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9
ICES WGHANSA REPORT 2014
Blue Jack Mackerel ( Trachurus picturatus ) in the waters of
Azores
The T. picturatus is the only species of genus Trachurus that occurs in the Azores region (northeastern Atlantic). It is a pelagic species found around the islands shelves,
banks and seamounts up to 300 m depth. However, a different size structure was
observed between islands shelf and offshore areas. The island shelf areas seems to
function as nursery or growth zones, while the seamount/bank offshore areas as feeding zones where adults predominate (Menezes et al., 2006).
In the Azores, the T. picturatus is exploited by different fleets and métiers. The main
catches are those of the artisanal fleet that operates with several types of surface nets,
the most important being the purse-seines, and bottom longline.Purse-seines are also
used by the tuna bait boat fleet, which targets the T. picturatus to be used as live bait
for tuna. The blue mackerel is also a very popular species among the recreational
fisherman that fish along the coast of all islands.
The T. picturatus landings were considerably high during the 1980’s, however changes in the local markets lead to a strong reduction in the catches afterwards. This reduction was also accompanied by a sharp decrease in the fleet targeting small pelagic
fish. Since this period, the catches maintained at a low level due to a voluntary auto
regulation adopted by the fishermen associations. Despite this reduction in the landings, this fishery still has a strong impact on some fishermen communities, which
directly depends on the income of this fishery.
9.1
General Blue Jack Mackerel in ICES areas
The blue mackerel, Trachurus picturatus Bowdich, 1825 (Carangidae) has a broad geographical distribution within the Eastern Atlantic waters and can be found from the
southern Bay of Biscay to southern Morocco, including the Macaronesian archipelagos, Tristan de Cunha and Gough Islands and also in the western part of the Mediterranean Sea and the Black Sea (Smith-Vaniz, 1986). It is a pelagic fish species which
characteristic habitat includes the neritic zones of islands shelves, banks and seamounts (Smith-Vaniz, 1986). It has a schooling behaviour and prey mainly on crustaceans, being common in the islands of Madeira, Azores, and Canaries and Portuguese
continental waters.
No studies specifically addressing the existence of distinct populations in the distribution range of this species have been attempted so far. Some studies on growth and
biological characteristics from Madeira, Azores and Canary islands (Isidro, 1990; Jesus, 1992; Gouveia, 1993; Vasconcelos et al., 2006; Jurado-Ruzafa and Santamaría,
2012) indicated similar growth rates and reproductive season. However, biological
differences on age at first maturity seem to exist between individuals from the Azores
compared with those from the Madeira and Canary islands (Jesus, 1992; JuradoRuzafa and Santamaría, 2012). The morphometric studies carried out on T. picturatus
from Azores archipelago (Isidro, 1990), western coast of Portugal (Mendes et al., 2004)
and western Mediterranean (Merella et al., 1997) revealed similar population parameters for the estimated relationships. On the contrary, some variation was found between different geographic areas in the number of soft spines from the second dorsal
fin (Shaboneyev and Kotlyar 1979; Smith-Vaniz, 1986). However, meristic characters
are heavily influenced by the environmental conditions experienced by the fish while
ICES WGHANSA REPORT 2014
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in the larval stages, therefore in the case of migratory oceanic species, such as T. picturatus, are usually considered of reduced utility for the identification of stock units.
A number of studies have successfully used parasites as biological markers.
Gaevskaya and Kovaleva (1985) conducted a survey of the parasites of T. picturatus
from the Azores and Western Sahara. Their study identified a number of protozoan
and helminth parasites showing differences in prevalence. The myxosporean Kudoa
nova was found in samples from the Western Sahara, but not from banks of the
Azores archipelago. Similarly, some species of digeneans (Platyhelminths: Digenea)
found in the banks of the Azores, were not observed in the samples from the Western
Sahara and vice-versa. The apicomplexan, Goussia cruciata which is common in T.
picturatus from the Mediterranean (Kalfa-Papaioannou and AthanassopoulouRaptopoulou, 1984) and more recently from Madeira waters (Gonçalves, 1996), was
not found in the Azores or from the Western Sahara. These variations in the occurrence of parasites could be indicative of the existence of different populations of T.
picturatus. Further studies concentrating the occurrence of helminth parasites indicate
some differences in both species diversity and parasitic infections levels (Costa et al.
2000, 2003).
