Date of Award

12-2020

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Marine Sciences and Technology

First Advisor

John W. Mandelman

Second Advisor

Robert F. Chen

Third Advisor

Andy J. Danlychuk

Abstract

Recreational fishing (i.e., angling), a popular leisure activity that provides socio-economic benefits to human societies around the world, can represent a significant source of fishing mortality and impact fish populations and marine ecosystems. Although fish are often released by recreational anglers to reduce fishing mortality rates, the efficacy of discarding fish is often criticized given that fish can die from the factors experienced during the capture, handling, and release process (i.e., discard mortality). Despite this recognition, the rate at which fish suffer discard mortality in specific commercial and recreational fisheries is often unknown and difficult to obtain due to logistical constraints, representing a global concern for fisheries management and sustainability. Such is the case in the Gulf of Maine multispecies recreational fishery for groundfish, specifically Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), and cusk (Brosme brosme), where, until recently, discard mortality concerns were frequently identified as key sources of uncertainty in stock assessments and management decisions.

To this end, my dissertation presents results from three field-based studies and one qualitative survey to address discard mortality knowledge gaps in this fishery. With the use of electronic tagging and survival analyses, I empirically-derived a discard mortality rate of haddock representative of the fishery and generate responsible fishing practices to reduce such mortality risk. Similarly, I used a field-based tagging approach to determine cusk discard mortality, both in its current state in the fishery and with the use of barotrauma mitigations methods (i.e., descending devices). Given the critically-depleted state of the Atlantic cod stock, I conducted a large-scale sampling effort to identify an ideal set of terminal tackle that anglers could use to sustainably target haddock over Atlantic cod while reducing discard mortality in both species. Finally, because managing fish involves managing people and their expectations, I surveyed anglers who target groundfish to determine if their angling behavior would influence their willingness to adopt responsible fishing practices from previous chapters and what channels they use to access angling information. Taken together, my results highlight the socio-ecological complexity of discard mortality and its implications on the current and future sustainability of this recreational fishery.

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