Platyrhinoidis triseriata 

Scope: Global

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Chondrichthyes Rajiformes Platyrhinidae

Scientific Name: Platyrhinoidis triseriata
Species Authority: (Jordan & Gilbert, 1880)
Common Name(s):
English Thornback Ray, Shovelnose, Round Skate, Guitarfish, Thornback, California Thornback

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2006
Date Assessed: 2006-01-31
Assessor(s): Carlisle, A.B. & Garayzar, C.V.
Reviewer(s): Kyne, P.M., Heupel, M.R., Simpfendorfer, C.A. & Cavanagh, R.D. (Shark Red List Authority)
The thornback ray is an inshore species usually found in shallow water in bays, sloughs, lagoons, coastal beaches, and kelp forests. Appears to be common in certain bays, sloughs and lagoons, but not throughout its range. Very little is known about its biology and ecology. Individuals reach 91 cm total length (TL) and litter size ranges from one to 15 pups. This species has no commercial value but is known to be occasionally caught in commercial and recreational fisheries in the US, although catch information from Mexico is lacking. The species is common in parts of its range in California with no identifiable threats in that state. As California represents a significant proportion of the species' distribution it is assessed globally as Least Concern. However, little information is available from Mexican waters where it is found along Baja California, with isolated populations in the Gulf of California. Trawl and inshore net fisheries operate in these areas. This could be cause for concern and although this species cannot be assessed beyond Data Deficient in Mexico at the present time, its status there needs assessing and monitoring if its long-term viability is to be assured.

Geographic Range [top]

Range Description:Endemic to southern USA and northern Mexico in the Eastern Central Pacific: Tomales Bay, California, U.S.A. to Bahía Magdalena/Bahía Las Almejas, Baja California, with isolated populations in the Gulf of California, Mexico (Miller and Lea 1972, Plant 1989, Cruz-Aguero et al. 1994, McEachran 1995, Castro-Aguirre and Perez 1996).
Countries occurrence:
Mexico (Baja California); United States (California)
FAO Marine Fishing Areas:
Pacific – eastern central
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Uncommon north of Monterey Bay, California, U.S.A. (Ebert 2003). The species is very common in some bays and sloughs in California including Elkhorn Slough (D. Ebert, pers comm. 15/9/04). Reported to occur in isolated populations in the Gulf of California (Castro-Aguirre and Perez 1996) and is not as common there as in other parts of its range (J. Bizzarro pers. comm.). Miller and Lea (1972) report the species as common off Baja California, but this would relate to cooler northern waters. Its southern extent of occurrence off Baja California is Bahía Magdalena/Bahía Las Almejas (Cruz-Aguero et al. 1994).
Current Population Trend:Unknown
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:An inshore species usually found in water less than 6 m deep, but which have been recorded to 137 m depth. Primarily found on the mud and sand bottoms of bays and sloughs, lagoons, coastal beaches, and in and around kelp forests. They are known to concentrate in large numbers in certain coastal bays and sloughs (Limbaugh 1955, Feder et al. 1974, Larson and DeMartini 1984, Ebert 2003).

Aplacental yolksac viviparous. Litter sizes range from one to 15 pups that are produced in an annual reproductive cycle. Mating occurs in summer with birthing the following summer (usually in August). Maximum size is 91 cm TL.

Diet consists of polychaetes, crabs, shrimp, squid, and small teleosts such as anchovies, gobies, sardines, sculpins, and surfperch (Roedel and Ripley 1950, Van Blaricom 1982, Love 1996, Ebert 2003). Life history parameters taken from Ebert (2003).

Life history parameters
Age at maturity (years): Unknown.
Size at maturity (total length): 48 cm TL (female); 37 cm TL.
Longevity (years): Unknown.
Maximum size (total length): 91 cm TL.
Size at birth: 11 cm TL.
Average reproductive age (years): Unknown.
Gestation time (months): Unknown.
Reproductive periodicity: Unknown.
Average annual fecundity or litter size: 1 to 15.
Annual rate of population increase: Unknown.
Natural mortality: Unknown.

Threats [top]

Major Threat(s): Thornbacks are not targeted but are known to be occasionally caught in commercial and recreational fisheries in US waters. Little information available on catches in Mexico, but likely to be taken by inshore fisheries in lagoons on the Baja Pacific coast and probably by shrimp trawls in the Gulf of California. Further information is urgently required given the species restricted range in Mexico.

Conservation Actions [top]

Conservation Actions: None currently in place. This ray is common in some areas but very little is known about it, so basic research still needs to be conducted in order to learn more about its biology, ecology, and population dynamics. The population in Mexico needs to be monitored for its importance in fisheries.

The development and implementation of management plans (national and/or regional e.g. under the FAO International Plan of Action for the Conservation and Management of Sharks: IPOA-Sharks) are required to facilitate the conservation and sustainable management of all chondrichthyan species in the USA and Mexico. At the time of writing, the USA has developed a National Plan of Action (NPOA), while Mexico had developed a NPOA but implementation has been blocked by industry (Anon. 2004).

Citation: Carlisle, A.B. & Garayzar, C.V. 2006. Platyrhinoidis triseriata. The IUCN Red List of Threatened Species 2006: e.T60112A12304133. . Downloaded on 24 August 2016.
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