Download - Atlantic bluefin tuna
Atlantic bluefin tuna
• Two management units since 1981
• Complex spatial dynamics with
mixing between both stocks
(investigated by BFT-SG since 2001)
• Spatial extension of the fisheries
• Significant spatial & temporal
variations in the catches. Current
levels doubful, but among the highest
• Current catches of West Stock ~ 5%
those of East stock
ICCAT BFT-SG 2007
East Atlantic & Mediterranenan Stock
The 2006 stock assessment: a brief reminder
BFT-WG has stressed since 2000 strong concern about data quality, for both
total catch and cath-at-size, mostly due to:
Under-reporting of ICCAT members since TAC implementation (1998)
Illegal fishing (under-sized and flag of convenience)
Loss of information in recent years due to caging
The BFT-WG concluded in 2004 that it was no longer defensible to assess the
stock using only methods that assume that the catch-at-size/age is known exactly
(i.e. VPA), until extensive improvements in fisheries statistics are made
For these reasons, besides the update of the VPA, the 2006 stock assessment
mostly investigated various approaches, such as catch curve, year-class curve,
yield-per-recruit analysis, and based its advice on a larger variety of methods
The 2006 stock assessment: a brief reminder
Vessel category Number of VesselsLow estimate /
VesselBest estimate /
Vessel Max estimate / Vessel
PS large 41 200 t/yr 300 t/yr 400 t/yr
PS medium 103 100 t/yr 150 t/yr 200 t/yr
PS multispecies 170 10 t/yr 40 t/yr 60 t/yr
LL large 56 20 t/yr 50 t/yr 70 t/yr
LL medium 25 6 t/yr 30 t/yr 40 t/yr
LL multispecies 352 1 t/yr 3.5 t/yr 8 t/yr
Handline 390 0.5 t/yr 3 t/yr 5 t/yr
Trap 6 7 t/yr 30 t/yr 60 t/yr
Artisanal 564 0.3 t/yr 4.3 t/yr 6 t/yr
Total commercial vessels 1707
Estimated Yield Commercial vessels 22,228 t 43,107 t 60,630 t
Sport & Recreative 10663 0.01 t/yr 0.03 t/yr 0.06 t/yr
Estimated Yield all vessels 22,376 t 43,417 t 61,316 t
Estimation of fishing capacity in the Mediterranean Sea (based on the number of vessels operating in the Mediterranean Sea and their respective catch rates )
The 2006 stock assessment: a brief reminder
Therefore, the Group
concluded that real catches
since 1998 are more likely to
be close to the levels
reported in the mid-1990s,
i.e. ~ 43,000 t in the
Mediterranean and about
50,000 t in the East Atlantic
& Mediterranean 0
10000
20000
30000
40000
50000
60000
70000
1970 1974 1978 1982 1986 1990 1994 1998 2002 2006
Mediterranean
East Atlantic
The 2006 stock assessment: a brief reminder
SSB continues to decline while Fs are increasing rapidly, especially for large fish
VPA
• No trend on small fish
CPUE
ages 2,3,4
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
scal
ed c
atch
rat
e
SP BB 2
SP BB 3
SP BB 4
ages 8+, 10+
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
scale
d c
atc
h r
ate
s
SP TRAP
MO TRAP
JPN LL A5&Med
• Recent decline for older fish
The 2006 stock assessment: a brief reminder
Based of that, defined a suite per-recruit analyses that can be considered as long-
term evaluations of alternative minimum size (10, 25 and 30kg) and closure options
in time (June, May-June, etc..) and space (East Atl. vs Med)
Estimated temporal pattern in monthly catches of spawning size and juvenile BFT
in the East Atlantic and Mediterranean
YPR
Mediterranean
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
1 2 3 4 5 6 7 8 9 10 11 12
Month
Perc
enta
ge o
f Ann
ual C
atch
Juvenile Fish
Spaw ning Size Fish
East Atlantic
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
1 2 3 4 5 6 7 8 9 10 11 12
Month
Perc
enta
ge o
f Ann
ual C
atch
Juvenile Fish
Spaw ning Size Fish
East & Mediterranean
0%
5%
10%
15%
20%
25%
30%
1 2 3 4 5 6 7 8 9 10 11 12
Month
Perc
enta
ge o
f Ann
ual C
atch
Juvenile Fish
Spaw ning SizeFish
The 2006 stock assessment: a brief reminder
0 10 20 30 40
0.0
0.5
1.0
1.5
2.0
2.5
3.0
% change SSB
% c
hang
e YP
R
0 20 40 60 80 100 120
23
456
7
8
9
10
1112
13
14
15
16
1718
192021
22
23
24
25
2627
28
29
30
31
323334
3536
37
38
39
40
4142
43
44
45
46
SBPR SBPR1970 (%)
F/F
max
SPR (%)
1970
Projecting 2004
The 2006 stock assessment: a brief reminder
• TAC regulation until 2006 was not respected and was largely ineffective in
controlling overall catch
Conclusion
• The 2003-2004 fishing mortality rates would lead to F that would be more than 3
times FMax and would drive the SSB to a very low level (~ 6% SPR)
• Fishery and stock collapse in the near future is a possibility given our
estimations of current fishing capacity and fishing mortality rates. Substantial
reductions in F and catch are thus needed (~15,000 tonnes for short-term)
• Among a number of alternative management scenarios, only those with a closure
of the Mediterranean around spawning season together with an increase in
minimum size can lead to a recovery of the stock
The 2006 recovery plan
A minimum size being extended to 30 kg (with a tolerance of 8 %) and the exception of
BB and TRW in the East Atlantic and catches for farming purposes in the Adriatic Sea for which
the minimum size is set at 8kg
Multiple elements related to monitoring, control and surveillance associated
measures to the TAC
A TAC of 29,500; 28,500; 27,500
and 25,500 tonnes/year for 2007,
2008, 2009 and 2010
An extended closed fishing
season: (i) from the 01 June to 31
December for large LL, (ii) from the 01
July to 31 December for PS and (iii) from
15 November to 15 May for BB & TRW
The 2007 BFT-SG
Investigation of the effects of this recovery plan on stock status
0 10 20 30 40
0.0
0.5
1.0
1.5
2.0
2.5
3.0
% change SSB
% c
hang
e Y
PR
0 20 40 60 80 100 120
23
456
7
8
9
10
1112
13
14
15
16
1718
192021
22
23
24
25
2627
28
29
30
31
323334
3536
37
38
39
40
4142
43
44
45
46
SBPR SBPR1970 (%)
F/F
max
SPR (%)
1. Through the interpolations of the yield-per-recruit outcomes
The 2007 BFT-SG
Investigation of the effects of this recovery plan on stock status
2. Through simulation models
Overall, preliminary results indicate that the current measures are unlikely to
fulfill the objective of the rebuilding plan with 50% probability
• If implementation is perfect and future recruitment at ~1990s level, there is about 50%
probability of rebuilding by 2023 under the current regulations
• However, perfect implementation is unlikely, even with perfect enforcement, because
avoiding totally discard mortality of small fish and reducing fishing effort to very low levels
does not appear to be feasible
• With other plausible assumptions (imperfect implementation and/or lower or declining
recruitment) the objectives of the rebuilding plan will not be met.