Research Document - 2003/028
Distribution and abundance of winter skate, Leucoraja ocellata, in the Canadian Atlantic
By Simon, J.E., Harris, L.E. and Johnston, T.L.
Abstract
Data derived from four principal sources in the Canadian Atlantic zone, spanning several decades, were examined for the occurrence of winter skate. The data reviewed included standardized research vessel (RV) surveys conducted by Fisheries and Oceans Canada (DFO), non-standard research vessel surveys and recent industry/science surveys. Some persistent areas of concentration were evident, notably Georges Bank and the eastern Scotian Shelf. Secondary concentrations are found in the Bay of Fundy, the Laurentian Channel, inshore waters of 4T and the southern flanks of the Grand Banks. Winter skate are not and have never been common in most of the Newfoundland area. This species appears to be adequately surveyed in the zone. Winter skate occur in areas deeper than the regular groundfish surveys but not in any great quantities. Given the distribution in 4T it is more likely that winter skate will be inshore of the areas surveyed.
Limited information exists on the biology of winter skate, however recent studies have shown that length at 50% maturity is 75 cm for females in Div. 4VsW. Given that no individuals greater than 70cm have been caught in Div. 4T during the 32 years of their survey it is unlikely that this value will hold for the entire range of the species.
In general, winter skates abundance in the southern part of the range has remained stable, while further north declines have been evident, especially larger individuals. Winter skate are the 3rd, 22nd and 13th most common species in the Georges, summer and spring RV surveys respectively. Overall the research vessel surveys have estimated the minimum total number of individuals to average over 3 million individuals in Div. 4TVWX. The decadal averages in Div. 4TVWX are all very close to 3 million, though the estimate in the last 5 years has been close to 1.5 million individuals. In the Canadian part of Div. 5Z the minimum average estimate is 1.8 million individuals. A skate industry/science survey in Div. 4VsW yielded biomass estimates that were 6-12 times greater than the summer RV survey in the same area, suggesting that these population numbers are most likely an underestimate of the population.
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