Date of Award

12-2014

Level of Access

Campus-Only Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Marine Biology

Advisor

Yong Chen

Second Committee Member

James Wilson

Third Committee Member

Deborah Hart

Abstract

Sustainable management of fishery resources is typically required by law. In order for management to be successful, the regulatory authority must understand the states and dynamics of fish populations and fishing fleets. Armed with this knowledge, managers can adjust the level of fishing mortality so that populations are harvested sustainably.

There is considerable contrast in knowledge about sea scallops (Placopecten magellanicus) in the two regions in the northeast US where they are fished. Stock dynamics in the Gulf of Maine have not been well-studied, but the populations on Georges Bank and in the mid-Atlantic are among the most data-rich species in the US. The purpose of this study is to address knowledge gaps in both these regions.

A separate stock area was created for Gulf of Maine scallops in 2008, to be managed by a total allowable catch. However, little information was available to determine this limit. Surveys were conducted in 2009 and 2012 and fishable biomass was estimated for both these years to help develop an allowable catch for the Gulf of Maine. In addition, during this survey scallop shells were collected and analysis of growth increments showed that scallops in different areas of the Gulf of Maine grow at different rates.

A standard assumption throughout the history of fisheries assessment has been the "dynamic pool," meaning all individuals have an equal probability of capture by the fleet. Fisheries scientists have known this to be an over-simplification; still there are few spatially- integrated stock assessments. Using a Yield per Recruit and a catch-at-size model, the potential consequences of assuming a dynamic pool when capture probability is not equal across the stock are examined. The results show that when a stock assessment model erroneously assumes equal capture probability, estimates from the model can be biased.

The results provided by this research increase the breadth of knowledge about sea scallop population dynamics and modeling, and can contribute to sustainable management of this species within the study area.

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