SCRS Assessments of Western Atlantic Bluefin Tuna Clay E. Porch Southeast Fisheries Science Center U.S. National Marine Fisheries Service

OUTLINE DATA METHODS ASSESSMENTS PROJECTIONS RESULTS OF 2006 ASSESSMENT KEY SOURCES OF UNCERTAINTY

DATA Total catch (TASK I) Landings + dead discards

DATA Total catch (TASK I) Catch at size (TASK II) Size frequencies of samples (by nation, fleet, gear, time/area) raised to total catch

Quality of Size Data LL RR/HL PS All commercial landings in Canada and US measured Japanese longline not well sampled for size Other fisheries adequate Some historical gaps (substitutions!) 1980

DATA Total catch (TASK I) Catch at size (TASK II) Indices of abundance (GLM) Larval survey Canada TL (SWNS, GSL) 10+ US RR (NE US, various sizes) Japan LL (GOM, Area 2)2-10+ US LL (GOM)10+

Indices of abundance No consistent changes in CPUE

DATA Total catch (TASK I) Catch at size (TASK II) Indices of abundance (GLM) Tagging Conventional Electronic?

METHODS Converting Catch at size (CAS) to Catch at age (CAA) Age data from reading hard parts rare, but size data are more plentiful Method of choice has been age slicing (assigns range of lengths to specific age classes)

Age-slicing (program AGEIT) 1.Assumes growth curve known consistently assign too young or old 2.Assumes equal overlap in lengths of adjacent age classes smears year classes (smooths CAA) difficult to age older fish (plus groups) 3.Alternatives Age-length keys, Multifan

METHODS Age-slicing (Convert CAS to CAA) Standardizing CPUE (GLM) Stock assessment algorithm Base model: ADAPT VPA Others examined: Production ASPM SCA

ADAPT SPECIFICATIONS Terminal selectivities: F 1 = 0.318F 2, F 3 =F 2, F 5 =F 4, F 7 =F 6, F 9 =F 8 F-ratios (F 10 /F 9 ): estimated 1981-lognormal prior (1.14,0.25) Indices: lognormal, equal variance Natural mortality: constant at 0.14

PROJECTION SPECIFICATIONS Recruitment: constant at mean ( recruitments deemed unreliable and replaced by mean) Fishing: selection/avail. = mean (last year, 2004, deemed unreliable) Mixing: negligible

Consistent with 2002 SA Less optimistic estimates of 1994 and 1997 year classes More optimistic view of recent F’s RESULTS OF 2006 ASSESSMENT

Projections

Current (2006) Catch (including discards) 1,929 t Short-term Sustainable Yield ~2,300 t Maximum Sustainable Yield (MSY|R)3,200 (3,000-3,400) Relative Spawning Stock Biomass B2004/B B2004/BMSY|R0.41 ( ) Relative Fishing Mortality 3 F2004/FMSY|R1.7 F2004/F F2004/Fmax1.7 Management Measures: 2,100 t TAC from 2007 inc. dead disc [Rec ] 2,700 t TAC from 2003 inc. dead discards [Rec ] 30 kg (115 cm FL) min. size with 8% tol. [Rec ] No directed fisheries in Gulf of Mexico [Rec ] F2004 is taken to be the geometric mean of the estimates for BFTW summary table

State of stock: low U.S. catches Plausible explanations (1) that availability of fish to the United States fishery was low (2) the overall size of population in the west declined substantially Evidence (SCRS/2007/171) (1) Canada and Japan did not have abnormally low catches CPUE series from Gulf of St. Lawrence at high levels since 2004 CPUE series from GOM do not show consistent decline (2) some abundance indices suggest decline declining size composition in some areas small changes in F suggested by tag data despite declining catches Conclusion (1) No strong evidence to favor either explanation over the other (2) However, the failure of a fishery to take half of its TAC for several years, and other new evidence reviewed by the committee, heightened concern that the estimate of stock status from the 2006 assessment may be optimistic

Management recommendations Commission responded positively, making Rec , which establishes a quota of 2,100 MT However, the Committee is even more concerned about status of west stock than it was a year ago. Further advice provided after the next assessment (2008). Evidence accumulating that both productivity of west stock and west bluefin fisheries linked to the east stock. One plausible explanation for failure of west fishery to take TAC in recent years is that it is partly dependent on east fish, and east fish now less available to the west Therefore, management actions taken in the eastern Atlantic and Mediterranean are likely to impact recovery in the west Atlantic (SCRS 2006 Agenda Item 15.6.)

BFT Statement of work Data Submission: “It is essential, in particular, that catch, catch-at-age and tagging data through 2006 be final a few months prior to the meeting to allow preparatory works and analyses. Data through 2006end March 2008 Data for week prior

BFT Statement of work Assessment: “In the case of the West stock, mainline advice should be based on results from validated and documented software retained in the ICCAT catalog. These catalog entries need to be completed by April 2008”

BFT Statement of work Assessment: 1.Update 2006 assessment (VPA) 2.VPA using new age-growth info.

BFT Statement of work Assessment: 1.Update 2006 assessment (VPA) 2.VPA using new age-growth info. 3.VPA using new reproductive info.

Age of BFT in LL landings from GOM

BFT Statement of work Assessment: 1.Update 2006 assessment (VPA) 2.VPA using new age-growth info. 3.VPA using new reproductive info. 4.VPA with mixing Using conventional tag data Using electronic tagging data Using results from otolith comp.

BFT Statement of work Assessment: 1.Update 2006 assessment (VPA) 2.VPA using new age-growth info. 3.VPA using new reproductive info. 4.VPA with mixing Using conventional tag data Using electronic tagging data Using results from otolith comp. 5.Alternative models Multi-area tag-recapture

ONE STOCK ( ) Trans-Atlantic tag rec. TWO STOCKS (1980-present) 2 spawning grounds Distinct biol. char. Catch distribution Small interchange ONE STOCK ( ) Trans-Atlantic tag rec. TWO STOCKS (1980-present) 2 spawning grounds Distinct biol. char. Catch distribution Small interchange

ESTIMATION: CONVENTIONAL TAGS T ew (%) T we (%) DIFFUSION OVERLAP

NO MIXINGDIFFUSION OVERLAP AIC=2870 AIC=893AIC=897 T=(0.4, 7.6)%T=(0.0, 11.4)% RESULTS WITH POP-UP TAGS

1) Improper accounting of fates 2) Limited coverage in time and space 3)How to interpret fine-scale motions on coarse model grid (e.g., two-area VPA) 4)Eastern contamination PITFALLS OF USING TAGS

4) Eastern contamination PITFALLS OF USING POP-UP TAGS

Otolith microconstituent analysis L =  n sy  p asy log p asy Assuming samples taken at randon from catch WHAT ELSE? ^

Projection assumptions WHAT ELSE? Beverton & Holt vs. regime shift?

Photo acknowledgments Barbara Block Molly Lutcavage Eric Prince NOAA Photo Gallery Photo acknowledgments Barbara Block Molly Lutcavage Eric Prince NOAA Photo Gallery QUESTIONS?