Rhizoprionodon Longurio Research Articles

Activities and Catch Composition of Artisanal Elasmobranch Fishing Sites on the Eastern Coast of Baja California Sur, Mexico

Eighty–three artisanal fishing sites were documented from seasonal surveys of the Gulf of California coast of Baja California Sur conducted during El Niño (1998) and La Niña (1999) conditions. The direct targeting of elasmobranchs was observed at approximately half (48.2%) of these sites. Sharks numerically dominated sampled landings (71.3%, n = 693), and exceeded those of batoids during all seasons. Among the primary species in observed landings were the scalloped hammerhead, Sphyrna lewini (15.2%, n = 148), Pacific angel shark, Squatina californica (11.6%, n = 113), blue shark, Prionace glauca (11.4%, n = 111), Pacific sharpnose shark, Rhizoprionodon longurio (11.3%, n = 110), and pygmy devil ray, Mobula munkiana (8.6%, n = 84).

Total mercury content found in edible tissues of top predator fish from the Gulf of California, Mexico*

Fish at the top of the food chain bioaccumulate and biomagnify toxic metals including mercury (Hg), at a higher rate than nonpredatory fish. However, although some top predator fish species are important in the human diet, the risks for consumers in Mexico are difficult to evaluate due to the scarce baseline information available. In the present article, data on the total mercury (THg) concentrations found in edible tissues of different species of sharks, rays, large pelagic fishes and groupers from the Gulf of California are presented and compared with national and international health guidelines. During 2003 and 2004, 73 shark dorsal tissue samples, 52 ray samples, 66 large pelagic fish samples and 16 grouper samples were collected at different sites along the Gulf of California. Samples were digested in a microwave system and analyzed by cold vapor atomic absorption spectrophotometry. Thirty samples (14%) showed concentrations of Hg above the national statutory limit of 1 mg kg−1, from which 25 samples were sharks and 3 were large pelagic fishes. A positive correlation was found between the natural log of THg [ln(THg)] and total length (TL cm) in species of sharks, rays and groupers. The Teacapán estuary in Sinaloa was detected as a possible source of Hg into the Gulf of California due to historic mining in the watershed. Mean Hg concentrations exceeded the regulatory limit of 1 mg kg−1 in the following highly commercial shark species: smooth hammerhead, pelagic thrasher, pacific sharpnose shark, dusky shark, scalloped hammerhead, and whitenose shark, in that order. It is recommended that preventive food advisories be issued with respect to these species until further investigations are conducted. The authors certify that the following paper has not been published elsewhere and it has not been submitted simultaneously for publication elsewhere.

Artisanal Shark Fishery at "Tres Marias" Islands and Isabel Island in the Central Mexican Pacific

There is a lack of basic biological information on the shark species caught in the region around the Tres Marias Islands and Isabel Island in the Central Mexican Pacific. Intensive monitoring was undertaken from October 1995 to March 1996 of shark landings by the artisanal fleet at La Cruz de Huanacaxtle, Nayarit, that fished south of Tres Marias Islands and, from November 2000 to February 2001, of landings by another fleet that fished around Isabel Island and close to the Tres Marias. Smooth hammerhead Sphyrna zygaena (35%), silky shark Carcharhinus falciformis (27%) and blue shark Prionace glauca (25%) were the most important species of 2 004 sharks observed at La Cruz de Huanacaxtle. At Isabel Island, the most important species of 7 464 sharks sampled were S. lewini (49%) and Pacific sharpnose shark Rhizoprionodon longurio (45%). This paper describes the shark species caught at these islands, the catch per unit effort of the principal species throughout the fishing season, their length frequency distributions and percent mature, and gear selectivity issues.

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

Observations on the Biology of the Pacific Sharpnose Shark (<i>Rhizoprionodon longurio</i>, Jordan and Gilbert, 1882), Captured in Southern Sinaloa, México&gt;