Conservation Genetics of Sharks

Abstract

In this dissertation I apply molecular techniques to assist in fisheries management decisions for pelagic sharks and explore the global stock structure of one of them. Additionally, I developed and tested a method for species identification from trace DNA left behind after shark bites. Chapter 1 is an introduction to the broader topic of pelagic shark management and specific issues for silky sharks. Chapter 2 compares traditional genetics methods used for managing elasmobranch populations with a high-throughput method known as pool-seq. Results from this chapter highlighted pool-seq as superior at detecting genetic stock structure between populations of silky sharks in the Atlantic where previous Sanger sequencing of mtDNA found no differences. Additionally, this chapter shows sequencing costs for pool-seq become cheaper as sample sizes increase compared to Sanger sequencing of mtDNA. Chapter 3 illustrates the global stock structure of the silky shark using genomic approaches and shows a much higher degree of genetic stock structure than previously documented. Silky sharks have population structure more similar to that of coastal sharks rather than true pelagic migrants. These data indicate that they don’t roam around the oceans as much as previously thought. Additional support for this hypothesis is presented as well as management implication. Chapter 4 highlights methods we developed for identifying species responsible for shark bites on surf boards and wet suits. These methods were utilized on 32 controlled shark bites on devices around Australia and Hawai’i with 31 yielding genetic sequences appropriate for species identification. Chapter 5 is a conclusion with suggestions for future research.