Date of Award

Spring 2020

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Program/Concentration

Biology

Committee Director

Ian Bartol

Committee Member

Holly Gaff

Committee Member

Kent Carpenter

Committee Member

Damon Gannon

Abstract

This study describes the diet of bottlenose dolphins (Tursiops truncatus) stranded in Virginia via stomach content analysis and considers factors such as proportion of numerical abundance and reconstructed mass, frequency of occurrence, average reconstructed prey size, prey diversity and quantity, and otolith degradation code. Fish size was estimated via regression equations established from local fish collected during the study that derive wet weight directly from otolith length or width. Squid size is estimated from previously published equations. Soniferous fishes dominated the diet, especially Atlantic croaker, spot, and seatrout spp., adding evidence to the theory that bottlenose dolphins passively listen for their prey. Noise pollution should be an important consideration for the conservation of this species. The diet was influenced by ontogenetic and seasonal changes. Prey that are relatively difficult to capture or not available to calves due to habitat, such as striped bass or longfin inshore squid, were absent in the diet of that age class. However, easy to capture prey, such as spot, became progressively less important with age. Seasonal variation in the diet was observed, with differences likely being due to changes in prey availability (due to seasonal migrations) and detectability (due to increased vocalizing during spawning) rather than changes in prey preference. Lastly, the stomachs of dolphins with external evidence of an entangling interaction contained a significantly higher proportion of recently ingested fish (using otolith code as a proxy) than those that did not. The presence of recently ingested prey is commonly referenced as an indicator of peracute underwater entrapment; however, this is the first study to quantitatively establish a significant relationship. The data presented in this study promise to enhance policy and management by establishing baseline information on natural history as well as a quantitatively assessed indicator for peracute underwater entrapment that can be referenced to study local shifts in natural history or incidence of bycatch.

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DOI

10.25777/6bas-rj82

ISBN

9798641222868

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