Theses and Dissertations


Title: A fishery-independent survey of red snapper, Lutjanus campechanus, from the northern Gulf of Mexico

Name: Moss, Dustin Robert

Degree: MS

Chair: Stephen T. Szedlmayer

Resides:

University: Auburn University

Location: Auburn, Alabama

Date: 2003

Pages: 71

Keywords: Red Snapper,survey

Abstract:

Fishery independent samples were taken to determine age structure, abundance, mortality, growth, and reproductive characteristics for the red snapper population off Alabama, USA. Spawning stock biomass models were used in stock assessment. Seven methods were used to estimate red snapper abundance: fish trap, hook-and-line, bandit gear, drop net, speargun, gill net, and SCUBA visual surveys. Growth, length-weight relation, and spawning season were similar to past studies. The annual fecundity-age and annual fecundity-total length relations were linear: annual fecundity = 2.6 x 106 (age) - (5.3 x 106), R2 = 0.93, annual fecundity = 3.8 x 104 (total length) -(1.4 x 107), R2 = 0.84. Abundance estimates ranged from 0 to 234 fish per reef with mean abundance ± SD - 86 ± 71. The fish trap (CPUE ± SD = 28.02 ± 33.97) and hook-and-line (CPUE ± SD = 2.21 ± 2.66) were the most effective collection gears.The fish trap caught significantly smaller fish compared to hook-and-line (P<0.05). However, both methods appeared size biased, as larger fish were routinely observed with SCUBA visual surveys. Total instantaneous annual mortality was 0.43 or 1.00 based on catch-curve regression. Estimates of spawning potential ratio ranged from 1.20 to 22.57%, were dependent on assumed levels of juvenile and adult mortalities, and most were below the target spawning potential ratio of 20%. However, mortality may have been overestimated due to gear bias, which captured disportionately younger fish. The present mortality, spawning potential ratio, and yield were only estimated from heavily fished reef sites (i.e. public reef sites) and other unpublished (more lightly fished) locations may show contrasting estimates.

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