Defense Date

8-8-2025

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

Tracey Sutton

Second Advisor

Jon Moore

Third Advisor

David Kerstetter

Keywords

Scombriformes, Stromateoidei, driftfish, mesopelagic, gelatinous zooplankton, Gulf of Mexico

Abstract

The suborder Stromateoidei contains 80 species of mesopelagic fishes in five families distributed throughout temperate and tropical seas worldwide, including the Gulf of Mexico (Gulf hereafter). Mesopelagic fishes, especially those that spatially aggregate, serve as important forage items for commercially, recreationally, and ecologically important species of fish, marine mammals, and seabirds. However, knowledge of the ecology and trophic importance of stromateoid fishes in the Gulf is extremely limited. This study provides quantitative information on the species composition, abundance, distribution, and biomass contribution of the stromateoid species to the Gulf deep-pelagic fish assemblage, with comparison to “archetypal” mesopelagic fish families (e.g., the Myctophidae, Gonostomatidae). The Nomeidae and Ariommatidae were the most abundant families, with Cubiceps pauciradiatus being the overwhelmingly dominant species. Size-frequency distributions were found to be dictated by sampling method, with adults being more successfully sampled by large midwater trawls (LMTs) and juveniles by an opening-closing rectangular trawl. The underrepresentation and underappreciation of the ecological importance of stromateoid fishes in the Gulf likely stems from the lack of LMT use in faunal surveys prior to this study. Examination of specimen number per LMT trawl suggests shoaling of adult C. pauciradiatus, possibly related to spawning season. Finally, an annotated inventory of 20 stromateoid species found in the Gulf is provided to consolidate new and historical taxonomic and ecological research.

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