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2007 ICCAT SCRS Executive Summay for Atlantic Bigeye Tuna.
BiologyDistribution : 50N-45S, not in MediterraneanSwimming Behavior : extensive vertical movement, deeper during daytime, shallower at night.Spawning : tropical-subtropical, mature at age 3Nursery : Gulf of GuineaPrey : fish, mollusk, crustaceanGrowth (relatively fast) : Age 3 (105 cm), Age 5 (140cm), Age 7 (163cm)Schooling behavior : Juveniles are mixed with yellowfin and skipjackNatural mortality : estimated by tagging dataStock structure : Atlantic wide
Fisheries : LL(45-50kg), North BB(20-30kg), PS+Trop BB(3-4kg)
LL : Japan, Chinese Taipei, China, Philippines
PS : EC-Spain+France, Ghana, Venezuela (in association with FADs)
data is important
& improved for Ghana
is 65,000 t
Geographic distribution of bigeye catches for most recent years (2002-2005) by major tuna fishery.
Unreported catches estimated from trade statistics.
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.
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.
Trajectories of B-ratio and F-ratio obtained from ASPIC base case run.
MFCL run results. Selectivity curve for each decade (left). MSY estimates.
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).
Stock projections by ASPIC model assuming a catch of 71,000 t in
2006 and varying levels of the constant catch thereafter.
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.
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 theaverage 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.
280% confidence limits
BET-Table 1. Estimated catches (t) of bigeye tuna (Thunnus obesus) by major area, gear and flag.