Platyrhinoidis triseriata 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Chondrichthyes Rajiformes Platyrhinidae

Scientific Name: Platyrhinoidis triseriata (Jordan & Gilbert, 1880)
Common Name(s):
English Thornback Ray, California Thornback, Thornback
Platyrhina triseriata Jordan & Gilbert, 1880
Taxonomic Source(s): Eschmeyer, W.N., Fricke, R. and Van der Laan, R. (eds). 2016. Catalog of Fishes: genera, species, references. Updated 1 July 2016. Available at: (Accessed: 1 July 2016).

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2016
Date Assessed: 2015-10-07
Assessor(s): Lawson, J., Carlisle, A.B. & Villavicencio-Garayzar, C.J.
Reviewer(s): Lyons, K. & Pien, C.
Facilitator/Compiler(s): Kyne, P.M., Walls, R.H.L., Ebert, D.A. & Dulvy, N.K.
The Thornback Ray (Platyrhinoidis triseriata) is an inshore species usually found in bays, sloughs, lagoons, coastal beaches, and kelp forests <6 m deep, but with a maximum reported depth of 137 m. Individuals reach a maximum size of 91 cm total length and litter size ranges from one to 15 pups. This species is not targeted, but is known to be caught incidentally in commercial and recreational fisheries in the United States, and likely in Mexico. In southern California, commercial bycatch and fishing derby data suggest that this species is common, and abundance has increased since the 1950s, possibly due to oceanographic conditions becoming more favourable. Off the Pacific coast of Baja California, Mexico, this species was encountered in artisanal fishing community surveys from 1998 and 1999, but abundance or trend data are not available. In California, which represents approximately half of this species' range, management measures have been put into place that act to increase habitat protection and decrease fishing pressure. These management measures are likely to benefit this species. Given that this species appears to be abundant or increasing in the northern part of its range, and that threats to this species are being managed or reduced in the northern part of its range, this species is assessed as Least Concern globally. However, the impact of incidental capture on this species in Mexico is not fully understood, and abundance and population trend estimates are needed for the southern part of its range.
Previously published Red List assessments:

Geographic Range [top]

Range Description:The Thornback Ray is endemic to the southwestern United States and northern México in the Eastern Central Pacific. It ranges from Tomales Bay, California, U.S.A. to Bahía Magdalena/Bahía Las Almejas, Baja California, with isolated populations in the Gulf of California, México (Miller and Lea 1972, Plant 1989, de la Cruz-Agüero et al. 1994, McEachran 1995, Castro-Aguirre and Perez 1996). This ray is uncommon north of Monterey Bay, California, U.S.A. (Ebert 2003), and is very common in some bays and sloughs in California including Elkhorn Slough (D. Ebert, pers comm. 15/9/04).
Countries occurrence:
Mexico (Baja California); United States (California)
FAO Marine Fishing Areas:
Pacific – eastern central
Additional data:
Lower depth limit (metres):137
Upper depth limit (metres):6
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:No information is available on population or subpopulation sizes for this species. Commercial bycatch of skates and rays in California reference the Thornback Ray as one of the four most common taxa in these landings, although not all caught skates and rays are identified to species (Leet et al. 2001). A report on the status of skate and ray populations in California noted that while landings underwent an increase from 103 metric tons (mt) in 1989 to 868 mt in 1999, this does not necessarily reflect an increase in abundance (Leet et al. 2001). Species-specific commercial landings data are not available for this species in California.

Carlisle et al. (2007) analysed recreational fishing derby data from 1951 to 1995 in Elkhorn Slough, California. Derbies were held in the summer, in an attempt to control shark and ray populations that were suspected of reducing shellfish and finfish populations in the slough. The Thornback Ray was a relatively rare catch in the early derby years, and increased in the 1960s and 1970s, possibly due to a change in oceanographic conditions (Carlisle et al. 2007). Catches reported during the fishing derby were highly skewed towards females. As of 2006, they were reportedly one of the most abundant elasmobranchs in the Elkhorn Slough (Carlisle, unpub. data 2006), and increased in abundance as the Shovelnose Guitarfish (Rhinobatos productus) decreased. The derbies concluded in 1995, and fishing pressure on this species was greatly reduced in this area.

Along the Pacific coast of Baja California, historically this species was reported as common (Miller and Lea 1972). More recently, along the Pacific coast of Baja California Sur, México, this species was only encountered in artisanal fishing communities north of Bahía Magdalena (N=15 individuals; catch-per-unit effort of 0.04 individuals/vessel/trip), during surveys that took place between 2000 to 2010 (Ramirez-Amaro et al. 2013). It was absent from artisanal fishing community surveys conducted in the Gulf of California between 1998 and 1999 (Bizzarro et al. 2009a,b), although it was reported to occur in isolated populations in the Gulf of California (Castro-Aguirre and Perez 1996).
Current Population Trend:Unknown
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:The Thornback Ray is an inshore species usually found in water <6 m deep, but with a maximum reported depth of 137 m. This ray is primarily found on the mud and sand bottoms of bays and sloughs, lagoons, coastal beaches (Carlisle et al. 2007), 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), and appear seasonally (spring/summer) in Elkhorn Slough, California (C. Pien, pers. obs., 3 February 2016).

Reproduction in the Thornback Ray is aplacental yolksac viviparous. Litter sizes range from one to 15 pups that are produced in an annual reproductive cycle, and size at birth is 11 cm total length (TL; Ebert 2003). Mating occurs in summer with birthing the following summer (usually in August). Size at maturity is 48 cm TL in females and 37 cm TL in males, with a maximum size of 91 cm TL (Ebert 2003). There is no estimate of generation length available for this species, but its congener the Fanray (Platyrhina sinensis) was estimated to have a generation length of 7.45–8 years (Kume et al. 2008)
Generation Length (years):7.45-8

Use and Trade [top]

Use and Trade: This species is likely used for its meat, although no details are known at this time.

Threats [top]

Major Threat(s): The Thornback Ray is not targeted, but is known to be occasionally caught in commercial and recreational fisheries in United States (i.e., Monterey Fisherman's Wharf and Elkhorn Slough, California, C. Pien, pers. obs., 3 February 2016) and in Mexican waters. There is little information available on catches in Mexico, but this species is 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: There are currently no species-specific conservation measures in place in United States or Mexican waters.

While no species-specific management plan has been implemented for the Thornback Ray in Mexico, some fisheries are required to record species-specific data under the general category of “manta raya” (a term that encompasses all batoids) in logbooks. While not all fisheries have established a logbook system, in fisheries targeting sharks they have been required since 2006. Additionally, in 2012 Mexico implemented a seasonal fishing closure from May 31 to July 31 for fisheries targeting elasmobranchs on the Pacific Coast.

In Californian waters, a network of 29 marine protected areas (MPAs) was implemented in 2007 under California's Marine Life Protection Act, representing approximately 204 square miles (~18%) of state waters in the central coast region (California Department of Fish and Wildlife 2015). Due to these MPAs, most trawlers are restricted to operating in deeper waters, and only in central and northern California. As a result, fishing effort in the California trawl fishery has been reduced, and catches of this species have also likely been reduced (D. Ebert, pers. obs. 2007).

Citation: Lawson, J., Carlisle, A.B. & Villavicencio-Garayzar, C.J. 2016. Platyrhinoidis triseriata. The IUCN Red List of Threatened Species 2016: e.T60112A80673588. . Downloaded on 22 April 2018.
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