Abundance, age distribution, growth rate, and mortality estimations for red snapper, Lutjanus campechanus, around gas platforms and other artificial structures in the northeast Gulf of Mexico

Abstract

We estimated red snapper Lutjanus campechanus, abundance, age frequency, fecundity, and
mortality, through a fishery independent survey. We tested six capture methods: bandit rigs, gill
nets, fish trap, hook-and-line, drop net, and spear gun. After fishing, we used SCUBA visual counts
to estimate remaining red snapper. All captured fish were weighed, measured, otoliths removed and
ovaries weighed and preserved in Gilsons. We captured 1,147 red snapper at 28 different artificial
reefs. Mean + Sd abundance per reef = 86.3 + 69.4. Estimated population size off Alabama from 15
to 73 m depths = 1.3 million red snapper. Mean size = 279 + 59 mm SL, and mean age was two
years. We captured 442 females with 32 % mature. Spawning duration was 142 d, with peaks from
May through July. Batch fecundity = 83,870 eggs per fish, with annual fecundity = 2.9 million eggs
per fish. Fish trap was the best capture method and SCUBA visual survey was the best abundance
estimator. Females start maturing above 250 mm SL, and GSI peaked May to August. Total
mortality was high (Z = -2.0) over the year classes sampled. Growth rates were 140 mm TL per year.
Abundance estimates may be low, because we sampled only heavily fished reef sites, and future
efforts will be directed at “unpublished” reef sites.