West Atlantic bluefin tuna Executive Summary

  

Biology

Continued progress in knowledge of bluefin biology, but the complex behaviour of this species means that much research still needed

Recent research in reproductive biology, demographic modeling and age determination suggests western bluefin may be less resilient to fishing than previously thought

WG remains concerned about issues of mixing, and in particular, the inability to quantify the kind and extent of mixing for use in assessments

Need to integrate recent and anticipated advances in otolith microconstituent analyses, archival tagging and genetics into assessment and management evaluation processes.

Fishery indicators: catch

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1950 1960 1970 1980 1990 2000

Ca

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MEDAT.WAT.E

QUOTAS

Fishery indicators: catch

2002 landings (3,319 t) highest since 1981Canadian and Japanese landings stable at 500-600 tU.S. did not catch its quota in 2004-2006 with landings of 899, 717 , and 468 t

AT.W

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1970 1980 1990 2000

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Fishery indicators: abundance indices

No consistent changes inCPUE

U.S. East Coast RR

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1990 1995 2000 2005 2010Year

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SMSM

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LGMED-LG

U.S. GOM

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1985 1990 1995 2000 2005 2010Year

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ADULT GOM

Japan LL

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1970 1975 1980 1985 1990 1995 2000 2005 2010Year

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JLL West

CANADA

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1975 1980 1985 1990 1995 2000 2005 2010Year

Rel

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SW Nova Scotia

Gulf St. Lawrence

GOM: Larval

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1975 1980 1985 1990 1995 2000 2005 2010Year

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0

100000

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1960 1970 1980 1990 2000 2010

Rec

ruit

s

2002 SA

2006 Base

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1970 1980 1990 2000 2010

SS

B

2002 SA

2006 Base

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1970 1980 1990 2000 2010

Fis

hin

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y 8+

2002 SA

2006 Base

Consistent with 2002 SA

Less optimistic estimates of 1994 and 1997 year classes

More optimistic view of recent F’s

State of the stock (review)

State of stock: low U.S. catches

• Plausible explanations(1) that availability of fish to the United States fishery was low(2) the overall size of population in the west declined substantially

• Evidence (SCRS/2007/171)(1) Canada and Japan did not have abnormally low catches

CPUE series from Gulf of St. Lawrence at high levels since 2004 CPUE series from GOM do not show consistent decline

(2) some abundance indices suggest decline declining size composition in some areas small changes in F suggested by tag data despite declining catches

• Conclusion(1) No strong evidence to favor either explanation over the other(2) However, the failure of a fishery to take half of its TAC for several

years, and other new evidence reviewed by the committee, heightened concern that the estimate of stock status from the 2006 assessment may be optimistic

Short-term (5-year) projections to cover time until next

assessment assume future recruitment will fluctuate around recent

levels

Outlook

SSB/SSBMSY

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1.0

1.5

2.0

1975 1980 1985 1990 1995 2000 2005Year

0 MT500 MT1,000 MT1,500 MT2,100 MT2,300 MT2,500 MT2,700 MT3,000 MT

Outlook

SSB/SSBMSY

0.0

0.5

1.0

1.5

2.0

2004 2005 2006 2007 2008 2009

Year

0 MT

500 MT

1,000 MT

1,500 MT

2,100 MT

2,300 MT

2,500 MT

2,700 MT

3,000 MTFMSY ~ 2,100 MT

Current (2006) Catch (including discards) 1,929 tShort-term Sustainable Yield ~2,300 tMaximum Sustainable Yield (MSY|R) 3,200 (3,000-3,400)Relative Spawning Stock Biomass B2004/B1975 0.18 B2004/BMSY|R 0.41 (0.29-0.54)Relative Fishing Mortality3

F2004/FMSY|R 1.7 F2004/F0.1 3.1 F2004/Fmax 1.7Management Measures: 2,100 t TAC from 2007 inc. dead disc [Rec. 06-06] 2,700 t TAC from 2003 inc. dead discards [Rec. 02-07] 30 kg (115 cm FL) min. size with 8% tol. [Rec. 98-07] No directed fisheries in Gulf of Mexico [Rec. 98-07]

F2004 is taken to be the geometric mean of the estimates for 2001-2003

BFTW summary table

Effect of current regulations

• Recommendation 06-06 expected to result in rebuilding stock towards convention objective with fishing mortality rates at about the estimated MSY level

• New evidence suggests that current regulations may be insufficient to achieve the objectives (cannot evaluate until next assessment)

• Ability to achieve the convention objectives would be further hampered by future use of accumulated unused quota (large amount involved for WBFT

Management recommendations

• Commission responded positively, making Rec. 06-06, which establishes a quota of 2,100 MT

• However, the Committee is even more concerned about status of west stock than it was a year ago. Further advice provided after the next assessment (2008).

• Evidence accumulating that both productivity of west stock and west bluefin fisheries linked to the east stock. One plausible explanation for failure of west fishery totake TAC in recent years is that it is partly dependent on

east fish, and east fish now less available to the west • Therefore, management actions taken in the eastern

Atlantic and Mediterranean are likely to impact recovery in the west Atlantic (SCRS 2006 Agenda Item 15.6.)