.040
0.260
NA
NA
14.204
0.071
2.507
2.712
20.751
3.043
Cod (mt)
Q1
Q2
Q3
Q4
Total
Discards
(mt)
Q1
NA
1.730
4.220
5.950
NA
0.811
2.405
3.216
Zone A
n
As part of the quota monitoring for eastern Georges
Bank cod, a multiplier is calculated based on the
cod:haddock catch ratio from observed trips (ISDB)
vs unobserved trips (MARFIS), then used to multiply
the landings of unobserved trips to calculate the cod
discard estimate
n
Analysis is done by fleet sectors, fishing zones and
quarters which have < 100 % observer coverage
n
Amounts are added into total cod catches used in
the stock assessment for 5Zjm cod and are used to
determine any quota over-runs
Zone B
2.87±0.23
Q1
Cod Discards from
EGB Groundfish
Fishery
Zone B
Assumptions:
¨
Observed trips are representative of fishery
¨
There is appropriate observer coverage of the
fishery in time and space
¨
Fishing occurs in the same manner with or
without observer on board
0.485
Q2
NA
NA
Q3
1.201
0.228
Q4
1.014
0.348
Bycatch Analyses for 4X5Y
Haddock Fisheries
n
During Framework Assessments for groundfish stocks, ToR usually include
providing estimates of bycatch from directed and non-directed fisheries
n
Using 4X5Y Haddock as an example, calculated % bycatch kept and discarded
for Haddock-directed Fisheries (i.e. mobile and fixed gear), and for Haddock
Bycatch Fisheries (i.e. the 4X redfish fishery)
§
Note that annual observer
coverage is highly variable,
averaging 4% for Had MG, 2%
for Had FG % and 5% for RF
MG (2004-2013)
§
Coverage would need to be
higher (~20%) in order to
estimate bycatch rates of
commonly discarded species;
especially for analysis at a finer
scale
16.0
% Observer coverage
14.0
12.0
Haddock MG
Redfish MG
Haddock FG
10.0
8.0
6.0
4.0
2.0
0.0
2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
Percent Kept or Discarded
Kept vs Discarded Bycatch for 2004-2013 from
Haddock-directed Mobile Gear Trips in 4X5Y
60
50
40
Haddock Mobile (2004-2013)
% Kept
% Discarded
30
20
10
0
Observer
Coverage of 4X5Y
Haddock Fishery
n
Even with low levels of observer coverage can get an indication of what the kept
and discarded bycatch is but it may not be enough to provide accurate bycatch
ratio estimators which can be expanded to the total fishery (due to high
variability)
Port vs Observer Sample Size Comparisons of
Haddock captured in the Redfish Fishery
16.0
2011
12.0
Smesh OBS
(n=6755)
10.0
8.0
6.0
4.0
10.0
8.0
6.0
4.0
2.0
2.0
0.0
0.0
20
25
30
35
40
45
50
55
60
65
25
70
Total length (cm)
Smesh PS
(n=1977)
Smesh OBS
(n=2085)
2013
16.0
12.0
4.0
0.0
30
35
40
45
50
55
Total length (cm)
35
40
45
50
55
60
65
70
n
Information on fish size composition
from port (shore) and observer (atsea) sampling can be used to
determine if high-grading or
discarding of small fish may be
occurring
n
This example show comparisons of
haddock size composition from
Redfish fishery, no evidence of
discarding in most years
8.0
25
30
Total length (cm)
20.0
Catch st size (%)
Smesh PS
(n=2686)
Smesh OBS
(n=920)
2012
12.0
Catch st size (%)
Catch st size (%)
14.0
14.0
Smesh PS
(n=1890)
60
65
70
Atlantic Halibut
(3NOPs4VWX5Z)
Assessment
n
Halibut assessment relies on the
observer program to collect data for
the industry/DFO halibut longline
survey used as a biomass index for
the assessment model
n
In interim assessment years,
halibut longline survey biomass
index is used to provide science
advice on the TAC
n
Observer data from the halibut
fishery is also used to generate
length-compositions for the
assessment model and to assess
catches on non-targeted species
n
Detailed estimates of bycatch were
recently provided in: Themelis and
den Heyer 2015. CSAS Res. Doc.
2015/042
n
White hake, cusk, cod and
barndoor skates represented much
of the bycatch
Pelagic Longline CPUE
and Bycatch Estimates
Figure - Standardized index of abundance
for bluefin tuna in the Northwest Atlantic
from combined Canada and U.S. pelagic
longline observer data
§
At-sea observers are deployed on 510% of all CDN pelagic longline trips
annually
§
Observer information on BFT bycatch
rates in the pelagic longline fishery is
used in a joint CDN/US index of
abundance for entire east coast
§
Series provides broad geographic
coverage of the fishing area and is
used as a tuning index in the
population model
§
Observer data also used to estimate
dead discards of BFT and SWO for
use in ICCAT stock assessments
§
Observers provide extra biological
sampling, conduct turtle tagging and
collect information on seasonal/spatial
distribution of all species caught
Scallop Fishery
Area/Time Closure to
Reduce Yellowtail
Flounder Bycatch on
Georges Bank
n
Observer data from the groundfish mobile gear
sector on eastern Georges Bank is used to
calculate Yellowtail Flounder bycatch rates
(kg/hr) for the month of June (when bycatch
rates are highest)
n
Data is aggregated to determine areas/cells of
higher yellowtail densities
n
Cells where bycatch rates exceed an
established threshold could qualify for scallop
fishery area/time closure during the month of
June in the following year
n
Final selection of cell closures determined by
industry and fisheries management; goal is to
reduce scallop fishing effort in these areas
Yellowtail
Bycatch
Scallop
Catches
Scotian Shelf Snow Crab Assessment
Snow Crab Survey Set Locations
n
Eastern Scotian Shelf snow crab assessment relies on the
observer program to help collect data for the industry/Science
snow crab survey used as a biomass index in the assessment
model to estimate fishable biomass
n
Routine monitoring of landings (5% coverage) provides data on
commercial catch size composition (legal, sublegal) and shell
hardness (condition)
n
Provide distribution/abundance of soft-shelled crab so that industry
can avoid fishing these areas; maps are created in real time and
distributed to industry
n
Estimates of discarded bycatch (impact of fishery on other species)
Monitoring Lobster Bycatch in SFA29 West
Location and number of
lobsters caught in SFA
29 West in 2013 from
observed scallop
fishing trips
Table 4. Estimated total numbers of lobsters caught in the SFA 29 West scallop
fishery (Full Bay and East of Baccaro combined) for 2011–2013 based upon
observer data. DI (%) refers to the percentage of dead or injured lobsters.
