|Scientific Name:||Pseudobatos productus (Ayres, 1854)|
Rhinobatos productus Ayres, 1854
|Taxonomic Source(s):||Last, P.R., Séret, B. and Naylor, G.J.P. 2016a. A new species of guitarfish, Rhinobatos borneensis sp. nov. with a redefinition of the family-level classification in the order Rhinopristiformes (Chondrichthyes: Batoidea). Zootaxa 4117(4): 451-475.|
|Taxonomic Notes:||Last et al. (2016) revised the genus Rhinobatos, transferring glaucostigma, horkelii, lentiginosus, leucorhynchus, percellens, planiceps, prahli, and productus to the new genus Pseudobatos.|
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Assessor(s):||Farrugia, T.J., Márquez-Farías, F., Freedman, R.M., Lowe, C.G, Smith, W.D. & Bizzarro, J.J.|
|Reviewer(s):||Vásquez, V.E. & Lawson, J.|
|Facilitator/Compiler(s):||Kyne, P.M., Ebert, D.A., Walls, R.H.L. & Dulvy, N.K.|
This is an amended version of the 2014 assessment to accommodate recent taxonomic revision of the genus Rhinobatus.
The Shovelnose Guitarfish (Pseudobatos productus) is a medium-sized guitarfish that inhabits shallow coastal waters in the Eastern Central Pacific from central California (USA) to the southern Gulf of California (Mexico). This species is typically found at depths <12 m, but has been recorded to 91.5 m. This guitarfish has a generation length of 9 years and exhibits an annual reproductive cycle with litters of 1-16 pups.
In Mexican waters, this species is taken in directed artisanal elasmobranch fisheries in both the Gulf of California and on the Pacific coast of Baja California, and is also retained as bycatch by demersal trawls and gillnets. This guitarfish is the most heavily targeted batoid in north Pacific Mexico. Catches of the Bahía Almejas fishery in Baja California Sur declined severely following a large increase in effort during the mid- to late 1990s. In Californian waters, recreational fishing derby data from Elkhorn Slough, central California suggest that this species has declined by 74% over three generations. Landings in California have also declined, although these declines do not necessarily correspond to population declines. In 2012, an annual seasonal closure on elasmobranch fishing was implemented from May 1 to July 31 along the Mexican Pacific coast, and other recent monitoring and management changes have been made in Mexico. Nonetheless, given ongoing target and bycatch fisheries for this species in Mexico, an absence of species-specific data in Mexican logbooks, and recreational fishing derbies in the United States, the Shovelnose Guitarfish is is assessed as Near Threatened, as we suspect that this species has declined by nearly 30% over the past three generations.
|Previously published Red List assessments:|
|Range Description:||This species is reported in coastal waters from San Francisco Bay, California to the southern Gulf of California, Mexico (Miller and Lea 1972, Eschmeyer et al. 1983).|
Native:Mexico (Baja California, Baja California Sur, Sinaloa, Sonora); United States (California)
|FAO Marine Fishing Areas:|
Pacific – eastern central
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||There is little information on the population status or trend for this species. Along the coast of northwest Mexico, including the Pacific coast of Baja California and around the Gulf of California, the Shovelnose Guitarfish is the most commonly landed elasmobranch species in the artisanal fisheries (Márquez-Farias 2002, Smith et al. 2009, Cartamil et al. 2011, Ramirez-Amaro et al. 2013). In Bahía Almejas, Baja California elasmobranch fisheries reportedly targeted aggregations of this species. Despite this, researchers did not observe any negative effects on this species at the time of these surveys (1991-1995; Salazar-Hermoso and Villavicencio-Garayzar 1999). The Shovelnose Guitarfish was also the elasmobranch species most captured in the upper Gulf of California (Marquez-Farias 2002, Bizzarro et al. 2009, Smith et al. 2009). It should be noted, however, that catch data reported as the Shovelnose Guitarfish may also include catches of Banded Guitarfish (Zapteryx exasperata). High fishing pressure recorded in this species could cause population declines, so this species should be monitored closely (Ramirez-Amaro et al. 2013).|
Mexican logbooks from fisheries targeting elasmobranchs group guitarfish under a general category, and these data show that reported guitarfish catches have ranged from >1,000 metric tonnes (mt) live weight in 2007, 2009, 2010, and 2014; to between 846 and 937 mt in 2006, 2008, 2011, 2012, and 2013 (CONAPESCA 2006-2014). Changes in Mexican fishing effort are difficult to detect, but effort is estimated to be relatively stable. Because all guitarfishes are grouped under a general category, population declines for this species may go undetected.
