Publication Date

Fall 2014

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Moss Landing Marine Laboratories

Advisor

James T. Harvey

Keywords

acoustic monitoring, estuary, Leopard Shark, movement, sexual segregation

Subject Areas

Biology

Abstract

Estuaries are used seasonally by many elasmobranchs for reproduction and as nurseries. The character, location, and availability of elasmobranch habitats in estuaries are often altered by anthropogenic activities and environmental changes. These habitat changes may have different effects on groups within a shark population because sex-specific segregations are common for many elasmobranchs. Leopard Sharks (Triakis semifasciata) are important estuarine predators in California and exhibit sexual segregations. Movements of 13 Leopard Sharks (male n=6, female n=7) tagged with coded acoustic transmitters were monitored from March 14, 2013 to March 9, 2014 using moored receivers in Elkhorn Slough, CA. Movement patterns were compared by region within Elkhorn Slough and related to environmental variables. Tagged individuals of both sexes spent the majority of time in the middle section of Elkhorn Slough, though females were more frequently present early in the day and uncommonly recorded after noon; males consistently used the middle section of Elkhorn Slough throughout the day. The monthly number of hours male Leopard Sharks were detected in the study site was positively correlated with water temperature and female Leopard Shark detected hours were negatively correlated with dissolved oxygen concentration. Differences in frequency of detection at temperatures ranging from 13°-16° C were dependent on sex and region of Elkhorn Slough.

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