Publication Date

Fall 2019

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Studies

Advisor

Lynne . Trulio

Keywords

elasmobranch, Hydrology, Leopard Shark, Salinity, San Francisco Bay Estuary, Triakis semifasciata

Subject Areas

Environmental studies; Biostatistics

Abstract

The San Francisco Estuary (the Estuary) supports a diversity of native marine species, including the leopard shark (Triakis semifasciata). As the human population has increased in the Bay Area, elasmobranchs have simultaneously been subjected to habitat loss and changes in hydrology. On a large scale, global climate change is also affecting the Estuary's water quality. There is little research on the long-term population size of leopard sharks in the Estuary. Leopard shark catch data collected by the Marine Science Institute (MSI) and water quality data from the United States Geological Survey (USGS) from 1998 to 2017 were analyzed to assess long-term trends in leopard shark abundance, as well as the hydrological conditions in the southern portion of the Estuary that might be contributing to those trends. Results from this study indicated that the annual abundance of leopard sharks in this region has remained relatively stable over the study period despite interannual variability in CPUE and significant changes in fundamental abiotic estuarine elements. Low salinity was determined to influence leopard shark abundance when analyzed during the months of April to August. Further analyses on the status of leopard sharks as conditions related to climate change continue to challenge elasmobranch species could help managers protect the estuary environment.

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