Defense Date

7-27-2017

Document Type

Capstone

Degree Name

M.S. Marine Biology

First Advisor

Mahmood Shivji

Second Advisor

Bradley Wetherbee

Abstract

Many shark species have global distributions and are caught incidentally in different types of fisheries. Over the last two decades, shark populations have declined tremendously, with one of the leading causes of this decline bycatch in primarily teleost fisheries. Bycatch occurs throughout the world’s fisheries, but is not well documented in terms of species composition and numbers of each species captured. Information on shark bycatch is spread through the primary and grey literature, but has not been compiled in summary to date. The goal of my capstone is to present global shark bycatch data and provide a comparative review to determine fishery types that affect shark populations and identify shark species at risk as a result of bycatch. Longline fisheries caught a larger variety of shark species, and the post-release mortality was generally low. In contrast, trawl fisheries caught mostly the same few species, but post-release mortality was extremely high. Blue sharks (Prionace glauca), silky sharks (Carcharhinus falciformis), and spiny dogfish (Squalus acanthias) were caught most often in trawl fisheries, and in large numbers that likely adds to risk of overexploitation of their populations. This literature review revealed a severe lack of standardization in bycatch data reporting by different fishing nations, and in documents prepared by management agencies and scientists, including the definition of bycatch used and the way it was recorded. Establishing a universal definition of bycatch and standardizing its reporting would vastly improve ability to assess the scale and composition of shark bycatch and its impacts on shark populations. Systematic and standardized accounting of shark bycatch would provide information helpful for collaboration among regulatory agencies. Rather than simply document bycatch, a number of fishing gear alterations show promise for bycatch reduction and are worthy of integration into fisheries by managers. Additional important steps that can improve bycatch assessment is increased observer coverage in fisheries, marine protected areas, and making bycatch data public.

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