P1251328622TlYdW

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2007 ICCAT SCRS Executive Summay for Atlantic
Bigeye Tuna
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Biology Distribution 50N-45S, not in
Mediterranean Swimming Behavior extensive
vertical movement, deeper during daytime,
shallower at night. Spawning
tropical-subtropical, mature at age 3 Nursery
Gulf of Guinea Prey fish, mollusk,
crustacean Growth (relatively fast) Age 3
(105 cm), Age 5 (140cm), Age 7 (163cm)
Schooling behavior Juveniles are mixed with
yellowfin and skipjack Natural mortality
estimated by tagging data Stock structure
Atlantic wide
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BETCatch
Fisheries LL(45-50kg), North BB(20-30kg),
PSTrop BB(3-4kg) LL Japan, Chinese Taipei,
China, Philippines PS EC-SpainFrance, Ghana,
Venezuela (in association with FADs)
Figure 1.
Species composition data is important improved
for Ghana
2006 catch is 65,000 t
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BETCatchDistribution
Figure 2.
Geographic distribution of bigeye catches for
most recent years (2002-2005) by major tuna
fishery.
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BET Catch
Unreported catches estimated from trade
statistics.
Figure 3.
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BET abundance Indices
Figure 4-1.
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BETabundance Indices
Figure 4-2.
New CPUE
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BET Abundance Indices
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BET Assessment Models

• Several types of assessment models including
  production models, VPA and a statistical
  integrated model (Multifan-CL) were applied to
  the available data. There was a range of stock
  status evaluations from the various model
  formulations applied, not all of which were
  judged to be equally likely.

Consistent with previous assessments, the results
from nonequilibrium production models are used to
provide our best characterization of the status
of the resource. The current MSY estimated using
two types of production models was about 90,000 t
and 93,000 t, although uncertainty in the
estimates would broaden the range. In addition,
these estimates reflect the current relative
mixture of fisheries that capture small or large
bigeye MSY can change considerably with changes
in the relative fishing effort exerted by surface
and longline fisheries.
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BETModel Results Estimated MSY 90,000
93,000 t
Figure 5.
Trajectories of B-ratio and F-ratio obtained from
ASPIC base case run.
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BETModel Results
MFCL run results. Selectivity curve for each
decade (left). MSY estimates.
1960s
1970s
MSY estimates
1980s
1990s
2000s
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BET Model Results
Figure 6.
Estimated range of stock status results (B/BMSY
and F/FMSY) in 2005 which characterizes our
uncertainty in stock status (right panel). Time
series of B/BMSY and F/FMSY from 1950 to 2005
(left panel).
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BET Outlook
85K
Figure 7.
Stock projections by ASPIC model assuming a catch
of 71,000 t in 2006 and varying levels of the
constant catch thereafter.
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BET Effects of current regulations

• Multi-year Conservation and Management Program
  Rec04-01 sets
• TAC for Major Countries at 90,000 t.
• A specific limit for the number of vessel for
  several country/entity.
• Closure for surface fisheries in the area 0-5N,
  10 W-20W during November (in the Gulf of
  Guinea).
• The closure is much smaller in time and space
  compared to the previous one. Need to expand it
  if we want to be more effective.

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BET Trend in catches of small BET
Figure 8.
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BET Management Recommendation

• Projection indicates that catches of 85,000 t or
  less will permit the stock to rebuild in the
  future.
• However, if the entire catch limit set under
  04-01 were to take and others stayed at recent
  level, the total catch could exceed 100,000 t.
• Considering above, the Committee recomends that
  the total catch not exceed 85,000 t.

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ATLANTIC BIGEYE TUNA SUMMARY Maximum Sustainable
Yield 90,000 t-93,000 t 1 (68,000-
99,000) 2 Current (2006) Yield 65,000
t Replacement Yield 2006 Slightly below
MSY1 Relative Biomass (B2006/BMSY) 0.921
(0.85-1.07)2 Relative Fishing Mortality
FMSY 0.201 (0.07-0.33) 2 F2005/FMSY 0.871
(0.70-1.24) 2 Conservation management
measures in effect Rec. 04-01 replaced
Rec. 79-01 and Rec. 99-01 after June,
2005. - Total allowable catch for 2005 is set
at 81,400 t for major country and
entity - Limits on numbers of fishing vessels
less than the average of 1991 and 1992. -
Specific limits of number of longline boats
China(45), Chinese Taipei (98), Philippines
(8). - Specific limits of number of purse
seine boats for Panama (3). - No purse seine
and baitboat fishing during November in the area
encompassed by 0º-5ºN and 10º W-20º W. 1
Base Case production model (Logistic) results
based on catch data 1950-2005. 2 80 confidence
limits
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BET-Table 1. Estimated catches (t) of bigeye tuna
(Thunnus obesus) by major area, gear and flag.