Date of Award

2024

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Biological Sciences (MS)

Administrative Home Department

Department of Biological Sciences

Advisor 1

Jill A. Olin

Committee Member 1

James Junker

Committee Member 2

Charlie Martin

Abstract

Resident saltmarsh nekton, namely Cyprinodontiform fishes, play key ecological roles in supporting terrestrial and aquatic food webs. These fishes are highly abundant across the saltmarsh landscape of coastal Louisiana and have evolved to tolerate the highly variable environmental conditions that are characteristic of these habitats. The objective of this research is to consider mechanisms enabling this diverse community of fishes to cooccur in the spatially limited saltmarsh habitats of coastal Louisiana. In Chapter 2, bulk stable isotope ratios of carbon (δ13C), sulfur (δ34S) and nitrogen (δ15N) were used to quantify the intra- and inter-specific resource use of six sympatric Cyprinodontiform fish species residing in saltmarsh ponds. Stable isotopes were used to calculate trophic niche indices that collectively revealed differences in species- and pond-level niches of fishes belonging to the genus Fundulus, suggesting that abundances may strongly influence resource use. In Chapter 3, behavioral feeding trials were used to test how interspecific competition from abundant gulf killifish affects the foraging behavior and food preference of two co-occurring species, diamond killifish and sheepshead minnow. Behavioral trials indicated that higher gulf killifish densities resulted in decreased consumption by diamond killifish but showed increased foraging rate with a shift in food preference, whereas sheepshead minnow consumption stayed consistent. This research provides insights into how these species may respond to high levels of competition for resources in these pond habitats.

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