Date of Award

2021

Document Type

Thesis

Degree Name

Bachelors

Department

Natural Sciences

First Advisor

Gardiner, Jayne

Area of Concentration

Marine Biology and Environmental Studies

Abstract

River systems are an understudied habitat type for elasmobranchs. In order to predict habitat use and partitioning across maturity states within the Manatee River, Florida, elasmobranch catch rates and environmental factors were analyzed using data from the 2018 to 2020 Gulf of Mexico Shark Pupping and Nursery (GULFSPAN) gillnet and longline survey. Boosted Regression Tree (BRT) analysis was conducted to determine the major environmental factors that impact species presence. General Linear Model (GLM) analysis was conducted on the principal species to determine significant environmental factors across species’ lengths. The Atlantic Sharpnose Shark (Rhizoprionodon terraenovae), Blacktip Shark (Carcharhinus limbatus), Bull Shark (Carcharhinus leucas), Cownose Ray (Rhinoptera bonasus) and Bonnethead Shark (Sphyrna tiburo) were the principal species of study. Depth, dissolved oxygen, and salinity were the most influential environmental factors across species for the BRT models. The GLMs determined salinity, day length, and depth as significant factors within most principal species. Habitat partitioning can be seen in and between several species despite the small study area. This research highlights the need to determine habitat preferences in order to better understand elasmobranchs movements within river systems, which will aid in conservation efforts for these species.

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