Skate (fish)

Skates
Temporal range: Late Cretaceous–Recent

[1]

Arctic skate, Amblyraja hyperborea
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Superorder: Batoidea
Order: Rajiformes
Berg, 1940
Family: Rajidae
Bonaparte, 1831

Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. More than 200 species have been described, in 30 genera. The two subfamilies are Rajinae (hardnose skates) and Arhynchobatinae (softnose skates).

Genera

Skates versus Rays

Mermaid's purse, or the protective egg case of a skate
Skates swim with their pectoral fins
Comparison of skates and stingrays
Superficially, skates and stingrays appear somewhat similar.
Skate
Stingray
However, there are fundamental differences.
Characteristic Skates Rays Sources
Reproduction Skates are oviparous, that is they lay eggs. Their fertilized eggs are laid in a protective hard case called a mermaid's purse. Rays are viviparous, that is, they bear their young inside their bodies and give birth to them alive. [2]
Dorsal fin Distinct Missing or vestigial [2]
Pelvic fins Fins are divided into two lobes Fins have one lobe [3]
Tail Fleshy tails which lack spines Whip-like with one or two stinging spines [2][3]
Protection Rely on "thorny projections on their backs and tails for protection from predators" Rely on their stinging spines or barbs for protection [2]
Teeth Small "Plate-like teeth adapted for crushing prey" [2]
Size Usually smaller than rays Usually larger than skates [2]
Colour Often drab, brown or gray (but not always) Often boldly patterned (but not always) [3]
Habitat Often deep water (but not always) Often shallow water (but not always) [3]

Conservation

Skates have slow growth rates and, since they mature late, low reproductive rates. As a result, skates are vulnerable to overfishing and appear to have been overfished and are suffering reduced population levels in many parts of the world. The barndoor skate, Raja laevis, is currently listed with the IUCN as vulnerable due to being severely overfished.[4] However, population data are lacking to determine the exploitation of the big skate at this time.

In 2010, Greenpeace International added the barndoor skate, bottlenose skate, spotback skate, and maltese skate to its seafood red list. "The Greenpeace International seafood red list is a list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries."[5]

See also

References

  1. ↑ Froese, Rainer, and Daniel Pauly, eds. (2009). "Rajidae" in FishBase. January 2009 version.
  2. 1 2 3 4 5 6 Ichthyology: Ray and Skate Basics Florida Museum of Natural History. Retrieved 21 March 2013.
  3. 1 2 3 4 Skate or Ray? ReefQuest Centre for Shark Research. Retrieved 212 March 2013.
  4. ↑ Florida Museum of Natural History
  5. ↑ Greenpeace International Seafood Red list
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