Semester of Graduation

Fall 2018

Degree

Master of Science (MS)

Department

Oceanography and Coastal Sciences

Document Type

Thesis

Abstract

Growth models estimate life history parameters that are used in the management of fisheries stocks. The most commonly used growth model in fisheries is the von Bertalanffy growth model (VBGM), yet it has been shown to provide a poor fit for length-at-age data of some species and other models exist. I reviewed 196 peer-reviewed age and growth studies and 50 NOAA stock assessments to examine temporal trends in the use of growth models and model selection in fisheries. I found that the use of multi-model frameworks has increased since the year 2000 and information theoretic approaches are replacing goodness-of-fit and a priori model selection in fisheries studies. However, NOAA stock assessments rely almost exclusively on the von Bertalanffy growth model. Furthermore, factors such as the study location, and maximum age, usually did not contribute to the final model selected.

I then performed a multi-model evaluation of growth models to (1) determine the best-fitting growth model for black drum (Pogonias cromis), red drum (Sciaenops ocellatus), and spotted seatrout (Cynoscion nebulosus) length-at-age data from coastal Gulf of Mexico; and (2) to evaluate the variation among state-wide and sex-specific parameter estimates. I found that sex-specific models were better fitting than pooled models, black and red drum were fit best by biphasic models, and spotted seatrout by seasonal and sigmoidal models. Texas fish were estimated to grow to larger sizes and Louisiana fish grew at a faster rate. Lastly, I modeled estuary-specific growth rates of black drum, red drum, and spotted seatrout up to age-3 and incorporated static spatial drivers as covariates into hierarchical linear models to evaluate the (1) spatial variation of growth rate among estuaries and (2) effect of static spatial drivers on the spatial variation of growth rate among estuaries. I found significant variation among estuary-specific growth rates; furthermore, distance of marsh edge and estuary depth had a moderate effect in driving the variation in growth rate of female spotted seatrout and black drum, respectively. Because of sciaenid’s significant importance in the Gulf of Mexico, a deep understanding of the dynamics of their growth is of critical value to fisheries managers.

Date

10-16-2018

Committee Chair

Midway, Stephen

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