Overview

Comprehensive Description

Biology

Occur from near shore to 183 m depth at temperatures ranging from 14 to 28° C but it is most common inshore of 91 m at 16-25°C. Young occur in shallow bays. Adults tend to live offshore (Ref. 26938). Feed mainly on decapod crustaceans and to a lesser extent on other benthic invertebrates and fishes. 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 6.3 cm long and 3.8 cm wide (Ref. 41359).
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Distribution

Range Description

Western central Atlantic: from off the southeastern coast of Florida, USA, Gulf of Mexico, and Yucatan Bank, Mexico (McEachran and Fechhelm 1998).
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Western Atlantic.
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Western Central Atlantic: Florida, USA and the Gulf of Mexico.
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Physical Description

Size

Maximum size: 333 mm WD
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Max. size

53.0 cm WD (male/unsexed; (Ref. 7251))
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Diagnostic Description

Disk diamond-shaped; round dark spot surrounded by pale ring on base of each pectoral fin. (Ref. 26938). No small pale or dark spots on upper surface of disk, but sometimes dark blotches. No scapular spines, 1 middorsal row of spines. Distance from ocellus to eye usually less than or about equal to distance between ocelli. Snout with a clear area on each side (Ref. 7251). Upper surface rich chocolate or coffee brown, translucent on either side fo rostral cartilage. Lower surface plain white (Ref. 6902).
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Type Information

Type for Raja texana
Catalog Number: USNM 84162
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Fishes
Collector(s): Chandler. Asa C.
Year Collected: 1920
Locality: Houston, Texas, Harris County, Texas, United States, Gulf of Mexico, North America, Atlantic
  • Type:
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
This species occurs in marine waters nearshore and offshore up to 183 m and temperatures between 14–28°C (Smith, 1997); however, it most commonly occurs at 15–110 m at temperatures of 16–25°C (McEachran and Fechhelm, 1998). Young occur in shallow bays whereas adults tend to live offshore (Smith 1997); however, all sizes have been collected in bottom and pelagic trawls in NOAA fishery independent surveys in the US Gulf of Mexico (unpublished data NOAA Mississippi Labs, A. DeBose and A. Hamilton).

This species is oviparous with a distinct sexual dimorphism between males and females. The ovaries of the female are functional on both sides. Once the eggs are mature, they are released from the ovaries, fertilized in the upper part of the shell gland, are enclosed with yolk and albumen in a capsule formed by the lower shell gland. These capsules vary widely in size and are believed to be associated with parental body size. The capsules are light brown and have the characteristic horns on the four corners. Typically, there is only one fertilized egg found in a single capsule. These capsules are flat on one side and convex on the other. The female will often deposit eggs in sandy or muddy flats. When the young hatch from the capsules, they are fully formed and are similar in appearance to adults (unpublished data, J. Sulikowski).

Analysis of stomach contents from 222 immature (195 non-empty; mean DW = 23.5 cm) and 191 mature animals (167 non-empty; mean DW = 32.2 cm) in the northern Gulf of Mexico indicate shrimp (mostly euphasiids) make up 91% IRI of immature skate diet. Fish make up the remainder of immature skate diet. Mature skate diet was also predominantly shrimp (65 %IRI); however, fishes made up a much larger percentage (25 %IRI). Crabs were also relatively important in the diet of mature animals (4 %IRI). This suggests that roundel skate exhibit ontogenetic changes in diet with size and maturity (Bethea et al. In prep).

Systems
  • Marine
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Depth: 0 - 90m.
Recorded at 90 meters.

Habitat: demersal.
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Environment

demersal; marine; depth range ? - 183 m
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Depth range based on 115 specimens in 1 taxon.
Water temperature and chemistry ranges based on 69 samples.

Environmental ranges
  Depth range (m): 15 - 212
  Temperature range (°C): 14.721 - 26.008
  Nitrate (umol/L): 0.202 - 15.775
  Salinity (PPS): 35.554 - 36.529
  Oxygen (ml/l): 3.107 - 4.993
  Phosphate (umol/l): 0.093 - 0.731
  Silicate (umol/l): 1.145 - 6.469

Graphical representation

Depth range (m): 15 - 212

Temperature range (°C): 14.721 - 26.008

Nitrate (umol/L): 0.202 - 15.775

Salinity (PPS): 35.554 - 36.529

Oxygen (ml/l): 3.107 - 4.993

Phosphate (umol/l): 0.093 - 0.731

Silicate (umol/l): 1.145 - 6.469
 
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Trophic Strategy

Occurs from near shore to 183 m depth at temperatures ranging from 14 to 28° C but it is most common inshore of 91 m at 16 to 25° C. Young occur in shallow bays. Feeds mainly on decapod crustaceans and to a lesser extent on other benthic invertebrates and fishes.
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Life History and Behavior

