Proceedings 2017/010
Proceedings of the Regional Framework Discussion on Stock Substructure of Northwest Atlantic Fisheries Organization (NAFO) Divisions 3NOPs4VWX5Zc Atlantic Halibut, Hippoglossus hippoglossus (Scotian Shelf and Southern Grand Banks); March 9-11, 2016
Chairperson: Martha Krohn
Editor: Kristian Curran
Summary
Atlantic Halibut (Hippoglossus hippoglossus) is a large and long-lived flatfish. It ranges widely in the Northwest Atlantic. In Canada, Atlantic Halibut has been assessed as two regional-scale stocks since 1988, yet the knowledge about its basic ecology is limited. Population structure, migration routes, timing and location of spawning are all unknown. Currently, the management units are the Northwest Atlantic Fisheries Organization (NAFO) Divisions 3NOPs4VWX5Zc (Scotian Shelf and Southern Grand Banks) and NAFO Divisions 4RTS (Gulf of St, Lawrence). The management units were defined by tagging data that showed some Halibut travelled long distances but that mixing between these two areas was low. Recent research investigated Halibut that span the border separating the United States of America (US) and Canada and showed that, from 1965 to 2014, juvenile abundance was, on average, five times greater on the Canadian side of the Hague Line (the nautical international border between US and Canadian waters).
The median per cent of occupied sets on the Canadian side was about 4 times greater than in US waters 2.5%), despite the availability of “suitable” habitat on the US side. There was also evidence to suggest that Atlantic Halibut in US and Canadian waters are connected through the Bay of Fundy and eastern Gulf of Maine. The available evidence suggested that Halibut have not re-established in the US after historical overfishing and that Halibut exhibit a finer spatial structure than assumed in the stock assessment. Subsequent research has identified high density areas of juvenile Halibut that may be indicative of 3NOPs4VWX5Zc Atlantic Halibut stock substructure on the Scotian Shelf and Southern Grand Banks. A better understanding of Halibut substructure and connectivity between high density areas could provide an improved basis for sustainable management. Multiple lines of evidence are necessary to evaluate stock structure and the appropriate management strategies in the face of this new data synthesis.
Recovery of the stock has allowed for increased access by Canadian domestic and international fishing fleets. Continued sustainable exploitation of this resource would benefit from a collaborative approach between the three coastal states that have a primary interest in the stock: Canada; US; and France. As part of the Regional Peer Review process, a meeting was held on March 9-11, 2016, at the Delta Barrington Hotel in Halifax, Nova Scotia, to review a science framework that could be used to support development of a Halibut research program and a common understanding of stock structure among the three coastal states. The discussion was guided by a series of presentations. This Proceedings document constitutes a record of meeting discussions, recommendations, and conclusions, and any statements within should not be attributed as being consensus-based. A Science Advisory Report was not a product of the meeting.
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