Date of Award

Fall 12-2018

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

School

Ocean Science and Engineering

Committee Chair

Frank Hernandez

Committee Chair School

Ocean Science and Engineering

Committee Member 2

Robert Griffitt

Committee Member 2 School

Ocean Science and Engineering

Committee Member 3

Alison Deary

Abstract

The northern Gulf of Mexico experiences high levels of freshwater runoff annually from various sources including the Mississippi River and Mobile Bay, among other sources. Early life history stages of fishes are especially vulnerable to environmental variability created by freshwater discharge. The objectives of this study were to describe the available prey field, diet, growth and condition of larval fishes with respect to various effects of freshwater discharge in the northern Gulf. The first chapter compared these parameters in larval Gulf Menhaden (Brevoortia patronus) collected from three different water masses characterized by physical and biological parameters after the opening of the Bonnet Carré Spillway in January 2016. Zooplankton community structure was found to be significantly different among the water masses. Larval Gulf Menhaden diet did not differ significantly among the water masses, but larvae from the Chandeleur Sound region had significantly lower recent growth and poorer condition than larvae from the other regions. The second chapter addressed the same parameters in Atlantic Bumper (Chloroscombrus chrysurus) in relation to summer-time hypoxia. Although found in a reduced habitat, the larvae collected above hypoxia did not experience differences in prey field, diet, growth, or condition based on morphometric analyses. Overall, my studies exemplify how difficult it is to predict results of environmental variability on larval fishes.

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