Dipturus laevisBarn-door skate

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Geographic Range

The barndoor skate is found in the northwestern Atlantic Ocean. It is found from the Grand Banks of Newfoundland and the southern side of the Gulf of St. Lawrence, south to North Carolina. It is also undoubtedly reported in Florida where egg cases with embryos washed ashore in the 19th century (Bigelow and Schroeder 1953).

Habitat

Barndoor skates seem to be found in a variety of habitats, from shoreline to nearly 235 fathoms. Most occur primarily around 5 fathoms or 70-80 fathoms. They seem to prefer sandy or gravel bottoms in shallower areas and in deeper waters, muddy bottoms. The skate appears to move closer to shore in the autumn and move further out to sea in the warmer summer months. It is believed that it does not have any north-south migratory patterns. (Bigelow and Schroeder 1953).

Physical Description

The largest barndoor skates found have been 5-6 feet and 30-38 pounds thus deeming it the largest skate in the northwestern Atlantic. The lower surface is white, with blotchy gray spots. The dorsal surface is brown with scattered darker spots. The space between the 2 eyes is approximately 5.5 mm. Like other skates, the barndoor skate has gills. However, the tail lacks large thorns, which distinguishes it from all other skates of the genus Raja in the western north Atlantic except for 2 species. The tail does have 3 rows of smaller thorns.

The dorsal fins are far removed from the tail. There is a larger, misshaped spot on the inner part of each pectoral fin. There are also mucous pores on the ventral surface, marked by black dots and dashes. The barndoor skate has 30-40 teeth.

There are two sexes of barndoor skate. Mature males are smoother than females. Large females are rough, having small spines along a narrow margin from tip of the snout to the level of the nostrils. The young look almost exactly like the adults (Bigelow and Schroeder 1953).

Reproduction

Many aspects of the reproductive cycle of the barndoor skate are still unknown but there are still aspects known. The eggs, which are quite large in size, are deposited from close to the shoreline down to the greatest depths at which the skate is found. The eggs are laid in the winter and hatch either in the late spring or in early summer. The numbers of hatchlings are quite small which gives the barndoor skate a low fecundity. The hatchlings closely resemble adults and range from 180-190 mm (Bigelow and Schroeder 1953).

Behavior

No information concerning behavior or social system could be found for the barndoor skate.

Food Habits

Barndoor skates do not seem to be fussy eaters. They will feed upon large crustaceans, such as lobsters, spider crabs, shrimp and crabs and even isopods. They also add to their diet bivalves like clams, and large gastropods such as worms and squid. Barndoor skates also seem to be more destructive upon fish than other local skates and have been known to bite on almost any type of bait (Bigelow and Schroeder 1953).

Economic Importance for Humans: Positive

The barndoor skate is of no positive economic importance to humans.

Economic Importance for Humans: Negative

If it were added to the Endangered Species list, then trawling in the northwestern Atlantic, which is quite common, would be more tightly restricted. This would place a further strain on the fishermen who must fish longer and harder in order to achieve past yields. Many of the animals that are used in commercial fisheries are preyed on by skates, however, there seem to be so few barndoor skates left that it does not seem to matter. (Bigelow and Schroeder 1953)

Conservation Status

The conservation of the barndoor skate is becoming an increasingly popular subject of heated discussion. Casey and Myers (1998) concluded that it is "close to extinction" due to by-catch. A once common fish in all parts of the Gulf of Maine during the 1950s, it is now rarely found by anglers. Casey and Myers said that the only way to ensure the survival of the barndoor skate is to ban all extensive areas of trawling in the northwestern Atlantic.

Estimates from St. Pierre Bank indicate that the barndoor skate population was near 600,000 during the 1950s and has since plummeted to less than 500 in the 1970s. The barndoor skate population is especially vulnerable due to its low fecundity or number of young that it produces in each hatching.

Following Casey and Myers study, there was a petition in 1999 to the National Marine Fisheries Service (NMFS) to have the barndoor skate added to the Endangered Species list. The NMFS is trying to determine if it needs to be added to the list.

Surprisingly, there is strong opposition to the idea that the barndoor skate is on the brink of extinction. Kenchington (1999) examined Casey and Myers' findings and came to his own conclusion that "the barndoor skate is not near to biological extinction and is showing no sign that it is headed in that direction. Rather, it seems to be experiencing a slow increase in abundance in a setting where human activity poses no threat to its continued existence as a species". In rebuttal to Kenchington's comments, the barndoor skate is missing in 7 of 9 previous locations where barndoor skates were common. (Bigelow and Schroeder 1953; Close 1999; Kenchington 1999; Large 1998)

Other Comments

There is little known and published concerning the barndoor skate. Most of the information concerns physical characteristics and conservation efforts. The world, however, is witnessing the apparent modern extinction of a marine animal that is well documented in the twentieth and twenty-first centuries. For centuries, a creature over one meter in size went unnoticed. Unfortunately, it may continue to do so until it is extinct and exits the pages of books as quickly as it had entered. (Large 1998)

Contributors

Jennifer Basta (author), SUNY College of Environmental Science and Forestry, Kimberly Schulz (editor), SUNY College of Environmental Science and Forestry.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

References

Bigelow, H., W. Schroeder. 1953. Sawfishes, guitarfishes, skates, rays. Sears Foundation for Marine Research 1(2).

Casey, J., R. Myers. 1998. Near extinction of a widely distributed fish. Science, 281: 690-692.

Endangered Species Coalition, 1999. "Close the Barndoor before the Skates Are Gone!" (On-line). Accessed April 26, 2001 (no longer available) at http://www.stopextinction.org/.

Kenchington Ph. D., T. 1999. "Conservation Status of the Barndoor Skate (Raja" (On-line). Accessed April 26, 2001 at http://www.fishingnj.org/skate.htm.

naturalSCIENCE, 1998. "Large Atlantic ray fished to the brink of extinction" (On-line). Accessed April 26, 2001 at http://www.naturalscience.com/ns/cover/cover7.html.