The Pacific Sharpnose Shark (Rhizoprionodon longurio) is a warm temperate and tropical species that occurs from the intertidal to 27 m over soft mud and sand on the continental shelf (Springer 1964, Compagno 1984). Trends in R. longurio landings from Sinaloa and the Gulf of California, Mexico indicate marked seasonal movement patterns (Castillo-Géniz 1990, Márquez-Farías et al. 2005, Hueter et al. unpubl. data). The species is a primary component of artisanal elasmobranch fisheries during the Winter (January, February) and Spring months (March, April, May) but is not captured during the Summer and Autumn, when it is believed to move into deeper waters and possibly into the central Gulf of California (Kato and Hernández 1967, Márquez-Farías et al. 2005). A tagged specimen was reported by Kato and Hernández (1967) to have travelled from the southern tip of the Baja California peninsula, north 600 miles along the Pacific coast of Baja California.

This species segregates by size and sex (Castillo-Géniz 1990). The northern Gulf of California and the Sonora coast may serve as an important pupping area for the Mexican Pacific population (Bizzarro et al. 2000). It is uncertain whether open coastal areas or estuaries are used for pupping grounds.

The maximum reported total length (TL) of 154 cm was recorded from Peru (Hildebrand 1946), but specimens from Mexico and Colombia are rarely observed at greater than 120 cm TL (Franke and Acero 1991, Márquez-Farías et al. 2005). Size at birth varies between 30 to 37 cm TL (Springer 1964, Compagno 1984, Bizzarro et al. 2000, Márquez-Farías et al. 2005).

Castillo-Géniz (1990) reported that males mature at 93 cm TL and females at 83 cm TL. Earlier studies, however, report that males mature at 58?69 cm TL (Springer 1964, Compagno 1984) and that females are mature at 103 cm TL (Compagno 1984). Estimates of fecundity based on the number of embryos per female range between one and 12, with an average of 7.4 pups per litter (Márquez-Farías et al. 2005).

The gestation period is likely to be 10?12 months (Castillo-Géniz 1990, Márquez-Farías et al. 2005). Evidence of a potential resting period has been provided by Márquez-Farías et al. (2005), indicating that the species may possess a two year reproductive cycle. However, in the central Mexican Pacific (Nayarit coast) and in the upper Gulf of California gravid females with near-term embryos and postpartum females with extended uterus with oocytes close to being ready for ovulation have been reported. This suggests that the species has an annual cycle (Pérez-Jiménez et al. 2005), but further research is required to confirm this.

Congeners, including R. taylori and R. terraenovae, have been reported to possess a comparatively greater intrinsic rate of increase, faster growth, and higher fecundity than many elasmobranchs (Márquez-Farías and Castillo-Géniz 1998, Simpfendorfer 1999). It is possible that R. longurio may also be a moderately productive species. The diet of this species is dominated by teleosts and includes, to a lesser extent, cephalopods and crustaceans (Castillo-Géniz 1990, Márquez-Farías et al. 2005).

Red List Category

Red List Criteria

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Locally very abundant (Compagno et al. 2005), but no other information is available.

Unknown

Major threats include bycatch in trawl and other artisanal fisheries using gillnets, longlines, or traps, as well as directed artisanal fisheries for elasmobanchs. This species is taken in directed artisanal elasmobranch fisheries throughout the Gulf of California and Mexican Pacific using bottom set gillnets and longlines (W.D. Smith, J.F. Márquez-Farias and J.C. Pérez-Jiménez pers. obs.). Industrial trawl fisheries for shrimp are generally intense in areas of the Eastern Central and Southeast Pacific.

Artisanal net fisheries operate across the species? South American range, and although species-specific data are not available, the Pacific sharpnose shark is likely captured by inshore fisheries in Colombia, Ecuador and Peru. In Peru, pressure on inshore shark species is high, particularly houndsharks (family Triakidae), but it is likely that this shark is also a component of landings there.

Peak landings have been recorded from the Gulf of California and Sinaloa during the winter and spring months. The species? movement patterns, combined with changes in directed fishery effort result in relatively small landings during the rest of the year. Large juveniles and adults dominate the catches of Sinaloa and the northern Gulf of California but all size classes are present among artisanal landings (Bizzarro et al. 2000, Márquez-Farías et al. 2005). Some anecdotal evidence suggests that landings of this species may have decreased in some artisanal fisheries (W.D. Smith, J.F. Márquez-Farias and J.C. Pérez-Jiménez pers. obs.). As the northern Gulf of California and the Sonora coast may serve as an important pupping area for the Mexican Pacific population, fisheries operating in this area may pose a specific threat to the population.

Other human factors, particularly water pollution, probably impact this species and its inshore habitat in heavily populated areas.

A moratorium on the issue of elasmobranch fishing permits was issued in 1993, but no formal management plan has been implemented for R. longurio specifically or most other chondrichthyans in Mexico. However, legislation is currently being developed in Mexico to establish national elasmobranch fishery management.

Elasmobranch fisheries are unmanaged throughout Central America, and attempts to regulate fisheries in Central America would greatly improve conservation of R. longurio and other chondrichthyans. Proposed measures would include a ban on shark finning and protection of specific shark species.

Monitoring of any fishing in the northern Gulf of California and the Sonora coast is required to ensure there is no extensive removal of pups. Improved clarity in catch records would provide a basis for detecting potential trends in effort and landings. In addition to species-specific catch details, life history information including age, growth, longevity, and further reproductive studies are required.

There is also a requirement to obtain information on catches where little or no data are available (i.e., South America).