2007 ICCAT SCRS Executive Summay for Atlantic Bigeye Tuna 2007 ICCAT SCRS Executive Summay for Atlantic Bigeye Tuna

Biology 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

BET Catch 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) 2006 catch is 65,000 t Species compositio n data is important & improved for Ghana Figure 1.

BET Catch Distribution Geographic distribution of bigeye catches for most recent years ( ) by major tuna fishery. Figure 2.

BET Catch Unreported catches estimated from trade statistics. Figure 3.

BET abundance Indices Figure 4-1.

BET abundance Indices Figure 4-2. New CPUE

BET Abundance Indices

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. BET Assessment Models 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.

BET Model Results Estimated MSY : 90,000 – 93,000 t Trajectories of B-ratio and F-ratio obtained from ASPIC base case run. Figure 5.

BET Model Results MFCL run results. Selectivity curve for each decade (left). MSY estimates. 1960s 1990s 1980s 1970s 2000s MSY estimates

BET Model Results 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). Figure 6.

BET Outlook Stock projections by ASPIC model assuming a catch of 71,000 t in 2006 and varying levels of the constant catch thereafter. Figure 7. 85K

BET Effects of current regulations Multi-year Conservation and Management Program Rec[04-01] 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 ˚ -5 ˚ N, 10 ˚ W-20 ˚ W 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.

BET Trend in catches of small BET Figure 8.

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 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.

ATLANTIC BIGEYE TUNA SUMMARY Maximum Sustainable Yield 90,000 t-93,000 t 1 (68, ,000) 2 Current (2006) Yield 65,000 t Replacement Yield 2006 Slightly below MSY 1 Relative Biomass (B 2006 /B MSY ) ( ) 2 Relative Fishing Mortality F MSY ( ) 2 F 2005 /F MSY ( ) 2 Conservation & management measures in effect: [Rec ] replaced [Rec and Rec ] after June, − 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 − 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 % confidence limits

BET-Table 1. Estimated catches (t) of bigeye tuna (Thunnus obesus) by major area, gear and flag.