Date of Award

2017

Document Type

Honors Thesis (Open Access)

Department

Colby College. Environmental Studies Program

Advisor(s)

William McDowell

Second Advisor

Caitlin Cleaver

Third Advisor

Loren McClenachan

Abstract

The Midcoast Maine Collaborative Scallop Project was established in 2013 by fishers, scientists, and policy makers to determine if a small-scale closure area could restore the local Atlantic sea scallop (Placopecten magellanicus) population to an area in coastal Maine that previously supported high scallop densities. These stakeholders established a three by one mile closure area in the Lower Muscle Ridge Channel to assess the response of the adult and larval scallop populations. Understanding the larval dynamics in a closure area is key to evaluating the recovery potential of the population and for future population stock levels. This study seeks to determine if larval abundance 1) has changed over the three-year closure period and 2) varies inside the closure area as compared to adjacent fished areas. To gauge larval abundance, 36 spat bags were deployed to collect scallop larvae over the three-year study. A before-after-control-impact (BACI) design was used to determine if recruitment increased within the closure using 2013 data for a baseline before the closure was implemented and to control for initial differences from different areas. In 2014 and 2015, higher abundance of larval scallops were recorded both inside and outside of the closure area as compared to 2013 abundance (p=0.010 and p=0.011). There was no significant difference in abundance inside compared to outside the closure (p=0.30), suggesting that scallop spat is increasing to the system as whole, not just within the closure area. This increase is a potential first sign of recovery for the resident scallop population, and indicative of increased adult populations and larger size class scallops. Early data analysis of adult populations shows increased frequency of juvenile size-class scallops in 2016, suggesting that the increased spat abundance seen in 2014 survived to juvenile age, an additional early sign of recovery showing success of the closure area to rebuild adult populations in the area.

Keywords

Scallops, Fishery Management, Placopecten magellanicus, Gulf of Maine, Fishery Closures, Larval Abundance

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