An Analysis of Gulf of Maine Cod Metapopulation Structure and Localized Stability, with Application to Area-Based Fisheries Management

• Main Author: Olson, Derek
• Format: Text
• Language: unknown
• Published: DigitalCommons@UMaine 2016
• Subjects: groundfish; early warning signals; depensation; Allee effect; stock structure; local management; Marine Biology; Natural Resources Management and Policy; atlantic cod; Gadus morhua
• Online Access: https://digitalcommons.library.umaine.edu/etd/2582; https://digitalcommons.library.umaine.edu/context/etd/article/3610/viewcontent/Derek_Olson_Thesis_Corrected.pdf

The complex metapopulation structure of groundfish stocks in the Gulf of Maine, particularly Atlantic cod (Gadus morhua), is largely ignored under the current system of broad-scale stock assessment and management. This mismatch of biological and administrative scales has contributed to severe overall stock decline and localized serial depletion of Gulf of Maine cod. Such chronic management failure has led to growing calls for a more area-based, finer-scale approach to managing groundfish in the Gulf of Maine. A primary difficulty hindering the development of finer-scale groundfish management has been the challenge of estimating fishing mortality upon local stock components. However, generic system dynamics models may permit early identification of stock components being pushed toward instability by excessive fishing pressure. Interpolation of existing fishery-independent survey data within approximate subpopulation boundaries permits the construction of estimated abundance indices for metapopulation components. This study utilizes a model-based approach to classify these indices into risk categories based on the likelihood that they may be trending toward more unstable dynamics. Such an approach offers a potential solution to the problems of limited data and logistical impracticality that prevent the use of analytical assessment models at finer spatial scales.