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


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 )


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


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


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


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


• 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.

atlantic bluefin tuna

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