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Raja binoculata

(Big Skate, Big Skate)

Overview

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Largest skate in North America (Ref. 2850). Feed on crustaceans and fishes (Ref. 6885). Oviparous . Distinct pairing with embrace. Young may tend to follow large objects, such as their mother (Ref. 205). Eggs are oblong capsules with stiff pointed horns at the corners deposited in sandy or muddy flats (Ref. 205). Egg capsules are 22.8-30.5 cm long and 11.0-19.4 cm wide (Ref. 41249, 41300, 41357). Pectoral fins utilized for human consumption (Ref. 2850). Marketed fresh and frozen; eaten fried and baked (Ref. 9988).

Common Names

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Click on the language to view common names.

Common Names in Danish:

Stor Rokke

Common Names in Dutch:

Grote Rog

Common Names in English:

Big Skate

Common Names in French:

Raie

Common Names in Mandarin Chinese:

雙斑鰩, 雙斑鰩, 双斑鳐

Common Names in Polish:

Raja Wielka

Common Names in Russian:

скат большой калифорнийский, скат большой калифорнийский, Skat

Common Names in Salish:

K´ak´ew´, K'ak'ew'

Common Names in Spanish:

Raya Brava, Raya Bruja Gigante, Raya Gigante

Common Names in Tsimshian:

Gandah, K´andah, K'andah

Description

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Family Rajidae

Benthic rays occurring in all oceans, from Arctic to Antarctic waters and from shallow coastal shelfs to abyssal regions; rare in tropical shallow waters or near coral reefs; some species enter brackish waters. Disc quadrangular to rhomboidal . Mouth transversed to arched, with numerous teeth. Five pairs of ventral gill slits . Tail very slender, with lateral folds, usually 2 reduced dorsal fins and a reduced caudal fin. Electric organs weak, developed from caudal muscles. Skin prickly in most species, the prickles often in a row along midline of dorsal. Oviparous ; eggs in a horny capsule with four long tips . A reversal to egg-laying from live-bearing was observed in this group based on fossil records (Ref. 50449). Skates feed on other benthic organisms. Skate wings are considered good eating. The following subgenus have been elevated to the genus level: Amblyraja, Dipturus, Fenestraja, Leucoraja, Okamejei, Rajella, Rostroraja (Ref. 27314).The family Rajidae belongs to the Class Elasmobranchii (sharks and rays) and the Order Rajiformes. It contains 14 genera and 200 species. It may be found in Marine and Brackish environments and is primarily Marine. Members of this family are not used in the aquarium trade. Reproductively, most members of this family are nonguarders. The main mode of swimming of adult fish in this family is rajiform. Compared with other fish, the activity level of this family tends to be normal. Members of this family have been dated back to the Cretaceous period. Etymology of this family name : Latin, raja = ray

Physical Description

Species Raja binoculata

Distinctive Features: The big skate has a flattened diamond-shaped body with a stiff snout tapering to a blunt point . The small eyes are positioned on the dorsal surface some distance from the pointed snout with large spiracles just posterior to the eyes.

The mouth is on the ventral surface along with the five gill slits . The pectoral fins are not clearly distinct , attaching the snout with the body. These fins have a concave anterior edge between the snout and pointed tips of the fins. The two small dorsal fins are located on the tail while the anal and caudal fins are absent. The pelvic fins are large and moderately concave and weakly notched along the free margins . The tail is long and narrow and has a fleshy keel on either side.

Dentition: The teeth of the big skate are small. They are arranged in rows with bases touching and raised cusps .

Denticles : There is an irregular row of approximately 33 middorsal thorns that runs down the back and tail to the first dorsal fin. There is a single middorsal thorn located just behind the orbits. Also, orbital thorns are located between the eyes but may remain buried under the skin in some individuals. These thorns may become more prominent as the skate ages.

Small, placoid scales are present, although rather sparsely, on the body, tail and posterior portion of the head .

