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Revista de biología marina y oceanografía

On-line version ISSN 0718-1957

Abstract

ALEJO-PLATA, Carmen; GOMEZ-MARQUEZ, José L; RAMOS, Samuel  and  HERRERA, Eduardo. Presence of neonates and juvenile scalloped hammerhead sharks Sphyrna lewini (Griffith & Smith, 1834) and silky sharks Carcharhinus falciformis (Müller & Henle, 1839) in the Oaxaca coast, Mexico. Rev. biol. mar. oceanogr. [online]. 2007, vol.42, n.3, pp.403-413. ISSN 0718-1957.  http://dx.doi.org/10.4067/S0718-19572007000300020.

The Oaxaca coast in Mexico has a narrow continental shelf and it reaches depths greater than 500 meters near the coast; furthermore it consists of bays and sheltered areas, where high food availability is found. Each week, from March 2001 to December 2005, the unloading areas of artisanal fisheries between the bays of Huatulco and Puerto Escondido in the Oaxaca coast were visited. Data on fishing gear and zones, as well as the species composition of the captures were taken. In the zone, three fishery units operated: shark, pelagic and demersal. All three capture sharks in a direct or incidental way. At the studied region, 419 organisms of S. lewini were registered; from August to September newborn individuals (43.9%, 44 to 64 cm of total length), young of the year (9.3% 65-75 cm Tl) and juveniles (30.3%, 75 to 168 cm Tl) were observed; pregnant females were registered in March, May and June with a fecundity ranging from 18 to 24 embryos (35 to 45 cm Tl). With respect to C. falciformis, 1314 individuals were registered. Newborns (4.7%, 65-71 cm Tl) and young of the year (3.8%, 72 to 80 cm Tl) were observed from January to September; juveniles (65.4%, 80 to 170 cm Tl) were captured throughout the year; from January to November, 52 pregnant females were observed with embryos at different developmental stages. The presence of newborns, young of the year and pregnant females with embryos in advanced development condition, suggest that the coastal waters near the shoreline of the Oaxaca coast are a spawning and nursery area for these shark species

Keywords : shark; newborns; young of the year; nursing area; Pacific.

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