Winter Skate

Leucoraja ocellata

Description

The winter skate has a depressed body, a slender tail, a disc about 1.2 to 1.3 x as broad as it is long, a snout with an anterior angle of about 130° or more, and a tail with narrow lateral folds from the posterior axils of the pelvic fins all the way to the end. The mouth is gently arched, with 63 or more rows of teeth in the upper jaw, but varying substantially with the size of the fish. In females, the teeth are blunt, whereas in males, the teeth have distinctive, high conical cusps. The upper surface of the disc is rough with numerous thorn-like spines decreasing in number as the fish matures. Specifically, the winter skate has 2 to 3 irregular rows of spines on either side of the midline of the disc extending onto the anterior part of tail; an irregular triangular group of spines in the neck and shoulder region; a few spines behind, in front, and along the inner margin of each orbit and several spines in between. Young winter skate have a row of large median spines along the disc and tail that are lost in individuals greater than about 50.8cm TL. The lower surface is smooth, with the exception of a few spines in the snout region. The winter skate has two dorsal fins with joined bases located near the end of tail; a very small caudal fin; and bi-lobed pelvics overlapped by the pectorals. Colouration is light brown dorsally with varying numbers of ovoid, blackish spots, and white ventrally, sometimes with irregular brownish blotches on the posterior portion of the disc and tail. There are often 1 to 4 dark spots with white margins (called 'eye' spots) on the upper surface near the posterior portion of the pectorals. Winter skate are difficult to distinguish from little skate (Leucoraja erinacea), particularly at sizes below 30 to 35 cm TL. As such, examination of a combination of characters is necessary to differentiate between the two species. In winter skate, the mouth is wider and less arched than in the little skate. Female little skate have small pelvic spines very near the cloaca that are rough to the touch, whereas the pelvic spines in female winter skate are more toward the outside edges of the pelvic fins. Male winter skate have pelvic spines but male little skate do not. Tooth counts have also been used to differentiate the two species. Winter skate have 63 or more rows of teeth in the upper jaw, whereas little skate have only 30-62 rows. However, tooth count in both species varies considerably with size of the fish, making this a difficult means of distinguishing between the species. Genetic analyses are the best way to identify little and winter skate below 30 - 35 cm TL. Specifically, a polymerase chain reaction - restriction fragment length polymorphism (PCR - RFLP) assay is used to genetically differentiate between species.

Size

The winter skate is one of the larger species of skate in Atlantic Canada waters, reaching a maximum size of about 109 cm TL. Maximum size appears to vary slightly with geographic region (see Life History section).

Range

The winter skate is restricted to the northwest Atlantic Ocean. The northernmost limit of the winter skate range is the south coast of NewFoundland, from which it ranges south into the Gulf of St Lawrence, along the Scotian Shelf, the Bay of Fundy , and Georges Bank, southward to Cape Hatteras. The winter skate has a slightly wider distribution than the little skate (Leucoraja erinacea), occurring in the Gulf of St. Lawrence and on the northern parts of the Scotian Shelf where the little skate is not found.

Habitat

The winter skate is a benthic species living over sand or gravel bottoms, usually in depths less than 111m; however, it has been captured at depth of 371 m in the Gulf of St. Lawrence. The total temperature range in which winter skate have been caught is -1.2 - 15°C. In the southern parts of its range such as the Bay of Fundy , the winter skate appears to move shoreward in autumn and offshore in the summer, suggesting a preference for cooler temperatures (i.e. "winter periodic"). In contract, research vessel (RV) surveys on the eastern Scotian Shelf suggest this species does not more inshore in the winter. Instead, based on anecdotal reports from the fishing industry, winter skate appear to move onto the banks (i.e. Sable Island Bank, Banquereau Bank) in the summer and into deeper waters in the winter.

Life History

Studies on age, growth and maturity in winter skate have demonstrated that this species is slow-growing, late-maturing and long-lived, and is therefore vulnerable to decline due to over-exploitation. Of particular concern is the late age at maturity reached by females relative to the maximum observed age, leaving very few total lifetime spawning episodes for each individual female. A recent study on the vulnerability of NW Atlantic skates on the eastern Scotian Shelf (ESS) carried out here at the Bedford Institute of Oceanography found that out of the four most commonly occurring species on the ESS (i.e. winter, little, thorny and smooth skate), winter skate has the lowest intrinsic rate of population increase and therefore can sustain only very low levels of fishing pressure. For more information on how life history characteristics are determined in NW Atlantic skate, go to the Skate Research section of this website or refer to the references listed in the table below. For more information on the status of winter skate in Canadian waters, go to the Skate Conservation section of this website.

Diet

Winter skate eat mostly amphipods and polychaetes, but also consume fishes, decapods, isopods, and bivalves. Fishes (such as sand lance) are of greater importance in large individuals, and have been found in high volume in the stomachs of individuals captured in summer. Dietary preference or opportunistic feeding (i.e. consumption of different proportions of the same prey) may allow the winter skate to avoid direct food competition with the sympatric little skate (Leucoraja erinacea), with the winter skate consuming relatively more infaunal species.

Reproduction

Winter skate from the Gulf of Maine exhibit a partially defined reproductive cycle with a peak in reproductive activity in July, and maximum egg-case production in September, October and November. Males produce mature sperm throughout the year, and reproductively capable females are found during most months of the year. On the eastern Scotian Shelf, seasonality in the breeding cycle of winter skate is difficult to determine due to a lack of mature female winter skate, possibly due to the collapse of the population in the area. However, anecdotal observations suggest that egg-deposition off Nova Scotia reaches a maximum from late summer through the fall. Young winter skate are approximately 11.2 to 12.7 cm long when they emerge from the egg case. For more information on how reproductive cycle is determine in NW Atlantic skate, go to the Reproduction Research section of this website. For a look at the egg capsules of the winter skate, click on the link Identification of NW Atlantic Skate Egg Capsules.

Interaction with people

Until recently, winter skate were of little economic importance in Atlantic Canada. However, following declines in traditional fishfin stocks, the Canadian Department of Fisheries and Oceans established a directed fishery for winter skate mainly on the eastern Scotian Shelf (ESS). This fishery has since shut down due to a listing of the winter skate on the ESS as threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). Nevertheless, winter skate continue to be caught incidentally as bycatch in Canadian waters. For more information go to the Skate Fisheries and Skate Conservation sections of this website. In New England, winter skate are used for human consumption and as coarse fish in the manufacture of fish meal and pet food. Assessment studies in the northeastern USA suggest that the winter skate may be over-exploited.

Common Names

Also called "big skate" or "eyed skate".