Research Document - 2015/042

Catch of non-targeted species in the Scotian Shelf and Southern Grand Banks (NAFO Divisions 3NOPs4VWX5Z) Atlantic Halibut Longline Fishery

By D. Themelis and C. den Heyer

Abstract

Species composition of catches by the commercial longline fishery targeting Atlantic Halibut (Hippoglossus hippoglossus) on the Scotian Shelf and Southern Grand Banks (Northwest Atlantic Fisheries Organization (NAFO) Divisions 3NOPs4VWX5Zc) were characterized using at-sea observations from the commercial fishery and Commercial Index phase of the joint Fisheries and Oceans Canada (DFO)-Industry Halibut Survey. Commercial longline sets reporting hook sizes 14-16 are proposed as a method of distinguishing fishing targeting halibut from sets directed for other groundfish species. Observer coverage ranges from 4-13% in NAFO Area 4 and 15-87% in NAFO Area 3 and does not match well with the seasonal distribution of the fishery. Fishing during the summer months has higher observer coverage because of the Commercial Index, but there is low coverage in the months during which highest landings occur: in NAFO Divisions 3NOPs from November to December, in NAFO Divisions 4VW from January to May, and in NAFO Division 4X from August to October. The halibut-directed longline fishery keeps the majority of its catch (70-85% by weight), with the majority of the retained catch being halibut. Species composition of observed catches varies geographically and seasonally. The main retained non-target species are Atlantic Cod, White Hake and Cusk. The main non-retained species are Barndoor Skate and other skates. Given the geographic and seasonal changes in relative abundance and catchability of halibut and other species, total bycatch is estimated by scaling observed catches summed by area and season by the proportion of halibut landed during halibut-directed fishing. Notably, while the proportion of non-target species in the catch of the halibut-directed longline fishery has been decreasing, with increasing halibut total allowable catch, the total catch of non-target species could increase.

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