University Events

Description: The School for Marine Science and Technology
Department of Fisheries Oceanography
PhD Proposal Defense

"Combining Mark Recapture Techniques With New Technology to
Improve Fish Population Estimates"

By
Nicholas M. Calabrese

Graduate Advisor:
Dr. Kevin Stokesbury

Committee Members:
Dr. Steven Cadrin University of Massachusetts Dartmouth
Dr. Pingguo He, University of Massachusetts Dartmouth
Dr. Michael Stokesbury, Acadia University, Nova Scotia
Dr. Anna Mercer, Northeast Fisheries Science Center, Woods Hole, MA

Friday, January 15, 2021
1:00 pm
via Zoom

Abstract:
Fisheries independent surveys provide stock assessment scientists with a time-series of relative abundance, typically catch per unit effort, that indicates trends in stock size through the years (Gunderson 1993). The SMAST video trawl survey is a fisheries independent survey that uses a camera placed in the codend of a trawl net to identify and enumerate groundfish (Stokesbury et al. 2018). This survey began in 2016 and lacks a long time-series instead, the area-swept by the trawl is used to estimate the absolute abundance in the survey area. This estimate assumes that all fish within the path of the trawl are captured (100% efficiency), which makes it the most conservative estimate of abundance from the survey catches. The goal of this project is to estimate the catchability of cod in the SMAST video trawl net, which relates catch per unit effort to absolute abundance. This would allow
us to make more accurate estimates of abundance to help inform fisheries managers.
To accomplish this goal, we will use a passive integrated transponder (PIT) tag detection system located in the codend of the net to detect previously tagged fish in a mark-recapture experiment. The population estimate from the mark-recapture experiment will be used with the catch per unit effort of the trawl to calculate efficiency. The first chapter of this project will focus on evaluating the assumptions of different mark-recapture models to identify the best fit. The second chapter will be designing and testing a codend PIT tag detection system to
evaluate its efficiency in reading tags. In the third chapter, we will complete the mark-recapture experiment and estimate the catchability of cod in our survey. Finally, in the fourth chapter we put it all together with an expanded version of our survey to estimate the abundance and biomass of cod in the Western Gulf of Maine.
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For additional information, please contact Sue Silva at s1silva@umassd.edu