Date of Award

Fall 12-2020

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

Kevin Dillon

Committee Member 2 School

Ocean Science and Engineering

Committee Member 3

Mark S. Peterson

Committee Member 3 School

Ocean Science and Engineering

Abstract

Sargassum, a genus of holopelagic brown algae, floats at the ocean’s surface using air-filled bladders and forms a complex comprised of two species, S. natans and S. fluitans. Oceanic processes (e.g., Langmuir circulation, etc.) aggregate Sargassum into mats and weedlines, and primarily distribute the algal complex throughout the North Atlantic Ocean and the Gulf of Mexico (GOM). These floating habitats provide shelter and feeding opportunities for a diverse community of invertebrates and fishes. Sargassum is a presumed nursery habitat for juvenile stages of commercially- and recreationally-targeted fishery species. In this study, I estimated the standardized abundances of juvenile fishes, fish assemblages, and diets of Sargassum-associated fishes in the northern GOM, and investigated temporal, spatial, and environmental variability in these estimates. I observed some interannual variability in fish density and diversity, but species’ distributions were often related to surface chlorophyll, spatial variables, or surface features (Loop Current or associated eddies). Diets were analyzed for juvenile Gray Triggerfish, Greater Amberjack, Lesser Amberjack, Almaco Jack, and Tripletail, and were found to be spatially variable (especially with distance from shelf break). I observed a continuum of dependency on Sargassum for feeding by these different species, from more obligate (e.g., Gray Triggerfish and Tripletail) to transient feeders on the habitat (e.g., Amberjack spp.). The results of this thesis fill a knowledge gap of diet information for Sargassum-associated juvenile fishes in the northern GOM, and provide an understanding of the factors contributing to variability in juvenile fish abundances and assemblages.

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