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Objectives

Is there a ‘cryptic biomass’ of relatively old and large red snapper in southeast US continental shelf-break waters?. Objectives. 27 fa. 16 fa.

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Objectives

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  1. Is there a ‘cryptic biomass’ of relatively old and large red snapper in southeast US continental shelf-break waters?

  2. Objectives 27 fa 16 fa • Determine whether red snapper from high-current, continental shelf-break waters (>27 fa) are, on average, more abundant, older and larger than those from shelf waters (<27 fa) • Assess benefit of establishing a longline survey for red snapper in shelf-break waters GA FL

  3. Methodology 27 fa 16 fa • Study area: center of red snapper abundance • Survey methods determined collaboratively with industry representatives • Survey gear: bottom longline • Effective in high-current, shelf-break areas • Survey design • Three depth strata • Eight latitude bands • N=4 longline sets in each of 24 depth x latitude cells • N=96 sets total GA FL

  4. Methodology 27 fa 16 fa • Survey carried out by experienced commercial fishers during Sept 2010 – Jan 2011 • Survey locations within each cell determined by fishers • 150 total hooks per set, divided evenly between 13/0, 14/0, 15/0 circle hooks • All surveys accompanied by fishery observer responsible for data collection • Fish ages determined from otoliths GA FL

  5. Results • 96 sets made (shown at right) • 32 per depth strata • N = 218 red snapper • Shallow = 93 • Middle = 76 • Deep = 49 • Age range: 3–15 years • Size range: 48–96 cm TL • Greatest number of red snapper caught on one longline set = 19 • 57% of sets = 0 red snapper GA FL

  6. Catch-per-unit-effort • CPUE (mean catch per longline) did not vary significantly by depth or latitude band • No clear trend by depth or latitude • No evidence of greater abundances in shelf-break waters

  7. Age by depth strata: no evidence of relatively older fish in shelf-break waters

  8. Mean age per longline set as a function of depth: no evidence of older fish in shelf-break waters Shelf Shelf-break

  9. Mean length per longline set as a function of depth: no evidence of larger fish in shelf-break waters Shelf Shelf-break

  10. Conclusions • Cryptic biomass hypothesis not supported by longlining data • No evidence of greater abundances, ages or sizes of red snapper in shelf-break waters • Ages surveyed suggest age truncation of the population similar to that identified in the SEDAR 24 assessment

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