Observations on the Biology of the Pacific Sharpnose Shark (Rhizoprionodon longurio, Jordan and Gilbert, 1882), Captured in Southern Sinaloa, México>

Abstract

The Pacific sharpnose shark, (Rhizoprionodon longurio, Jordan and Gilbert, 1882), migrates along the Pacific coast of Mexico. It is captured with gillnets and bottom long lines commonly used in the artisanal fishery of Mazatlan. From a sample of 3 464 individuals, R. longurio was observed to be a viviparous shark of small size, which is born at an average length of 31 cm total length (TL), after a gestation period of 10 to 11 months. The number of embryos showed no statistical relationship to the TL. The average number of embryos per female was 7.4 (σ = 2.01, n = 146) and sex ratio was 1:1. Observations on the growth of the claspers indicated that male maturity begins at 93 cm TL. The two smallest gravid females measured were 83 and 87 cm TL. The rest of the gravid females were at least 92 cm TL. Between 90 and 95 cm TL, the females exhibited an increase in the width of the oviducal gland and its size ranged from 5 to 12 mm. The statistical relationship between weight and length is presented in which females reach a larger size than males. The diet of R. longurio was composed principally of crustaceans and demersal teleost fishes.

Stomach contents of the Pacific sharpnose shark, Rhizoprionodon longurio (Carcharhiniformes, Carcharhinidae) in the southeastern Gulf of California

“…longurio has been considered a generalist predator by all authors who described its feeding habits (Saucedo-Barrón et al, 1982;Castillo et al, 1996;Alatorre-Ramírez, 2003;Márquez-Farías et al, 2005), but the low value of Levin's index obtained in this study suggests the feeding behaviour of a specialist predator. However, as is the case for electivity indices which may be influenced by external food availability (Strauss, 1979;Gras & Saint-Jean, 1982), this is probably due to a high dominance in the pelagic community of the more frequent and abundant prey items found in the stomachs of this species.…”

“…In particular, information on its feeding habits is limited (Márquez-Farías et al, 2005) and is mostly confined to grey literature (Saucedo-Barrón et al, 1982;Alatorre-Ramírez, 2003;Conde-Moreno, 2009). Aiming to add information on its feeding ecology in the SE Gulf of California, we determined the stomach contents of specimens of this species caught by the artisanal fishing fleet operating off Mazatlán, Sinaloa, and NW Mexico.…”

“…Its distribution ranges from California to Peru (Compagno, 1984), it is exploited by the artisanal fishing fleets operating along the Mexican coasts from Baja California to Chiapas, and it appears in the bycatch of industrial trawl fisheries (Márquez-Farías et al, 2005).…”

Panbiogeographical analysis of the shark genus Rhizoprionodon (Chondrichthyes, Carcharhiniformes, Carcharhinidae)

“…The cold currents appear to constitute an ecological barrier to Rhizoprionodon , restricting its distribution to the tropical waters. For instance, the individual track of R. longurio unexpectedly bounds the cold California Current, probably as a result of the winter to spring and summer to autumn migration scheme verified by Márquez‐Farias et al (2005). According to these authors, the catch of R. longurio in this region shows a strong seasonal pattern, due to the massive movement of the species associated with changes in sea temperature.…”

Gillnet selectivity of the Indian oil sardine Sardinella longiceps fished in the Sea of Oman

“…This could not be achieved in this study as this would have reduced sample sizes to unacceptably low numbers. Márquez-Farias et al (2005) added oceanographic currents as a possible factor affecting selectivity; since strong currents can distort the shape of the meshes and therefore select for fish sizes not captured under conditions of a mild current. This effect was considered negligible in this study.…”