Date of Award

12-2020

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Marine Sciences and Technology

First Advisor

John Mandelman

Second Advisor

Robert Chen

Third Advisor

Jeff Kneebone

Abstract

Fish have been an important food resource for humans throughout history, but with growing populations increasing the demand for this resource, many fish stocks have become overfished. In response, management has traditionally addressed overfishing by establishing regulations that reduce the directed fishing mortality associated with harvesting. However, these practices often do not take into account the mortality associated with fish that are incidentally captured and discarded (as bycatch). This discard mortality (DM) can represent a potentially large source of removals for species that are particularly susceptible to the stressors of capture-and-handling and/or discarded at high rates. It is therefore vital to understand overall DM in a fishery and the factors associated with capture-and-handling driving mortality. But this information can be very challenging to collect, with many species/fisheries having yet to be addressed. In light of these difficulties, my dissertation aimed to develop novel tools and techniques that improve our ability to evaluate and/or reduce the impacts associated with fisheries-interactions. In particular, this included (1) the development of a technique that addresses capture behavior as an underlying driver of mortality, (2) a novel application of electronic tags to better deduce fate in a family of frequently discarded fish, and (3) a new tool for forecasting where fisheries-interactions (i.e., incidental capture) are most likely to occur in both time and space. The information provided by these tools and techniques will help inform stock assessments and bycatch mitigation strategies, which in turn will help to promote the sustainability of bycatch species. Moreover, two species of elasmobranch [thorny skate (Amblyraja radiata) and oceanic whitetip shark (Carcharhinus longimanus)] were used as case study species in this dissertation. Both have been heavily overfished, but the impact of capture-and-handling remains poorly understood for each species. Thus, my dissertation contributes critical capture-related information for thorny skate and oceanic whitetip shark, which could aid in the development of future mitigation strategies to promote their recovery.

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