west atlantic bluefin tuna executive summary. biology continued progress in knowledge of bluefin...
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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
0
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50000
60000
1950 1960 1970 1980 1990 2000
Ca
tch
es
(t)
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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2000
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1970 1980 1990 2000
Ca
tch
es
(t)
Fishery indicators: abundance indices
No consistent changes inCPUE
U.S. East Coast RR
0
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4
1990 1995 2000 2005 2010Year
Rel
ativ
e in
dex
SMSM
LGSM
LGMED-LG
U.S. GOM
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1
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1985 1990 1995 2000 2005 2010Year
Rel
ativ
e in
dex
ADULT GOM
Japan LL
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1970 1975 1980 1985 1990 1995 2000 2005 2010Year
Rel
ativ
e in
dex
JLL West
CANADA
0
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1975 1980 1985 1990 1995 2000 2005 2010Year
Rel
ativ
e in
dex
SW Nova Scotia
Gulf St. Lawrence
GOM: Larval
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1975 1980 1985 1990 1995 2000 2005 2010Year
Rel
ativ
e in
dex
0
100000
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300000
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500000
600000
1960 1970 1980 1990 2000 2010
Rec
ruit
s
2002 SA
2006 Base
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10000
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30000
40000
50000
60000
1970 1980 1990 2000 2010
SS
B
2002 SA
2006 Base
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0.1
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1970 1980 1990 2000 2010
Fis
hin
g m
ort
alit
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
0.0
0.5
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.)