Comparison of Total Mortality of White Grunt from the Headboat Fishery on the Gulf Coast of Florida during Spawning and Postspawning Seasons

Abstract

White grunts Haemulon plumieri were sampled from catches of the headboat fishery operating on the Gulf Coast of Florida to determine sex-specific total mortality by using catch curve analyses. Sampling was conducted during the peak of the spawning season (April–June) and in a postspawning season (July–October). In total, 1,051 white grunts were sampled in the spawning season, and 1,141 were sampled in the postspawning season. Recruitment to the fishery occurred at age 2, and the majority of males and females landed in the fishery during both the spawning and postspawning seasons were ages 2–4. The maximum age of females sampled was 18 years; for males, the maximum was 15 years. Instantaneous total mortality (Z) estimates from the catch curves did not differ significantly between spawning females, spawning males, postspawning females, and postspawning males; the pooled Z was estimated to be 0.357 (95% confidence interval, 0.284–0.430). Total annual mortality (A) was therefore estimated to be 30% (95% confidence interval, 25–35%). Total annual mortality estimates based on Robson–Chapman survival estimates were similar for females (28% and 30% for spawning and postspawning females, respectively) but were slightly greater for males (37% and 38%, respectively).