The blue mackerel is an economically important resource, especially in the Macaronesian islands of Azores and Madeira, where is the main pelagic fish species being
caught in the local fisheries. The landings of this species in the Portuguese mainland
have suffered strong fluctuations, which may be related, at least partially to fluctuations in abundance or availability. From 2005 to 2007 the landings have tripled, being
2007 the year with the highest landings recorded. In the Azores archipelago the landings have also fluctuated, while in Madeira the average of the landings from 1986 to
1991 was three times higher than the average landings from 1992 to 2007. The hypothesis that the fluctuations in landings can be due to changes in availability or
abundance, and not just by changes in fishing effort, is supported for the Portuguese
mainland by the observation of fluctuations in the abundance indices obtained from
research surveys.
9.2
ACOM Advice Applicable to 2014
The advice for this stock is biennial and so the 2012 advice is valid for 2013 and 2014
(see ICES, 2012): ICES advises on the basis of the approach for data limited stocks that
catches should be no more than 1800 tonnes.
9.3
The fishery in 2013
Commercial catches for 2013 include landings, discards (estimated for 2013), tuna bait
catches and recreational catches. For 2013, the discards observer programme didnot
occur due to financial constraints, and so the longline discards (including bait consumption by this fleet) were estimated taking into account the results from the previous years.
In 2013, length frequencies and ages from landings sampling were collected and
commercial abundance indices from the main fleets catching juveniles were also taking into account (LPUE_Purse-seiners and cpue_BaitBoat).
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9.3.1
Fishing Fleets in 2013
The blue mackerel is mostly landed by the artisanal fleet, using purse-seines. This
fleet landings represents around 90% of the total landings and the catches about 60%
of the total catches of blue mackerel, in Azores.
The artisanal purse-seines fleet is composed by small open deck vessels, mostly with
less than 12 meters of length overall. The composition of this fleet has remained quite
stable in the recent years, with 120 vessels registered last year. The contribution of
this fleet to the landings and the number of vessels of each size category, for the last
12 years is showed in Error! Reference source not found..1.
100
180
160
80
120
60
100
%
Number of vessels
140
80
40
60
40
20
20
VL0010
VL1012
VL1218
2013
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
0
0
% of total Landings
Figure 9.3.1.1 Contribution of purse-seine fleet to the landings of blue mackerel in Azores, between 2002 and 2013, and the number of vessels of each size category.
9.3.2
Catches
Commercial catches including landings, discards (estimated for 2013), tuna bait
catches and recreational catches, for the period 1978 to 2013, are presented in Error!
Reference source not found..
Total estimated catches of blue mackerel in the Azores, for the considered period in
Error! Reference source not found..1 (2002-2013), are around 1650 tonnes; while
landings, in same period,are in average 1100 tonnes. In the last three years, the average catches and landings decreased to about 1330 and 750 tonnes, respectively.
Table 9.3.2.1 – Estimated catches of blue jack mackerel (T. picturatus) by fishery, in the Azores
from 1978 to 2013.
Tuna
Discards/Bait
Discards
(PS)
PS
LL+Hand
Total
129
15
0
2657
78
2995
118
130
15
0
4114
61
4439
1980
210
132
22
0
2920
70
3354
1981
229
135
9
0
2104
39
2516
bait
Recreational
1978
115
1979
Year
(LL)
ICES WGHANSA REPORT 2014
Tuna
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Discards/Bait
Discards
(PS)
PS
LL+Hand
Total
142
10
0
2429
43
2862
231
142
21
0
3711
67
4172
1984
295
135
17
0
3180
62
3689
1985
303
136
11
0
3442
60
3952
1986
433
135
9
0
3282
58
3918
1987
491
139
8
0
2974
53
3666
1988
586
143
8
0
3032
55
3824
1989
352
138
9
0
2824
50
3373
1990
345
117
11
27
2472
48
3021
1991
242
115
6
127
1247
33
1770
1992
249
121
6
126
1226
35
1762
1993
375
130
22
173
1684
70
2454
1994
264
125
18
179
1745
59
2390
1995
474
119
24
182
1769
79
2648
1996
351
110
38
173
1642
123
2437
1997
259
110
31
192
1849
72
2513
1998
308
111
52
151
1387
120
2129
1999
141
119
37
35
609
84
1024
2000
83
117
23
32
602
53
910
2001
59
121
24
110
1046
55
1415
2002
82
132
28
145
1387
63
1837
2003
140
128
21
150
1455
47
1941
2004
208
111
19
125
1148
98
1709
2005
124
120
236
123
1111
120
1834
2006
264
111
40
124
1145
96
1781
2007
370
115
58
115
1032
122
1812
2008
205
110
75
111
980
139
1620
2009
230
119
115
112
1023
98
1697
2010
313
114
75
116
1021
57
1696
2011
510
118
79
105
920
62
1794
2012
399
42
41
Not
available
467
94
1043
2013
237
147
54
Not
available
592
123
1153
bait
Recreational
1982
239
1983
Year
(LL)
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ICES WGHANSA REPORT 2014
2500
Catch (ton)
2000
1500
1000
500
PS
Discards (PS)
LL+Hand
Discards/Bait (LL)
Tuna bait
2013
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
0
Recreational
Figure 9.3.2.1 Estimated catches of blue mackerel (T. picturatus) in the Azores (ICES Subdivision
Xa2) from 2002 to 2013.