Year
Area
Observer data
No. lobsters
2011
2012
2013
A
B
C
D
E
Total
A
B
C
E
Total
A
B
C
D
E
Total
DI (%)
24
735
1
18
188
966
24
164
104
47
339
13
331
103
50
122
619
46
33
100
61
0
9
49
2
8
24
19
22
24
Fishery
Estimated
Meats (t)
Meats (t)
No. lobsters
DI
0.5
5.4
0.1
6.3
1.1
13.4
0.4
7
2
0.7
10.4
0.002
7.4
2.2
3.2
1.0
13.9
18.1
59.3
45.4
69.8
5.6
198.1
1.0
78.1
39.8
18.0
168.9
1.3
87.5
18.3
38.8
13.5
159.3
867
8,065
454
200
959
10,545
61
1,830
2,069
1,207
5,168
8,436
3,898
846
606
1,598
15,385
398
2,667
0
200
582
3,845
0
163
1,014
26
1,203
649
954
164
133
386
2,286
n
For Scallop Fishing Area 29 West, data from observed trips is used to monitor the direct
effects of the scallop fishery on the lobster stock (i.e. to provide estimates of the number
of live, dead and injured lobsters)
n
Also used to evaluate the discard rates of fish and invertebrate species by the inshore
scallop fleet (a mandatory part of the management of SFA 29 West)
Offshore Lobster (LFA 41)
Sea sampling
locations 20082012
n
At-sea Observers provide main source of sampling of trap catches from the Offshore Lobster
fishery (LFA 41)
n
Data collected on lobster includes carapace length measurements, sex id, egg presence and
stage, shell hardness, occurrence of culls and v-notches, trap numbers, location and depth of
fishing
n
Also provides information on retained and discarded incidental catches (species composition,
estimated weights, length measurements)
n
Used in the stock assessment of LFA 41 lobster as a primary indicator of population size
structure and a secondary indicator of reproductive potential
Mobile Gear Cod End Mesh Size Experiments for EGB Haddock
25
25
Qtr 2
145 dia
20
130 sq
15
10
5
15
10
5
0
10
15
20
25
30
35
40
45
50
55
60
65
70
0
75
10
25
15
20
25
30
35
40
45
50
55
60
65
70
75
25
Qtr 3
145 dia
130 sq
125 sq
20
Qtr 4
145 dia
130 sq
125 sq
20
Frequency (%)
Frequency (%)
145 dia
130 sq
125 sq
20
Frequency (%)
Frequency (%)
Qtr 1
15
10
5
15
10
5
0
10
15
20
25
30
35
40
45
50
Fork length (cm)
55
60
65
70
75
0
10
15
20
25
30
35
40
45
50
55
60
65
70
75
Fork length (cm)
n
In 2014 observers collected length measurements for EGB haddock from bottom trawls
using the standard (130mm sq mesh cod end) and two experimental cod end mesh types
(145mm diamond and 125mm sq mesh)
n
Exceptionally large 2010 yc was slower growing (smaller) than adjacent YC’s, industry
concerned about increased cost and effort to obtain good catches
n
Observers deployed on 64% of MG trips, measured over 470,000 haddock
n
Experimental mesh did not retain more small haddock than standard mesh but had
improved catch rates; also did not exhibit increased bycatch of cod
Summary
n
Incidental bycatch and discarding of non-targeted species occurs in many CDN
fisheries. DFO Science and FM have to establish appropriate levels of observer
coverage, manage discards of all targeted species and control incidental mortality of
non-targeted species - this has become increasingly important with the MSC process
and for monitoring SARA species
n
Observer program used for industry/Science surveys (halibut, Scotian Shelf snow
crab), to provide data for monitoring of kept and discarded species (targeted and
bycatch), to conduct at-sea experiments and special biological sampling
n
Could always use more Observer Coverage; i.e. still low for many fisheries (Pelagic
LL, 4X5Y groundfish, offshore scallop). Video monitoring may be helpful for these
n
NMFS aims for 20-30% coverage for all fisheries in NE region, but US industry
currently does not have to pay for this service
n
Common theme for at-sea observer coverage: measuring target species at sea to
comply with management regulations on minimum size restrictions and special
biological sampling at sea; is it possible to do these tasks with video monitoring??