Rhinobatos productus

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	CHONDRICHTHYES	RAJIFORMES	RHINOBATIDAE

Scientific Name:

Rhinobatos productus

Species Authority:

Ayres, 1854

Common Name/s:

English	–	Northern Guitarfish, Pointed-nosed Guitarfish, Shovelnose Guitarfish
Spanish	–	Guitarra

Assessment Information [top]

Red List Category & Criteria:	Near Threatened ver 3.1
Year Assessed:	2006
Assessor/s	Márquez, F., Smith, W.D. & Bizzarro, J.J.
Evaluator/s:	Kyne, P.M., Heupel, M.R. & Simpfendorfer, C.A. (Shark Red List Authority)
Justification: A medium-sized (to 156 cm total length) guitarfish inhabiting shallow waters of bays, sloughs and estuaries in the Eastern Central Pacific from central California (USA) to the southern Gulf of California (Mexico). Typically found in water shallower than 12 m, but has been recorded to 91.5 m. Reaches at least 11 years of age, exhibiting 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. Also landed when taken indirectly by demersal trawls and gillnets. Its occurrence is strongly seasonal, peaking in spring-summer; mostly due to gravid females migrating to shallower waters, where they become vulnerable to bottom gillnets used in local artisanal fisheries. Rhinobatos productus is the most heavily targeted batoid in north Pacific Mexico in a fishery that targets primarily gravid females before they pup. The fishery in Bahía Almejas, Baja California has severely declined after greatly increased effort in the mid to late 1990’s and its abundance has almost surely declined in this region as a result of fishing pressure. Further data is required on trends in catches in Mexico, but given the heavy fishing pressure on this species, particularly on gravid females, across a large portion of its relatively restricted range, it is assessed as Near Threatened. It is, however, Least Concern in the USA where only a limited sporadic fishery exists in southern Californian waters.

Geographic Range [top]

Range Description:	This species is reported from San Francisco Bay, California to the southern Gulf of California, Mexico (Miller and Lea 1972, Eschmeyer 1983). Occurrence of this species north of Point Conception, CA, has become rare in recent years, however, and the current range does not extend beyond Elkhorn Slough, central CA. This is likely a result of changing oceanic conditions and not overfishing.
Countries:	Native: Mexico (Baja California, Baja California Sur, Sinaloa, Sonora); United States (California)
FAO Marine Fishing Areas:	Native: Pacific – eastern central

Population [top]

Population:	In the northwest of Mexico, the shovelnose guitarfish is abundant in spring and summer close to the shore. No other information on the abundance, population size, or degree of fragmentation of this species is known from its range.
Population Trend:	Unknown

Habitat and Ecology [top]

Habitat and Ecology:	The shovelnose commonly inhabits sandy or muddy shallow waters of bays, sloughs, and estuaries, typically in waters shallower than 12 m, but also to depths of 91.5 m (Feder et al. 1974, Love 1996). 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 unpublished data) and from US Californian waters (Miller and Lea 1972, Eschmeyer et al. 1983, Timmons and Bray 1997). This species is aplacental viviparous. Fecundity has been reported as 1 to 10 pups/litter (average five) (Márquez-Farías unpublished data) and 6 to 16 pups/litter (Villavicencio-Garayzar 1993). Gestation takes 4 to 5 months (Márquez-Farías unpublished data). The species has a continuous reproductive cycle. 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 unpublished data). Feeds on a variety of benthic invertebrates (i.e., molluscs, crustaceans, worms) and fishes (Ferguson and Cailliet 1990). In Bahía Almejas, its diet consists primarily of crustaceans, including pea crabs, benthic shrimp and swimming crabs and occasional takes small razor clams and fishes (Bizzarro 2005). Life history parameters Age at maturity: Female: 7 years (Timmons and Bray 1997); Male: 7 to 8.4 years (Timmons and Bray 1997). Size at maturity (total length): Female: 99 cm TL (Timmons and Bray 1997), 66 cm TL (Villavicencio-Garayzar 1993), 87 cm TL (Dowton-Hoffman, 1996); Male: 91 to 100 cm TL (Timmons and Bray 1997), <63 cm TL (Villavicencio-Garayzar 1993), 80 cm TL (Dowton-Hoffman 1996), 92 cm TL (Dubois 1981), 110 cm TL (Talent 1985). Longevity: 11 years (Timmons and Bray 1997). Maximum size (total length): Females: 156 cm TL (Baxter 1966); Males: 114 cm TL (Dowton-Hoffman 1996). Size at birth): 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), 17.5 cm TL in Sonora, Mexico (Márquez-Farías unpublished data). Average reproductive age (years): Unknown. Gestation time: 4 to 5 months in Sonora, Mexico (Márquez-Farías unpublished data). Reproductive periodicity: Annual (Villavicencio-Garayzar 1993, Márquez-Farías unpublished data). Average annual fecundity or litter size: 1 to 10 pups/litter (average 5) (Márquez-Farías unpublished data), 6–16 pups/litter (Villavicencio-Garayzar 1993). Annual rate of population increase: Unknown. Natural mortality: Unknown.
Systems:	Marine