An important reduction was observed in the catches of all fishing gears in 2012, but
particularly for those targeting the juveniles, such as the artisanal purse-seine fleet
and the tuna baitboats fleet. In the case of the artisanal seiners the reduction observed
was close to 50%. The cause of this reduction is unknown. Concerning the longliners,
the reduction observed in 2012 is mostly related to the practice of using the blue
mackerel for bait, since their market price is too low.These values increased in 2013,
although still are below the average of the preceding 10 years to 2012.
9.3.3
Effort and catch per unit of effort
The fishing effort in number of days at sea is presented by year and by vessel size
category in Error! Reference source not found..1.The majority of the effort is conducted by the small segment of the fleet (VL0010 – vessel with less than 10m), followed by the fleet segment VL1012 (vessels between 10 and 12 metres).
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6000
Effort (days)
5000
4000
3000
2000
1000
0
2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
VL0010
VL1012
VL1218
Total
Figure 9.3.1.1 Nominal effort (number of days) of the purse-seine fleet, total and by vessel size
category for the period 2002-2013.
For the last twelve years, and with the reduction of this fleet in the 90’s, the threshold
of 5000 fishing days has never been exceeded.
The standardized cpue/LPUE series were updated for the small purse-seine fleet
(Error! Reference source not found.Error! Reference source not found.) and the tuna
baitboat fleet (Error! Reference source not found.) of blue jack mackerel, up to 2013.
Landings of blue jack mackerel from the longliners are less representative once a considerable part of the catch is not landed being either discarded or used as bait. The
source of data for updating CPUE series from this fleet is through the discards observer sampling programme but, since it wasnot possible to conduct it in 2013, the
CPUE series for the longliners was not updated.
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ICES WGHANSA REPORT 2014
600
Kg/day fishing
500
400
300
200
100
0
1980
1983
1986
1989
1992
1995
Observed LPUE
1998
2001
2004
2007
2010
2013
Stnd LPUE
Figure 9.3.3.2 Standardized and observed LPUE for blue jack mackerel from the Azores small
purse-seine fishery, for the years 1980-2013. Broken lines indicate 95% confidence intervals.
450
400
Kg/day fishing
350
300
250
200
150
100
50
0
1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
Stnd CPUE
Observed CPUE
Figure 9.3.3.3 Standardized and. observed CPUE for blue jack mackerel from the Azorean baitboat
tuna fishery, for the years 1998-2013. Broken lines indicate 95% confidence intervals.
9.3.4
Catches by length
Size frequencies for the jack mackerel caught in the Azores are available since 1980. In
Error! Reference source not found., is presented the size distribution of the landings
(catch at size) for the years 2002 to 2013. The two main fisheries target on different
size categories, the surface fleets catches the juvenile fraction of the population while
the longliners target the adult stock.
ICES WGHANSA REPORT 2014
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16000000
CAS (Numbers of fish)
14000000
12000000
10000000
8000000
6000000
4000000
2000000
0
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54
cm
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
Figure 9.3.4.1 Annual size frequencies of the catches of blue mackerel (T. picturatus) in the
Azores, from 2002 to 2013.
Assessment of the state of the stock
The assessment method is described in the stock annex.
9.4
Management considerations
The Regional Administration intends, during the current year, put in place a specific
management measure for the purse-seine fleet with the aim of regulate markets. This
measure allows only 200kg per vessel, per day: Also states that fishing and consequent landings shall also be forbidden on weekends.