Date of Award

Fall 2013

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Chair

Mark Peterson

Committee Chair Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 2

Paul Mickle

Committee Member 2 Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 3

G. Walter Ingram Jr.

Committee Member 3 Department

Coastal Sciences, Gulf Coast Research Laboratory

Abstract

Stenotomus caprinus (Longspine Porgy) is one of the most abundant bycatch species caught in trawl fisheries in the northern Gulf of Mexico (GOM). Biological data of length, weight, and abundance have been collected since 1972 on the Southeast Area Monitoring and Assessment Program (SEAMAP) surveys with a variety of GOM species, including Longspine Porgy, using trawl nets during groundfish surveys. In 2010-2011 five Longspine Porgy were obtained from Groundfish and Pelagic surveys at each station for further analysis. Age distribution was determined through von Bertalanffy length and weight-age models. The samples were separated into two regions of the GOM to determine if there was a regional growth difference using likelihood methods. Regional von Bertalanffy length-age growth models displayed significantly different growth parameters with fish in the Central region growing larger at a slower rate (k) then those in the West region. Mortality of Longspine Porgy was calculated for each year between 1987-2011 using the catch curve analysis and length-frequency histograms for a method comparison. This resulted in the length-frequency histogram method not being as accurate, therefore would not be a sufficient substitute for the catch curve analysis. Mortality was compared to shrimping effort and abiotic factors through a multiple regression and resulted in shrimping effort having a major influence on Longspine Porgy mortality. A better understanding of age, growth, and mortality of Longspine Porgy may provide information to more effectively evaluate the effect of their high rate of bycatch on other species through trophic cascade or bottom-up effects.

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