Date of Award

Spring 2018

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Chair

Robert T. Leaf

Committee Chair Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 2

Nancy J. Brown-Peterson

Committee Member 3

Kevin S. Dillon

Committee Member 3 Department

Coastal Sciences, Gulf Coast Research Laboratory

Abstract

Red Drum (Sciaenops ocellatus) are highly targeted recreationally in the Gulf of Mexico, and support a small commercial fishery in Mississippi. Despite their popularity, the stock is assessed using data limited approaches that necessitate accurate life history information. I estimated the year-specific and year-aggregated escapement rates for the Mississippi stock (years 2004 to 2015), which were sensitive to mortality estimation methods; year-aggregated estimates were 6.9 to 28.2 % depending on the method, but temporal patterns were consistent. I then addressed concerns with previously estimated life-history characteristics by describing the sex-specific growth and reproductive dynamics. The three-parameter von Bertalanffy growth function was the best candidate length-at-age model, with no significant difference in overall growth between sex-specific relationships, but females had a larger mean asymptotic length, and four candidate models showed significant sexual dimorphism. I described Red Drum as batch spawners, with 3.7 days between successive spawns during the spawning season (August and September). The age at 50% maturity was around age-3 y in both sexes, but spawning capability was not evident until around age-6 y. The carbon (delta C-13) and nitrogen (delta N-15) stable isotope composition of Red Drum muscle tissue was more enriched in carbon offshore and was significantly different with respect to reproductive phase. Mean and variance of delta N-15 and variance of delta C-13 was significantly different between fish < age-7 y and those older. When accounting for muscle turnover rates, this coincides with the age of spawning capability, indicating an ontogenetic migration at age-6 y.

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