Black Sea Bass – Northern Stock Coastal-Pelagic/ASMFC Working Group Review June 15, 2010

Update of assessment approach adopted by the Data Poor Stocks Working Group ( Dec 2008) and the 2009 assessment (June 2009). Approach: Length-based model of population parameters - require time series of catch, survey indices Compare results to biological reference points to determine stock status Produce projections based on model results

Life History – Distributed Maine through Gulf of Mexico Managed as single stock north of Cape Hatteras Protogynous hermaphrodite: Transition to male at age 2-5 Seasonal migrations inshore/offshore Maximum age 15 (?) 50% mature 21 cm

Black sea bass size at maturity from NEFSC spring surveys

2008 and 2009 commercial black sea bass landings

Values in blue - estimates from commercial ratio

Recreational Discard weight Discard weight estimated using landing mean weight

OT from observer Pot and handline from VTR estimate from series average

Black sea bass catch estimates Rec discard mortality = 25% Com discard mortality = 25-50%

average sea bass catch components

Combined Recreational/Commercial landings length frequency

Combined Recreational/Commercial landings length frequency

Combined Recreational/Commercial landings length frequency

Mean and Median length of sea bass landings median mean

Northeast Fisheries Science Center Trawl Survey Spring offshore strata 1968 – 2009 (Bigelow conversion coefficient = 3.416) Winter offshore strata 1992 – 2007 Log e transform indices

NEFSC Indices of sea bass adult abundance (>22 cm) (stratified mean #/tow)

NEFSC Spring and Winter indices of juvenile abundance (stratified mean #/tow)

SCALE model

SCALE model (P. Nitschke NMFS,NEFSC) Length based catch at age model Inputs : NEFSC spring ( ) and winter surveys ( ) adult (> 22 cm) and recruitment (< 14 cm) Survey length frequencies ( , ) Fishery catch series ( ) Fishery length frequencies ( ) Selectivity periods ( , , ) Mean length at age and std. deviations Length-weight equation (from survey series) Natural mortality estimate (0.4)

Sea Bass growth used in SCALE Mean length + 2 stdev

Selectivity used in the SCALE model

Model results influenced by presence of juvenile indices, weighting factors, etc. Which is correct model? Adopted model averaging approach (Burnham and Anderson (2002)

Scale modeling approach:

Observed and estimated average (+ 2 std dev) black sea bass catch

NMFS Spring index – predicted vs observed (index +1)

NMFS Winter index – predicted vs observed (index +1)

Wt’d Average Fishing mortality + 2 std dev from SCALE model estimates Fmsy

Wt’d Average Recruitment + 2 std dev from SCALE model estimates

Wt’d Average Total Biomass + 2 std dev from SCALE model estimates Bmsy

Wt’d Average Total Abundance + 2 std dev from SCALE model estimates

Wt’d Average Spawning Stock Biomass + 95% CI from SCALE model estimates

Relationship between SSB and F

Projection approach Use predicted output as new input. Input F for projections and allow model to predict catch. Survey data in 2009 and 2010 treated as missing Catch assumed equal to quota plus average discard lf 5 year average Average spring and winter indices Average recruitment variation, starting recruitment and starting F

Projection if F2010 = F2008

Retrospective patterns in typical model run

Comparison to previous assessments

NEFSC Spring offshore survey- 2004

NEFSC Spring offshore survey- 2005

NEFSC Spring offshore survey- 2006

NEFSC Spring offshore survey- 2007

NEFSC Spring offshore survey- 2008

NEFSC Spring offshore survey