Research Document - 2011/030

Pre-COSEWIC Review of Atlantic Halibut (Hippoglossus hippoglossus) on the Scotian Shelf and Southern Grand Banks (Divs. 3NOPs4VWX5Zc), Gulf of St. Lawrence (Divs. 4RST), Newfoundland and Labrador, and Central and Arctic

By M.K. Trzcinski, C. den Heyer, S. Armsworthy, S. Whoriskey, D. Archambault, M. Treble, M. Simpson, and J. Mossman

Abstract

All data relevant to the status of the Atlantic halibut, (Hippoglossus hippoglossus), in Canadian waters were gathered from four DFO regions: Maritimes, Gulf, Newfoundland, and Quebec with the objective of providing information to the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) for their review. In particular, data on life history, habitat, landings, surveys, and bycatch were collated. Correction factors for gear changes in the groundfish surveys were not applied and the results on distribution and trends need to be interpreted with caution. This assumption is probably adequate for most regions as correction factors for flatfish were small, but the gear change to a Campelen trawl in Newfoundland could have a large effect and is unquantified. Halibut continue to be rare on Georges Bank and in the eastern Arctic, their distribution has expanded in the Gulf, but their distribution on the Scotian Shelf and the southern Grand Banks has not changed appreciably. Little is known about the timing and location of halibut spawning, and the location and movement of eggs and larvae. A simple linear regression was fit to the groundfish survey data in each region over the entire survey time period. No trends were calculated for the southern Grand Banks because gear changes were large and no correction factor has been estimated. There was no change in halibut catch rates on the Scotian Shelf and significant increases in the northern and southern Gulf of St. Lawrence. Trends, calculated as the percent difference between the mean catch rate in the first five years in the time series and the last five years of the survey were increasing on the Scotian Shelf (74%) and the northern and southern Gulf of St. Lawrence (>200%).

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