Research Document - 2016/075

Review of Winter Skate (Leucoraja ocellata) in the Northern Gulf of St. Lawrence in Support of a Recovery Potential Assessment

By Johanne Gauthier and Claude Nozères

Abstract

In 2005, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) first assessed Winter Skate (Leucoraja ocellata) of the northern Gulf of St. Lawrence (nGSL) as data-deficient. In April 2015, COSEWIC re-assessed Winter Skate and revised population structure by grouping nGSL and southern Gulf of St. Lawrence (sGSL) fish in a new designatable unit (DU), the Gulf of St. Lawrence DU with the status endangered. This re-definition of the DU was mainly based on the spatial distribution of Winter Skate and potential heritable traits that indicate significant adaptations. Compared to other populations, Winter Skate in the sGSL mature at a much smaller size and earlier age, have a much shorter maximum length, occur in shallower and warmer water in summer, and differ in morphological characters (teeth and jaws) related to feeding.

This document revisited available data in the nGSL to confirm records of Winter Skate, and to seek information to help determine if these skates exhibit characteristics similar to the sGSL type, i.e. early-maturing, found in warm and shallow waters in summer. 

Records of Winter Skate in the nGSL were reviewed using:

1. available survey photos,
2. survey catches with depth and geographic location data, and
3. individual weight-length data.

Extensive sampling of the nGSL indicates that Winter Skate occur very rarely in this region. The very limited number of individuals (n = 3) for which biological information and maturity data are available would indicate that the early-maturing sGSL Winter Skate type can be found in the St. Lawrence Estuary, NAFO Division 4T, and that the late-maturing type is present on the west coast of Newfoundland and in the Bonne Bay fjord, Division 4R.  The confirmed Winter Skate of the early-maturing type in the Estuary may be a vagrant individual caught outside of the normal range of sGSL Winter Skate.

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