Color:

The big skate has mottled coloration on the dorsal surface including brown, reddish brown, dark gray and black. There may also be small pale spots and scattered dark blotches. There are two large black spots , resembling eyes, on the dorsal surface of the pectoral fins. Each spot has a pale border and dark center. Biologists believe that these "eyes" may confuse potential predators , with the skate appearing much larger than it is. The ventral surface ranges from white to a muddy white sometimes with dark blotches.

Size/Age/Growth

Aptly named the "big" skate, this species is the largest skate in North American waters. The maximum reported size of the big skate is 7.9 feet (2.4 m ) total length, however this species usually does not reach lengths beyond 6 feet (1.8 m) and weights of 200 pounds (91 kg ). Males reach maturity at approximately 7-8 years of age and lengths of 3.2-3.6 feet (0.9-1.1 m); females mature at about 12-13 years of age and lengths of 4.3-4.6 feet (1.3-1.4 m).

Habitat

In waters from the intertidal range to depths of 394 feet (120 m ), the big skate is found along the coast in estuaries, bays , and over the continental shelf. Although this skate is sometimes observed in low stands of kelp, it is more common on sandy and muddy bottoms . It is usually seen hiding motionless in the bottom sediments with only eyes protruding, camouflaged from potential predators . When it does move, swimming occurs by the undulation of the pectoral fins, which makes the skate appear as though it is "flying" gracefully through the water.

Typically found in water with a depth of 0 to -4,869 meters (0 to -15,974 feet).Mean = -368.720 meters (-1,209.711 feet), Standard Deviation = 790.670 based on 541 observations. Ocean depth information for each observation from British Oceanographic Data Centre.

Biome: Saltwater . Demersal .

Ecology:
List of Habitats :9.1Marine Neritic - Pelagic 10.1Marine Oceanic - Epipelagic (0-200m)

Biology

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Diet

The big skate feeds on marine invertebrates such as shrimp, worms, and clams as well as on fishes including the great sculpin (Myoxocephalus polyacanthocephalus).

Reproduction

The big skate is an oviparous , or egg-laying species. It has probably the largest egg capsules in the Rajidae family , with each measuring 9-12 inches (22.8-30.5 cm) long and 4-7 inches (11.0-19.4 cm) wide. The egg capsules are oblong in shape with horns at each corner. The only known egg capsules to contain more than one egg inside are those of the big skate and mottled skate (R. pulchra). The egg capsules of the big skate commonly contain 3-4 eggs, although up to 7 have been documented. The female releases the egg capsules in pairs on sandy or muddy substrate. The egg capsules release the hatchlings about nine months after being released from the female. The empty black egg cases, referred to as mermaid's purses , sometimes wash ashore and are found by beach walkers.

Behavior

Predators:

Large predatory bony fishes and sharks consume big skates . One such documented predator is the sevengill shark (Notorynchus cepedianus). The egg capsules are sometimes eaten by elephant seals.

Parasites:

Copepods parasitize a variety of marine fishes with the big skate being no exception. The copepod Lepeophtheirus cuneifer sp. nov. is one such documented parasite of the big skate.

Taxonomy

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Unambiguous Synonyms

  1. Dipturus binoculata (Girard, 1855)
  2. Raja cooperi Girard, 1858

Notes

Name Status: Accepted Name . Synonym: Raja cooperi. Latest taxonomic scrutiny: November 15, 1999.

Family : Skates .

The big skate was originally described by Girard in 1855 as Raja binoculata . Although another combination , Dipturus binoculata, was also used to describe the big skate, Raja binoculata remains the scientifically valid name . The genus name Raja is derived from the Latin "raja" meaning skate and the species name binoculata means two eyes, referring to the spots on the pectoral fins. A synonym used to refer to this species in previous scientific literature is Raja cooperi Girard 1858.

