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North and South Atlantic albacore (Thunnus alalunga) stocks assessment ICCAT WG ALB, 26 Sept., 2007 PowerPoint Presentation
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North and South Atlantic albacore (Thunnus alalunga) stocks assessment ICCAT WG ALB, 26 Sept., 2007

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North and South Atlantic albacore (Thunnus alalunga) stocks assessment ICCAT WG ALB, 26 Sept., 2007

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  1. Ex. Report ALB SCI-017 North and South Atlantic albacore (Thunnus alalunga) stocks assessment ICCAT WG ALB, 26 Sept., 2007 Multifan Inputs for ALB Assessment, March 2007 SCI-030 /2007 Detail Albacore stock assessment, July 2007- SCI-036 /2007

  2. ALB- Atlantic Biology • Stock structure for assessment: North and South stocks in the Atlantic ocean separated at 5º and Mediterranean stock. Intermingling of Indian and Atlantic oceans needs research. • Present knowledge on habitat distribuition by size, spawning areas, maturity based on limited studies mostly from past years. • Revised vB growth equation was estimated for South Atlantic stock based on aging dorsal fin ray section • Vertical distribution: immature at sub-surface above thermocline in summer. Adult distribution at wider range from surface to ~ 300m depth.

  3. ALB - Spatial distribution based on average catch 2000 - 2005 period

  4. Catch trend Northern stock ALB 1930-2005 years 1975 VPA LL TROL BB

  5. Fisheries indicators in North Atlantic Overall description • Targeting immature and sub-adults (50- 90 cm FL) by surface fisheries in the North Eastern Atlantic from Azores Is. to northern lalitude (SW Ireland) and Bay of Biscay areas, during spring, summer and autumn. • Targeting immature and adult albacore (60-130 cm FL) by longline fisheries in Central and Western Atlantic waters all year round. • Catch was extended back to 1930 after revision for stock assessment. • Trend: declining began in 1986 due to reduction of traditional surface fleets (Troll and Baitboat) and longline fleets. Stabilization observed in the 90´s due to incorporation of new fleets (drifnets & mid-water pair pelagic trawl). Maximun catchof 38,063 t registered in 1993. Followed by the lowest on record of 22,685 t in 2002. Since then and steady increase until reaching a peak of 36,077 t in 2006. LL TROL BB

  6. Surface Fisheries Gears: troll, baitboat, mid-water pair pelagic trawl (MWPT). Main fleets involved: EC (Spain, France Portugal and Ireland) In 2006 the surface fishery represented the 86 % of total catch in North stock EC-France MWPT reported the highest catch of recent years in 2005, but decreased the 30 % in 2006. EC-Ireland MWPT catch has decreased since 2002. EC-Spain increased the baitboat catch by 49% respecting 2005 catch and the troll catch in 2006 was similar to 2005 level. LL Longline Fisheries BB Longline catches decreased in 2006, due to a decrease of landings by Chinese-Taipei fleet of 60% compared to 2005 caused by decline in fishing effort.

  7. Catch trend Southern stock ALB 1956-2005 years LL LL BB LL BB

  8. Fisheries indicators in South Atlantic Overall description Targeting immature and sub-adults (70- 90 cm FL) by surface fisheries in the South Eastern Atlantic in coastal waters of Namibia and South Africa from October to May. Targeting adult albacore (> 90 cm FL) by longline fisheries in Northeast coast off Brazil (5ºS-20º S) and over the South Atlantic area by longline fleet from Chinese-Taipei Central all year round. Trend: total reported catch in 2006 was 24,375 t , an increase of about 5,000 t respect 2005. TheChinese –Taipei catch increased in 2006 to 12,293 t. As for Brazilian catches, the Chinese –Taipei vessels (incluidng Belize and St. Vincent flagged boats ) stopped fishing for Brazil in 2003, then albacore was only caugth as by-catch in the SWO and Trop target longline fisheries, reaching 267 t. The decreased of albacore in 2006 in inshore waters of South Africa and unfavorable foreign currency has caused a reduction in number of active baitboat vessels. LL TROL BB

  9. Catch trend Mediterranean stock ALB 1964 -2005 years Main Fleets Longline Other Surf LL LL BB LL BB • Reported catches in 2006 were 5,874 t, an increased with respect to 2005.

