2007 ICCAT SCRS Executive Summay for Atlantic Bigeye Tuna

2. 2007 ICCAT SCRS Executive Summay for Atlantic Bigeye Tuna

3. 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

4. BETCatch 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) Figure 1. Species composition data is important & improved for Ghana 2006 catch is 65,000 t

5. BETCatchDistribution Figure 2. Geographic distribution of bigeye catches for most recent years (2002-2005) by major tuna fishery.

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

7. BET abundance Indices Figure 4-1.

8. BETabundance Indices Figure 4-2. New CPUE

9. BET Abundance Indices

10. 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. 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.

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

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

13. 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).

14. 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.

15. 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.

16. BET Trend in catches of small BET Figure 8.

17. BETManagement 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.

18. 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 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

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