Smooth Skate (Laurentian-Scotian Population)

Malacoraja senta

SARA Status
No Status
NS
Special Concern
SC
Threatened
TH
Endangered
EN
Extirpated
EX

SARA Status

  • No Status NS
  • Special Concern SC
  • Threatened TH
  • Endangered EN
  • Extirpated EX
COSEWIC Status
Not at Risk
NR
Special Concern
SC
Threatened
TH
Endangered
EN
Extirpated
EX

COSEWIC Status

  • Not at Risk NR
  • Special Concern SC
  • Threatened TH
  • Endangered EN
  • Extirpated EX

Description

Smooth Skate (Malacoraja senta) belongs to the Class Chondrichthyes, which includes all shark and skate species. This species is one of the smallest skates in the Northwest Atlantic Ocean, growing up to 66 cm in length and weighing up to 1.2 kg. This species is distinguished from other skates in Canadian waters primarily by the combination of its long tail (equal in length to its body length) and 2 “triangles” of thin, opaque cartilage on its snout. Smooth Skate less than 1 year old (Young-of-the-Year or YOY skates) can be distinguished from other young Northwest Atlantic skates by 1–4 irregular pale “crossbars” or “half-bars” on its tail.

Habitat

Smooth Skate is native to the continental shelf off North America — the only location in the world where this species lives. It is found from southern Georges Bank (south of Cape Cod) north to the Labrador Shelf (Hopedale Channel). Smooth Skate are not continuously distributed throughout their range and are considered to form four populations that are geographically isolated based on water temperature, depth, and other factors that are not yet understood. The Laurentian-Scotian population is distributed along the Southwest Grand Banks, Gulf of St. Lawrence, Scotian Shelf, Bay of Fundy, and Georges Bank.

Smooth Skate usually live at depths between 70 and 480 m and in water temperatures of 2.7–10 °C. Densest concentrations of Smooth Skate occur in troughs surrounding shallower banks, where seawater is warmer. They are found mostly on soft mud (silt and clay), but also on sand, broken shells, gravel, and pebbles. This species is very selective in its diet, eating primarily small bottom-dwelling invertebrates (shrimp, euphausiids, mysids, amphipods, or “sea lice”) throughout most of its life; though, larger Smooth Skate also eat small groundfish.

Threats

Smooth Skate distribution

Approximate boundary of smooth Skate (Laurentian-Scotian Population) distribution in Canada, as adapted from COSEWIC 2012.

Map depicting approximate boundaries of the Laurentian-Scotian population of Smooth Skate. These boundaries encompass the Southwest Grand Banks, Gulf of St. Lawrence, Scotian Shelf, Bay of Fundy, and Georges Bank. This map was adapted from the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) 2012 assessment and status report on the Smooth Skate (Malacoraja senta) in Canada.

COSEWIC identified the following main threats to the Laurentian-Scotian population of Smooth Skate in Canada:

  • Predation – Natural mortality (e.g., predation) of adults may be limiting recovery of this species, particularly in the Southern Gulf of St. Lawrence.
  • Fishery bycatch – There are no directed fisheries for any Smooth Skate population, but Smooth Skate are taken as bycatch in fisheries targeting other groundfish species. It is unknown whether bycatch mortality threatens their recovery and distribution; however, fishing mortality may be low.

Further Information

The Laurentian-Scotian population historically accounted for 90% of Smooth Skate's estimated abundance in Canada and 70% of its Canadian range. Trends in abundance and area of occupancy vary among regions for this large population, but overall numbers have likely been increasing in recent years. Although the Scotian Shelf used to be the center of abundance for this species, its abundance and area of occupancy have declined steeply there since the 1970s and numbers remain low. It is not clear why both trends differ among regions.

For more information, visit the Species at Risk (SARA) Public Registry Profile.

Smooth Skate (Laurentian-Scotian Population)

Smooth Skate

Illustration of a Smooth Skate viewed from its side. It is a flattened fish with a disc-shaped body. This species is distinguished from other skates in Canadian waters primarily by the combination of its long tail (equal in length to its body length) and 2 “triangles” of thin, opaque cartilage on its snout. Smooth Skate less than 1 year old can be distinguished from other young Northwest Atlantic skates by 1–4 irregular pale “crossbars” or “half-bars” on its tail. There is a group of 3–15 small orbital thorns in front of and around each eye, 2–4 shoulder thorns (except 1 per shoulder on skates <1 year old), and a single midline row of 22–32 small thorns that decrease in size from the neck area to the base of its tail (where midline thorns become “invisible” in size among numerous tail spines).

Scientific name: Malacoraja senta
SARA Status: No Status
COSEWIC Status :Special Concern (May 2012)
Region: Newfoundland and Labrador, Quebec, New Brunswick, Prince Edward Island, and Nova Scotia

Did You Know?

Smooth Skate (Laurentian-Scotian Population) reproduce by laying an embryo in a hard-shelled egg case (“Mermaid's purse”) on the bottom of the ocean, and each female produces between 6 and 40 egg cases per year. Hatching success rate is estimated at 38%, meaning approximately 15 hatchlings survive per female each year. Little is known about predators of Thorny Skate, but the embryo developing inside of an egg case has sometimes been found eaten by a shell-drilling gastropod, while juveniles and adults may be eaten by marine mammals, other skates, and larger fish. Thorny Skate have a highly varied diet of bottom-dwelling fish and invertebrates, which changes with prey availability and skate body size; small skates eat more squid, marine worms, and amphipods (“sea lice”), while larger skates eat Sand Lance, Capelin, smaller Haddock, and Snow Crab. 

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