|Scientific Name:||Rhinoptera steindachneri|
|Species Authority:||Evermann & Jenkins, 1891|
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Assessor/s:||Smith, W.D. & Bizzarro, J.J.|
|Reviewer/s:||Kyne, P.M., Fowler, S.L. & Compagno, L.J.V. (Shark Red List Authority)|
Rhinoptera steindachneri is the only representative of its family known from the eastern Pacific. Little is known of the species? ecology yet it is one of the primary components of artisanal elasmobranch fisheries in the Gulf of California and the southern Pacific coast of the Baja peninsula (México). As a broadly distributed, migratory species inhabiting shallow coastal waters, it is likely an important component of artisanal fisheries throughout its range. The extent of movements throughout the eastern Pacific coast, longevity, growth rates, population structure, and age at maturity are unknown. Both sexes mature at similar sizes that are approximately 70% of their maximum size, suggesting that the species may have a relatively late age at maturity. The reproductive strategy of producing a single pup following an extended 10?12 month gestation period indicates that the species has a low productivity and is likely to be highly susceptible to overexploitation. Due to such low fecundity, fishing pressure and its important contribution to artisanal fisheries, R. steindachneri is considered to be Near Threatened throughout its range. An assessment of the species? current population status and monitoring of catches throughout its range is of priority.
|Range Description:||The range of R. steindachneri has been reported from Bahía de Sebastian Vizcaino, central Baja California, México, (Castro-Aguirre and Espinosa-Peréz 1996), through the Gulf of California (McEachran and Notarbartolo di Sciara 1995), and south to Peru (Chirichigno 1974) and the Galapagos Islands (Ecuador) (Grove and Lavenberg 1997).|
Native:Colombia; Costa Rica; Ecuador; El Salvador; Guatemala; Honduras; Mexico; Nicaragua; Panama; Peru
|FAO Marine Fishing Areas:||
Pacific – eastern central; Pacific – southeast
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||No information on population estimates, subpopulations, degree of fragmentation, or general abundance are available for this transient species.|
|Habitat and Ecology:||
Rhinoptera steindachneri is widely distributed throughout shallow inshore waters of the eastern subtropical and tropical Pacific. It is typically found in waters ranging from intertidal depths to 25 m, but has been recorded to 65 m (Bizzarro et al. submitted). It is usually associated with sandy bottoms but also occurs near rock or coral reefs, often near the reef dropoffs (Michael 1993). A transient, highly mobile species it often forms large schools or moves in loose aggregations. Its movements may be related to water temperature, as it tends to migrate northward in the Gulf of California during the spring and south in the autumn (Bizzarro et al. submitted). The reproductive mode of this species is aplacental viviparity. Females nourish young initially by means of a yolksac and later supplement this energy source with protein-rich uterine excretions termed hisotrophe. Only a single ovary is functional. In the northern Gulf of California and Bahía Almejas on the Pacific coast of México?s Baja peninsula males and females reach maturity at similar sizes. Median size at 50% maturity is estimated as 70.0 cm disc width (DW) in females and 69.9 cm DW in males (Bizzarro et al. submitted). The smallest female reported as mature was 65cm DW and the largest immature specimen measured 72 cm DW (Bizzarro et al. submitted). Maturity among males ranges 64 to 78 cm DW (Bizzarro et al. submitted). Females give birth to a single pup during late June and July following an estimated gestation period of 10 to 12 months (Bizzarro et al. submitted). Courtship and fertilization follows shortly after parturition (Bizzarro et al. submitted). Rhinoptera steindachneri possess plate-like teeth that are highly specialized for crushing and grinding hard-bodied prey items such as molluscs.
Life history parameters
Age at maturity (years): Unknown.
Size at maturity (disc width): Median size at 50% maturity: 70.0 cm DW (Bizzarro et al. submitted) (female); Median size at 50% maturity: 69.9 cm DW (Bizzarro et al. submitted) (male).
Longevity (years): Unknown.
Maximum size (disc width): 104 cm DW (female); 96 cm DW (male) (Bizzarro et al. submitted).
Size at birth: 39 to 43 cm DW (Bizzarro et al. submitted).
Average reproductive age (years): Unknown.
Gestation time: 10 to 12 (Bizzarro et al. submitted).
Reproductive periodicity: Annual (Bizzarro et al. submitted).
Average annual fecundity or litter size: 1 (Bizzarro et al. submitted).
Annual rate of population increase: Unknown.
Natural mortality: Unknown.
Directed artisanal elasmobranch fisheries. Rhinoptera steindachneri is one of the most common batoid species landed in both the northern Gulf of California (GOC) and Bahía Almejas, Baja California Sur, México, where it is taken almost exclusively with bottom set gillnets, but may be landed in nearshore surface gillnets and longlines as well (Bizzarro et al. submitted, Notarbartolo di Sciara 1987). In the northern GOC from 1998?1999, R. steindachneri was most frequently observed in summer landings (11.4% of catch, CPUE=8.0 individuals/vessel/trip) and was rarely noted in winter (0.1%, CPUE=0.1). In Bahía Almejas from 1998?2000, it was more abundant in August (5.15%) than in June landings (0.30%), a trend also evident in CPUE (August=1.13, June=0.13). The mean size of female R. steindachneri captured in the GOC was 64.4 + 11.8 cm DW (mean and SD) whereas males averaged 64.2 + 14.0 cm DW (Bizzarro et al. submitted).
Also taken as incidental catch among trawl (especially shrimp trawlers) and other artisanal fisheries using gillnets and longlines in México. No information is currently available on its presence or contribution to artisanal fisheries throughout the rest of its range, however, given its inshore habitat and the occurrence of fishing activities in coastal zones throughout its range it is most certainly commonly taken.
Habitat modification. Many embayments and estuaries in north-west Pacific México 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.
Rhinoptera steindachneri fisheries are generally unmanaged throughout the species range. In México, a moratorium on the issue of elasmobranch fishing permits was enacted in 1993, but no formal management plan has been implemented. However, legislation is currently being developed in México to establish national elasmobranch fishery management. Elasmobranch fisheries are generally unmanaged throughout Central and South America. Attempts to monitor and regulate fisheries in the eastern tropical Pacific would greatly improve conservation of R. steindachneri and other chondrichthyans.
Elasmobranch landings reported from México and Central America typically lack species specific details. Most often, all batoids are often simply termed ?manta raya? collectively. Improved clarity in catch records would provide an essential basis for detecting fishery trends and are much needed throughout the species? range. Expanded monitoring of directed elasmobranch landings and bycatch in México, Central, and South America are necessary to provide valuable information on the biology and population status of these rays. Fishery-independent surveys of this and other elasmobranchs are necessary to provide estimates of abundance and biomass. Due to the transient nature of this schooling ray, coordinated national and international efforts are necessary to adequately assess movements, abundance, and fishery impacts.
In addition to species-specific catch details, life history information including age, growth, longevity, movement patterns, habitat use, potential nursery areas, diet, and further reproductive studies are necessary to develop effective conservation actions for R. steindachneri. Direct estimates of fishing and natural mortality are critical for assessing fisheries impacts on a particular species. Tagging, tracking, and genetic studies are essential for determining the population structure, movement patterns, and possible subpopulations throughout the species? range.
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 region. See Anon. (2004) for an update of progress made by nations in the range of R. steindachneri.
|Citation:||Smith, W.D. & Bizzarro, J.J. 2006. Rhinoptera steindachneri. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 18 May 2013.|
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