Habitat and Ecology:

The shovelnose commonly inhabits sandy or muddy shallow waters of bays, sloughs, and estuaries, typically in waters shallower than 12 m, but also to depths of 91.5 m (Feder et al. 1974, Love 1996).

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 unpublished data) and from US Californian waters (Miller and Lea 1972, Eschmeyer et al. 1983, Timmons and Bray 1997). This species is aplacental viviparous.

Fecundity has been reported as 1 to 10 pups/litter (average five) (Márquez-Farías unpublished data) and 6 to 16 pups/litter (Villavicencio-Garayzar 1993). Gestation takes 4 to 5 months (Márquez-Farías unpublished data). The species has a continuous reproductive cycle. 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 unpublished data).

Feeds on a variety of benthic invertebrates (i.e., molluscs, crustaceans, worms) and fishes (Ferguson and Cailliet 1990). In Bahía Almejas, its diet consists primarily of crustaceans, including pea crabs, benthic shrimp and swimming crabs and occasional takes small razor clams and fishes (Bizzarro 2005).

Life history parameters
Age at maturity: Female: 7 years (Timmons and Bray 1997); Male: 7 to 8.4 years (Timmons and Bray 1997).
Size at maturity (total length): Female: 99 cm TL (Timmons and Bray 1997), 66 cm TL (Villavicencio-Garayzar 1993), 87 cm TL (Dowton-Hoffman, 1996); Male: 91 to 100 cm TL (Timmons and Bray 1997), <63 cm TL (Villavicencio-Garayzar 1993), 80 cm TL (Dowton-Hoffman 1996), 92 cm TL (Dubois 1981), 110 cm TL (Talent 1985).
Longevity: 11 years (Timmons and Bray 1997).
Maximum size (total length): Females: 156 cm TL (Baxter 1966); Males: 114 cm TL (Dowton-Hoffman 1996).
Size at birth): 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), 17.5 cm TL in Sonora, Mexico (Márquez-Farías unpublished data).
Average reproductive age (years): Unknown.
Gestation time: 4 to 5 months in Sonora, Mexico (Márquez-Farías unpublished data).
Reproductive periodicity: Annual (Villavicencio-Garayzar 1993, Márquez-Farías unpublished data).
Average annual fecundity or litter size: 1 to 10 pups/litter (average 5) (Márquez-Farías unpublished data), 6–16 pups/litter (Villavicencio-Garayzar 1993).
Annual rate of population increase: Unknown.
Natural mortality: Unknown.

