Research Document - 2010/043

Incidental catch amounts and potential post-release survival of winter skate (Leucoraja ocellata) captured in the scallop dredge fishery in the southern Gulf of St. Lawrence (2006-2008)

By H.P. Benoît, D.P. Swain, M. Niles, S. LeBlanc and
L-A. Davidson

Abstract

Winter skate (Leucoraja ocellata) in the southern Gulf of St. Lawrence were designated as endangered by the Committee on the Status of Endangered Wildlife in Canada in May 2005. A recovery potential assessment undertaken that year concluded that high adult mortality was responsible for the declines in abundance. There has been no directed fishery for winter skate in the area, and estimated bycatch in groundfish and shrimp fisheries was very low. However, the impact of discarding in the southern Gulf of St. Lawrence scallop (Placopecten magellanicus) fishery on winter skate mortality could not be quantified at the time due to a lack of information on incidental catches. Because there is considerable spatial-temporal overlap between the scallop fishery and the distribution of winter skate, there is potential for elevated fishing-induced mortality. In this report we present results from at-sea sampling of fish bycatch in the southern Gulf scallop fishery undertaken in 2006-2008, including the number, size, location of capture and post-discard survival potential of incidentally caught winter skate. Most winter skate captured in the scallop fishery were released alive and in very good condition, suggesting that post-release survival is high. Based on observed catches and estimates of discard survival, the estimated mean annual exploitation rate (percentage of the population killed) over the study period is 0.14% for juvenile winter skate and 0.06% for adults. This fishing-induced mortality is very small compared to mortality from other sources.

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