Landings of the Shovelnose Guitarfish are monitored in Californian waters, and have declined from 9.26-10.31 tonnes (t) in 2000-2002 to 0.13–1.05 t in 2012–2014 (California Department of Fish and Wildlife 2000-2014). This is likely due to the reduction and redistribution of fishing pressure in the range of this species, and thus may not be correlated with a decline in abundance in Californian waters. In Elkhorn Slough, California, historical data from fishing derbies indicate that catches of the Shovelnose Guitarfish declined by 78% over three generations from the 1950s to the 1970s, and by the mid-1990s catches had undergone a 92% decline from 1950s levels (Carlisle et al. 2007). However, these declines were recorded at the northern extent of this species range, and may be the result of changing environmental conditions, rather than a population decline driven by fishing. In southern California, the Shovelnose Guitarfish was found to be abundant in a small, restored coastal habitat (Farrugia et al. 2011) as well as in San Diego Bay (Allen et al. 2002).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||The Shovelnose Guitarfish commonly inhabits sandy or muddy shallow waters of bays, sloughs, and estuaries, typically in coastal waters shallower than 12 m, but also to depths of 91.5 m (Feder et al. 1974, Love 1996). This species also occurs commonly in intertidal waters (<1 m depth) to feed (J. Bizzarro, pers. comm. 2016). In Baja California, gravid females come during the spring and summer to give birth in shallow bays and estuaries (Villavicencio-Garayzar 1993, Márquez-Farías 2007). Based on fisheries landings, males arrive in late summer to mate and then all individuals depart in the fall (Bizzarro et al. 2009).|
Considerable information on reproductive biology and age-growth has been gathered for this species from both the west coast of Baja California Sur (BCS) in Mexico (Villavicencio-Garayzar 1993, González-García 1998, Downton-Hoffmann 2001, Márquez-Farías 2007) and from Californian waters in the USA (Miller and Lea 1972, Eschmeyer et al. 1983, Timmons and Bray 1997). Life history parameters of Shovelnose Guitarfish can be quite different based on the location that the samples were taken, and the method of measuring the parameters.
This species is aplacental viviparous (bears live young nourished from a yolk sac) and has a continuous reproductive cycle. Gestation takes 4 to 5 months (Márquez-Farías 2007). Pregnant females may contain uterine capsules and large ripe ova in both ovaries at the same time, but the reproductive cycle is annual with a single litter per year (Villavicencio-Garayzar 1993, Márquez-Farías 2007). Fecundity has been reported as 1 to 10 pups/litter (average five; Márquez-Farías 2007) and 6 to 16 pups/litter (Villavicencio-Garayzar 1993), with a 1:1 sex ratio at birth (Márquez-Farías 2007). Size at birth ranges from 20 to 24 cm TL (in San Quintin Bay, Baja California, Mexico; Villavicencio-Garayzar 1993), 15 cm TL (in Almejas Bay, Baja California Sur, Mexico; Eschmeyer et al. 1983), and 17.5 cm TL (in Sonora, Mexico; Márquez-Farías 2007). Multiple estimates also exist for size at maturity ranging from 57–99 cm TL for females (Timmons and Bray 1997, Villavicencio-Garayzar 1993, Downton-Hoffman 1996, Márquez-Farías 2007) and <63–110 cm TL for males (Timmons and Bray 1997, Villavicencio-Garayzar 1993, Downton-Hoffman 1996, Dubois 1981, Talent 1985, Márquez-Farías 2007). Age at maturity is estimated at 7 years for females and 7 to 8.4 years for males (Timmons and Bray 1997). Maximum size is estimated at 156 cm TL for females (Baxter 1966) and 114 cm TL for males (Downton-Hoffman 1996). Longevity is estimated at 11 years (Timmons and Bray 1997). Generation length is estimated to be 9 years (Timmons and Bray 1997).
