Winter Skate (Leucoraja Ocellata)
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- List of Figures
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Existing Protection or Other Status
- Summary of Status Report
- Technical Summary
- Acknowledgements, Authorities Contacted, and Information Sources
- Biographical Summary of Report Writer
Winter skate (Leucoraja ocellata Mitchill 1815), also known as the big or eyed skate, are recognized by a flattened disc shape, greatly enlarged wing-like fins, and long tail. The upper surface is usually light to dark brown with a large white eyespot near the rear corner of the pectoral fins, which helps distinguish them from other species of skate.
Winter skate are endemic to the Northwest Atlantic and are found from the northern Gulf of St. Lawrence and southern Newfoundland to Cape Hatteras, North Carolina. In Canadian waters, skate are concentrated in 3 areas: southern Gulf of St. Lawrence, eastern Scotian Shelf, and the Canadian portion of Georges Bank. Winter skate have been assessed as four Designatable Units: Southern Gulf of St. Lawrence population, Eastern Scotian Shelf population, Georges Bank-Western Scotian Shelf-Bay of Fundy population, and Northern Gulf-Newfoundland population.
The winter skate is a bottom-dwelling species, usually found on sand and gravel. They occur at depths of up to 371 m, but are most common at depths less than 111 m. Most are caught in waters ranging between 5 and 9°C (range: -1.2 to 19°C).
Very little is known about the biology of winter skate. They grow slowly and reach sexual maturity between 7 and13 years at lengths estimated to range between 50 cm and 75 cm. Maximum age has been estimated to be as high as 30 years. Generation time is estimated to be between 17 and 22 years. Fecundity ranges between 6 and 50 eggs. Spawning has been reported to occur in late summer/early autumn. The diet consists mainly of rock crab and squid, as well as worms, amphipods, shrimp, clams and small fish.
Population Sizes and Trends
Population size and trends in abundance can be estimated from fisheries-independent surveys. Estimates of minimum total abundance are 100 000 for the Southern Gulf population, 750 000 for the Eastern Scotian Shelf population, and 1.7 million for the Georges Bank-Western Scotian Shelf-Bay of Fundy population; abundance has not been estimated for the Northern Gulf-Newfoundland population. Since the early 1970s, mature winter skate are estimated to have declined 98% in the Southern Gulf and more than 90% on Eastern Scotian Shelf. There is no discernible trend in the abundance of mature skate in the Georges Bank-Western Scotian Shelf-Bay of Fundy population. Abundance trend information for the Northern Gulf-Newfoundland population is unavailable because of the rarity of the species in these waters. Winter skate on the U.S. portion of Georges Bank, although not defined as being overfished, are at low levels relative to their abundance in the mid-1980s.
Limiting Factors and Threats
Narrow latitudinal ranges and a high degree of endemism have been documented for the skate family worldwide. Of 58 documented marine fish extirpations, 13 have been experienced by members of the skate family (Rajidae). Winter skate possess life history characteristics that increase vulnerability to exploitation, that reduce rate of recovery, and that increase risk of extinction. These characteristics include delayed age at maturity, large size at birth, long generation time, low fecundity, and consequently slow population growth rate. In Canadian waters, winter skate are subject to capture as bycatch in fisheries for other groundfish species (notably flatfishes) and, on Georges Bank, for scallops. The Eastern Scotian Shelf population is subjected to a small, directed fishery.
Special Significance of the Species
Winter skate are endemic to the western North Atlantic with a considerable portion of their range in Canadian waters. They are among the most ancient of extant species of vertebrates. The species has, at various times, supported a directed fishery.
Existing Protection or Other Status Designations
In Canadian waters, commercial catches are regulated by the Department of Fisheries and Oceans. All populations in Canadian waters are subject to bycatch. The only directed fishery in Canadian waters is a limited one that exists on the eastern Scotian Shelf, where annual Total Allowable Catches (TACs) have declined from 2000t in 1994 to 200t, a TAC set initially in 2002. Winter skate have no status under IUCN.
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