  10. Assessing the State of Atlantic stocks Background • Thorough revision of North and South Atlantic stock data: Task I and Task II, was done and more robust method was implemented to analyse Catch-at-Size (CAS) information. • Historical Catch for North Atlantic stock was recovered and incorporate to the analyses up to 1930. • Catch rates analyses were reviwed and new model applied for some longline fleets resulting in better fit to data. • Substantial work was undertaken to implement new methods which do not assume that CAA is known whitout error, to assess the albacore stocks. • This new implemented method provided the opportunity to evaluate a range of hypothesis: - how the fisheries operated over time and their impact in the population ? LL LL BB LL BB

  11. ALB- North stock. Total Catch-At-Age (CAA) 1 to 8+ age group Bubble size proportional to number of fish

  12. ALB- North stock. Catch-At-Age (CAA) by Fishery 1 to 8+ age group LONGLINE FLEETS Target Ch-TAI By-catch USA By-catch By-catch JPN SURFACE FLEETS Target BB ESP Target TR ESP Target OTHER Bubble size proportional to number of fish on each fleet

  13. ALB- North CPUE time series Surface TR fleet Longline Taiwan LL target

  14. ALB-N- Recruitment and Spawning stock Age 1- recruit MFCL model 2005 high but uncertain 1930- 2005 MFCL model SSB ~ ¼ Max in 40´s

  15. ALB- N- Relative F, SSB and status stock relative to MSY

  16. ALB- North State of stock SSB has decreased to one fourth of the SSB in the highest level in the 40´s Recruit decreased from the 60´s until 2004. In 2005 the estimated recruitment is high ~ 60´s, but magnitude is uncertain. The stock rebuild to levels near BMSY (SSB 20% below MSY) vs 2000 assessment when SSB 50% below MSY Current F is 50% above F msy Estimates of MSY varied over time as a combination of surface and longline fisheries with changing selectivity pattern over time period. MSY for 3 recent years ~ 32.000 t , but over time ranged from 26.000 t to 34.00 t.

  17. ALB- North Atlantic Fishing trajectory and 2005 status status in 2005 1930-2005 evolution of relative biomass and fishing mortality estimated trajectory relative to MSY

  18. ALB- North Atlantic Uncertainty of 2005 status determination 2005 status F/Fmsy =1.5 B/Bmsy = 0.81

  19. ALB- N- Projections 2006 CATCH of 36.000 t 32.000 t TAC of 34.500 t VPA relative SSB (SSB/SSBMSY)for scenarios of cte catch 2008 -2020 Projected Current catch for 2006 & 2007

  20. ALB- N- VPA Projections scenarios assuming strong year class 32.000 t TAC 34.500 t TAC relative SSB (SSB/SSBMSY)for scenarios of cte catch 2008 -2020 Projected Current catch for 2006 & 2007

  21. ALB- South stock. Total Catch-At-Age (CAA) 1 to 8+ age group Bubble size proportional to number of fish

  22. ALB- South stock. Catch-At-Age (CAA) by Fishery 1 to 8+ age group LONGLINE FLEETS Target Ch-TAI Target and By-catch BRA By-catch JPN SURFACE FLEETS Target BB SA Target BB NAM Target OTHER Bubble size proportional to number of fish on each fleet

  23. ALB – South CPUE time series Longline Taiwan Target Surface Baitboat

  24. ALB- South Atlantic Fishing trajectory and 2005 status

  25. ALB- South Atlantic Uncertainty of 2005 status determination 2005 status F/Fmsy =0.63 B/Bmsy = 0.9

  26. ALB- South State of stock Last assesmment was done in 2003 Longline CPUE ´show a declining trend at the begining of time series, less marked in the recent period. Thos indices traget adult albacore. Surface CPUE´s (Baitboat) target mostly immature albacore and no trend is seen. Current SSB has declined 25% from unfished SSB. Accordingly it is likely that in 2005 SSB is about 90% of Bmsy and F is 40% below F msy Estimates of current MSY is around 33.300 t and Replacement yield is around 29.000 t, current catch 24.460 t is below.

  27. ALB- S- Projections 10 years projections BMSY SSB over time trend and 80% confidence bounds Projected cte catch = 25.000 t

  28. ALB- N MANAGEMENT Rec. • Current TAC is 34.500 t • 2005 and 2006 catches have been above • Projections indicate that stock will not recover from overfished state if catch level remain > 30.000 t • If strong year class enters the fishery the stock would recovered faster ALB- S MANAGEMENT Rec. • Current TAC is 29.900 t • 2Recent catches have been below • Projections indicate that catches at 2006 level will recover the stock from overfished state • Current management scheme is sufficient for recovery of South stock

  29. THANKS