Population connectivity and its application to marine protected area effectiveness in a sub-Arctic coastal ecosystem

Morris, Corey John (2013) Population connectivity and its application to marine protected area effectiveness in a sub-Arctic coastal ecosystem. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Atlantic cod (Gadus morhua) in Gilbert Bay provides an opportunity to better understand the potential effectiveness of a Marine Protected Area (MPA) in providing protection for a specific population, including the roles that oceanography and behaviour may play in population connectivity. This thesis uses long-term monitoring and research (1998-2011) through mark-recapture tagging, oceanographic sampling, ichthyoplankton tows, and acoustic telemetry tracking to describe demographic trends and population connectivity of the Gilbert Bay Atlantic cod population in southeastern Labrador, Canada. The population declined considerably after Gilbert Bay became a MPA, presumably as a direct result of legal fishing activities outside MPA boundaries. Therefore connectivity research was undertaken to investigate population dynamics and infer strategies to Improve MPA effectiveness. The locally adapted timing and location of spawning strongly influences the population's localized connectivity, resulting in egg retention at the spawning area. Tagging showed high site fidelity in juvenile and adult cod and that migratory adults exhibit strong homing behavior. Migratory adults move up to 40 km rom the population's core area, but return to that core area to overwinter and spawn. Transplant experiments demonstrated the importance of prior experience for successful homing. Fish displaced outside their known or assumed home range displayed very low homing success compared to those displaced to areas within their home range. Adolescent and adult Atlantic cod migrated briefly from the head of the bay towards coastal areas for summer feeding, which increased susceptibility to fishing in areas outside the MPA. However, most ultrasonically tagged fish moved less than 10 km outside MPA boundaries. This new information on the timing and locations of fish movement can improve MPA effectiveness by identifying times and locations when a portion of the protected population moves away from the MPA and becomes vulnerable. Such knowledge can facilitate adaptive management and improved co-operation between MPA stakeholders and fisheries managers.

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