Life Cycle

Oviparous, paired eggs are laid. Embryos feed solely on yolk (Ref. 50449). Distinct pairing with embrace. oung may tend to follow large objects, such as their mother (Ref. 205).
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Life Expectancy

Lifespan, longevity, and ageing

Maximum longevity: 9 years (wild)
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Raja texana

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
DD
Data Deficient

Red List Criteria

Version
3.1

Year Assessed
2009

Assessor/s
Bethea, D.M., Carlson, J. & Sulikowski, J.

Reviewer/s
Valenti, S.V. & Musick, J.A. (Shark Red List Authority)

Contributor/s

Justification
The Roundel Skate (Raja texana) occurs in marine waters nearshore and offshore up to 183 m. It is distributed off the southeastern coast of Florida, USA, Gulf of Mexico, and Yucatan Bank, Mexico and is a potential bycatch in demersal trawls throughout this range. While a trend in abundance for a 30 year trawl data set in the Gulf of Mexico indicate that this species may be slightly increasing in abundance, which might warrant a status of Least Concern, this abundance trend is only from one series. Moreover, the overall productivity of this species is still unknown. Therefore this species is assessed as Data Deficient until further information is available to conduct a full evaluation of the impact of fisheries on the population.
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Population

Population
Unknown.

Population Trend
Unknown
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Threats

Major Threats
The species is potentially caught as bycatch in demersal trawls that occur off the southeastern coast of Florida, USA, and in the Gulf of Mexico and probably discarded. It is also taken as bycatch in the butterfish fishery.
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Data deficient (DD)
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Management

Conservation Actions

Conservation Actions
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Relevance to Humans and Ecosystems

Benefits

Importance

fisheries: minor commercial; bait: occasionally; price category: medium; price reliability: questionable: based on ex-vessel price for species in this genus
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Wikipedia

Raja texana

Raja texana, the roundel skate or Texas clearnose skate, is a species of cartilaginous fish in the family Rajidae. It is found in the Gulf of Mexico, Southeast Florida and the Yucatan Peninsula.

Description[edit]

The disc of the roundel skate is diamond-shaped. The short rounded snout has a clear area of skin on either side. The rest of the dorsal surface is an unblotched chocolate brown colour, although sometimes there are darker patches. A pair of distinctive dark eyespots with pale pink rims lie on either side of the middle of the dorsal surface (these may confuse potential predators). A row of thorns runs along the midline of the back, but there are no venomous spines. The medium-length tail has a short dorsal fin near its tip and a small caudal fin. Males become mature at about 5 years old at a length of about 44 centimetres (17 in), while females are mature a year later at a length of about 53 centimetres (21 in).[3]

Distribution and habitat[edit]

The roundel skate is native to the southeastern coast of Florida, the Gulf of Mexico and the Campeche Bank, a shallow area of sea off the northern coast of the Yucatan Peninsula.[1] It usually occurs on sand, crushed shell or shingle to depths of about 180 metres (590 ft).[3]

Biology[edit]

Adult roundel skates feed predominantly on shrimp (65%), but also take fish (25%) and sometimes crabs and other crustaceans. The diet of juveniles is over 90% shrimp, with the rest composed of small fish.[1]

The roundel skate is sexually dimorphic, with the males usually being smaller than the females. In reproduction, the male's claspers are inserted into the female's cloaca, and fertilisation is internal. As the fertilised egg passes down the uterus, albumen and yolk are added and it is placed in a rectangular collagenous egg case known as a mermaid's purse.[3] This is pale brown, flat on one side and rounded on the other, with tendrils at the corners. The developing embryo feeds on the yolk, and some months later emerges as a fully formed juvenile fish about 11 centimetres (4.3 in) long.[3]

Status[edit]

The IUCN has classified this fish as "Data Deficient" in its Red List of Threatened Species. This is because insufficient evidence is available to compare present day populations with those of the past and so its population trend is unknown.[1]

References[edit]

  1. ^ a b c d Bethea, D. M.; Carlson, J.; Sulikowski, J. (2008). 'Raja texana'. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 2013-07-17.
  2. ^ a b Bailly, Nicolas (2013). "Raja texana Chandler, 1921". World Register of Marine Species. Retrieved 2013-07-17. 
  3. ^ a b c d DeValerio, Kate. "Roundel skate". Biological Profiles. Florida Museum of Natural History. Retrieved 2013-07-17. 
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