Systems:

Marine

Threats [top]

Major Threat(s):	Taken in directed artisanal fisheries in Mexico. 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 reveled a tendency to catch mature individuals by the fishery (Márquez-Farias in press). Neonates and small juveniles are not present in the directed fishery. Also taken as indirect landings by demersal trawls (especially shrimp trawlers), and gillnets in Mexican waters. The impact of high catches of mature individuals either by the directed artisanal fishery or in indirect landings is unknown. In the Bahía Almejas summer batoid fishery, this species is the most abundant in June landings (ca. 51% of catch, CPUE (#/vessel/day)=21.8) landings and third most abundant in August landings (ca. 13%, CPUE=2.8). The fishery in Bahía Almejas, Baja California has severely declined after greatly increased effort in the mid to late 1990’s and its abundance has almost surely declined in this region as a result of fishing pressure. In Sonora, Mexico, it is the most abundant batoid landed in the artisanal elasmobranch fishery (Hueter et al. unpublished data, Márquez-Farías 2002). Taken by anglers to a limited extent in US waters and occasionally sold in Asian markets in southern California. Habitat modification. Many embayments and estuaries in northwest Pacific Mexico are being modified to accommodate shrimp farming. Since this species uses these areas for feeding and reproduction, this could have a detrimental impact on its abundance in affected areas.

Major Threat(s):

Taken in directed artisanal fisheries in Mexico. 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 reveled a tendency to catch mature individuals by the fishery (Márquez-Farias in press). Neonates and small juveniles are not present in the directed fishery. Also taken as indirect landings by demersal trawls (especially shrimp trawlers), and gillnets in Mexican waters. The impact of high catches of mature individuals either by the directed artisanal fishery or in indirect landings is unknown. In the Bahía Almejas summer batoid fishery, this species is the most abundant in June landings (ca. 51% of catch, CPUE (#/vessel/day)=21.8) landings and third most abundant in August landings (ca. 13%, CPUE=2.8). The fishery in Bahía Almejas, Baja California has severely declined after greatly increased effort in the mid to late 1990’s and its abundance has almost surely declined in this region as a result of fishing pressure. In Sonora, Mexico, it is the most abundant batoid landed in the artisanal elasmobranch fishery (Hueter et al. unpublished data, Márquez-Farías 2002).

Taken by anglers to a limited extent in US waters and occasionally sold in Asian markets in southern California.

Habitat modification. Many embayments and estuaries in northwest Pacific Mexico are being modified to accommodate shrimp farming. Since this species uses these areas for feeding and reproduction, this could have a detrimental impact on its abundance in affected areas.

Conservation Actions [top]

Conservation Actions:	There are currently no specific conservation measures in place for this species in US or Mexican waters. In México, a moratorium on the allocation of additional elasmobranch fishing permits was enacted in 1993, but no formal management plan has been implemented for R. productus specifically or most other chondrichthyans in México. However, legislation is currently being developed in México to establish national elasmobranch fishery management. Elasmobranch landings in México are poorly monitored and lack species-specific details. All batoids are generally broadly termed “manta raya”. Improved clarity in catch records would provide an essential basis for detecting fishery trends and are needed throughout the species’ range. Expanded monitoring of directed elasmobranch catches and bycatch in México are necessary to provide valuable information on the population status of these rays. Fishery-independent surveys of this and other demersal elasmobranchs are also necessary to provide estimates of abundance and biomass. 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).

Conservation Actions:

There are currently no specific conservation measures in place for this species in US or Mexican waters.

In México, a moratorium on the allocation of additional elasmobranch fishing permits was enacted in 1993, but no formal management plan has been implemented for R. productus specifically or most other chondrichthyans in México. However, legislation is currently being developed in México to establish national elasmobranch fishery management.

Elasmobranch landings in México are poorly monitored and lack species-specific details. All batoids are generally broadly termed “manta raya”. Improved clarity in catch records would provide an essential basis for detecting fishery trends and are needed throughout the species’ range. Expanded monitoring of directed elasmobranch catches and bycatch in México are necessary to provide valuable information on the population status of these rays. Fishery-independent surveys of this and other demersal elasmobranchs are also necessary to provide estimates of abundance and biomass.

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:	Márquez, F., Smith, W.D. & Bizzarro, J.J. 2006. Rhinobatos productus. In: IUCN 2008. 2008 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 04 December 2008.
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