Common Names : In the English language, the common name for this species is big skate. Other common names include gandah (Tsimshian), grote rog (Dutch), k'ak'ew (Salish), k'andah (Tsimshian), raie (French), raja wielka (Polish), raya gigante (Spanish) and scat (Russian). Other common names: Tsimshian: Gandah, Dutch: Grote rog, Salish: K'ak'ew', Tsimshian: K'andah, French: Raie, Polish: Raja wielka, Spanish: Raya gigante, Russian: Skat, Danish: Stor rokke

Similar Species

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Species similar in appearance and sharing habitat with the big skate include:

California skate (R. inornata) which has a pointed snout, deeply notched pelvic fins, and slightly convex anterior edges of the pectoral fins.

Sandpaper skate (R. kincaidi) which lacks orbital thorns and has a thorn on the shoulders in center of body on each side of the midline of the skate.

Longnose skate (R. rhina) which has deeply concave anterior margins of the pectoral fins and deeply notched pelvic fins. Starry skate (R. stellulata) which has small ocelli and convex anterior edges of the pectoral fins as well as is covered with thorns. Roughtail skate (R. trachura) which has no large thorns on the body and is dark gray or black both on the dorsal and ventral surfaces.

Members of the genus Raja

There are approximately 96 species in this genus:

R. ackleyi (Ocellate Skate) · R. ackleyi ornata · R. actispina · R. africana (African Ray) · R. agassizii · R. aguja · R. albolinea · R. antiqua · R. arctowskii · R. asterias (Atlantic Starry Skate) · R. atriventralis · R. bahamensis (Bahama Skate) · Leucoraja leucosticta · Rajella bathyphila · R. binoculata (Big Skate) · R. brachyura (Blonde) · R. brasiliensis · R. breviraja · R. cervigoni (Finspot Ray) · R. clauata · R. clavata (Maiden Ray) · R. cortezensis (Cortez' Ray) · R. dipturus · R. dux · R. eglanteria (Clear-Nosed Brier Skate) · R. equatorialis (Ecuatorial Ray) · R. equatoriallis · Psammobatis extenta · R. falsavela intermedia · R. falsavela maggiore · R. farishi · R. fulginea · Rajella bigelowi · R. fyllae lipacantha · R. garmani caribbaea · R. garmani virginica · R. clavata · R. granulata · R. herwigi (Cape Verde Skate) · R. inornata (California Ray) · R. inornuata · R. koreana (Korean Skate) · R. lamprieri · R. lentiginosus · R. lentignosa · Rajella barnardi · Dipturus oxyrinchus · R. macrorhynchus · R. maderensis (Madeira Ray) · R. maroccana · R. microocellata (Owl Ray) · R. miraletus (Brown Ray) · R. montagui (Homelyn Ray) · R. montereyensis · R. naevis · R. ocellifera · R. brachyura · R. ornata · R. oxyrhinchus · R. oxyrynchus · R. pastinaca altavela · R. platna · Neoraja stehmanni · R. polystigma (Speckled Ray) · R. porosa fusca · R. psammobatis · R. pulchra (Mottled Skate) · R. clavata · R. purpuri · R. purpuri-ventralis · R. purpuri-ventris · Leucoraja circularis · R. radiataa · R. radula (Rough Ray) · Bathyraja maccaini · R. rhina (Longnose Skate) · R. rondeleti (Rondelet's Ray) · R. rouxi · R. scabra · R. scabrata · R. sephen uarnak · R. spincauda · R. spinosa · R. spinossismus · R. spp · R. stabuliformis · R. stellulata (Pacific Starry Skate) · R. straeleni (Biscuit Skate) · R. subgen. · R. texana (Roundel Skate) · Malapterurus electricus (Skates) · Dasyatis guttata · R. umbra · R. undulata (Painted Ray) · R. velezi (Rasptail Ray) · R. whitleyi (Great Skate)

Bibliography

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More Info

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Notes

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Contributors

Data Sources

Accessed through GBIF Data Portal March 02, 2008:

Identifiers

Footnotes

Last Revised: 2008-09-06