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Analysis of Red Snapper Population in Southeast US Continental Waters

This study aimed to determine if older and larger red snapper are more abundant in high-current, shelf-break waters compared to shelf waters. Longline surveys were conducted to assess the population demographics. Results indicate no significant differences in abundance, age, or size of red snapper between the two water types. The study suggests age truncation in the population similar to previous assessments.

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Analysis of Red Snapper Population in Southeast US Continental Waters

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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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