|Generation Length (years):||9|
|Use and Trade:||This species is utilized for its meat and fins.|
The primary threat to the Shovelnose Guitarfish is most likely the directed artisanal fisheries in Mexico (Bizzarro et al. 2007). Pregnant females are frequently caught in the artisanal gillnet fishery on the west coast of Baja California (Salazar-Hermoso and Villavicencio 1999, Bizzarro 2005) and the coast of Sonora, Gulf of California, Mexico (Márquez-Farias 2002). Gillnet selectivity analysis revealed that mature individuals were most susceptible to capture in the fishery (Márquez-Farías 2005, Márquez-Farías 2011). Neonates and small juveniles are much less abundant in the directed fishery (Bizzarro et al. 2009, Cartamil et al. 2011).
The Shovelnose Guitarfish is also taken as bycatch in demersal trawls (especially shrimp trawlers), and gillnets in Mexican waters. The high catches of mature individuals either by the directed artisanal fishery or in indirect landings most likely are having an effect on the population structure as well as the overall abundance of guitarfish (Bizzarro et al. 2007, Márquez-Farías 2011). In the Bahía Almejas summer batoid fishery, this species is the most abundant in June landings (ca. 51% of catch, catch-per-unit-effort (CPUE) = 21.8 individuals/vessel/day) landings and third most abundant in August landings (ca. 13%, CPUE=2.8 individuals/vessel/day). Catches of the fishery in Bahía Almejas, Baja California has steeply declined after greatly increased effort in the mid to late 1990s and its abundance has almost surely declined in this region as a result of fishing pressure. In Sonora, Mexico, the Shovelnose Guitarfish is the most abundant batoid landed in the artisanal elasmobranch fishery (Márquez-Farías 2002, Bizzarro et al. 2009). In addition, the fishing derbies of Elkhorn Slough seem to have similarly drastically reduced the abundance of Shovelnose Guitarfish (Carlisle et al. 2007).
In the United States, this species is taken by recreational anglers to a limited extent and occasionally sold in local Asian markets in southern California.
The second largest threat to the Shovelnose Guitarfish is habitat modification. Many embayments and estuaries in the northwest Pacific region of Mexico are being modified for shrimp farming. Since this species uses these areas for feeding and reproduction, this could have a detrimental impact on its abundance in affected areas. In United States waters, many of the bays and estuaries have been modified, degraded or destroyed, restricting the coastal areas that can be used by the Shovelnose Guitarfish. It is unclear, however, whether this would significantly impact the survival, fecundity or population resilience of the species.
There are currently no species-specific conservation measures in place in United States or Mexican waters.
In Mexico, a moratorium on the allocation of additional elasmobranch fishing permits was enacted in 1993, but no formal management plan has been implemented for the Shovelnose Guitarfish specifically. Mexico implemented a National Plan of Action (NPOA) in 2004, and began reporting some species-specific data to the Food and Agriculture Organization of the United Nations (FAO). However, only 10% of catches were reported to species level in 2010, with most being grouped by order and above. The United States implemented a NPOA in 2001, with 25% of catches being reported to species level (Fischer et al. 2012). In 2007 Mexican officials approved Regulation NOM-029 which required fisheries targeting sharks to establish a logbook system, regulate fishing gear for small and medium sized fleets, and define areas where fishing is restricted. This species is recorded in these target fisheries, along with other guitarfish species, under the general category of "pez guitarra". In 2012 Mexico also developed a fishing ban on the Pacific Coast that takes place from May 31 to July 31. These efforts should help improve species-specific data, and provide an essential basis for detecting fishery trends and are needed throughout the species’ range.
In Californian waters, a network of 29 marine protected areas (MPAs) were 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 2000–2014). 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). Finally, restoration of coastal habitats along the California coast provides areas for Shovelnose Guitarfish to feed, breed and escape predators, and there is evidence that these restored habitats are being used by this species (Farrugia et al. 2011).
|Citation:||Farrugia, T.J., Márquez-Farías, F., Freedman, R.M., Lowe, C.G, Smith, W.D. & Bizzarro, J.J. 2016. Pseudobatos productus. The IUCN Red List of Threatened Species 2016: e.T60171A104004394.Downloaded on 18 November 2017.|
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