Horizontal and vertical movements of the scalloped hammerhead shark, Sphyrna lewini, in the southern Gulf Of California, Mexico

Abstract

Recibido en enero de 1992; aceptado en julio de 1992 RESUMENSe proporciona una descripción de los movimientos horizontales y verticales de cuatro tiburones martillo (Sphyma lewini) marcados con transmisores ultrasónicos.El estudio se llevó a cabo en aguas pelágicas que rodean el Bajo Espíritu Santo y la Isla Las Animas, ubicados en el sur del Golfo de California, durante los meses de agosto de 1986, agosto de 1988 y julio y agosto de 1989. Se observó que los tiburones se mantuvieron generalmente sobre el bajo durante el día. Se realizaron quince seguimientos telemétricos de los movimientos de salida y regreso (homing) al bajo. De estos rastreos, trece se llevaron a cabo hacia la región pelágica durante la noche y dos de día. El intervalo de distancia máxima alcanzada fue de 4 a 20 km. Algunos movimientos de salida y regreso fueron próximos y paralelos uno del otro, lo que sugiere que estos tiburones tienen rutas designadas para visitar sus sitios preferencialesde alimento. Los tiburones presentaron movimientos verticales, ascendentes y descendentes (similares a la trayectoria de un yoyo). El intervalo de profundidad de las inmersiones observadas fue de 50 a 450 m. Los movimientos verticales se llevaron a cabo generalmente por debajo de la capa mixta superficial y por encima del fondo marino. Las diferencias de las temperaturas del agua (20 a 6oC) en que se desplazaron los tiburones durante sus excursiones verticales fueron pequeñas en relación con las observadas en otras especiesde peces, lo que sugiere que para el tiburón martillo la función de dichas excursiones no es de termorregulación. August 1986, 1988-1989, and July 1989 in the pelagic environment surrounding Espíritu Santo Seamount and Las Animas Island in the southem Gulf of California. 'I'he hammerheads generally remained above the seamount and near the island during the day. Fífteen sharks were tracked during homing movements away from and back to the seamount. Of the excursions, 13 were made into the pelagic region during the night and two during the day. The maximum distance moved away from the seamount ranged from 4 to 20 km. Departure and retum movements were at times close to and parallel to each other, suggesting that the sharks followed particular routes to preferred feeding sites. The sharks made vertical excursions, ascending and descending in the water column (in yo-yo form). The diving oscillations occurred behveen SO to 4.50 m. These vertical movements were usually below the surface mixed layer and well away from the bottom. The range in water temperatures (2o-6oC) encountered during these vertical excursions was small in relation to that reoorted for other species of fishes, suggesting that for this species the function of the excursions may not be thermoregulation.

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

“…CPUE for S. lewini was higher in both drift gillnet with 15-20 cm mesh size and bottom longline with 60 mm J hooks, possibly because this species carries out vertical movements (Klimley et al, 1993).…”

Spatial and temporal movement patterns of a multi-species coastal reef shark aggregation

“…Aggregations have been documented in many shark taxa, including planktivores (Sims & Merrett 1997, Meekan et al 2006), large predators (> 4 m) (Weng et al 2007), coastal species (Klimley & Nelson 1981, Dudley et al 2005) and reef-associated sharks (Stevens 1984, McKibben & Nelson 1986, Gruber et al 1988, Economakis & Lobel 1998, Smith & Pollard 1999, Pratt & Carrier 2001, Whitney et al 2004, Hight & Lowe 2007. Aggregations have been observed in both adult and juvenile size classes for some species (e.g.…”

Ontogenetic migration of a female scalloped hammerhead shark Sphyrna lewini in the Gulf of California

“…Current understanding of the ontogenic migration of the scalloped hammerhead shark in the Gulf of California is based largely on the incidental take of juveniles and stomach content analyses from a relatively small number of individuals [14,15]. Furthermore, the seasonal change in abundance of scalloped hammerhead shark landings by artisanal fishermen [16] and seasonal presence of large schools at volcanic islands and seamounts [14,17], suggest that this species migrates away from this region but returns to the same locations annually. However, actual migratory pathways have yet to be identified for this species.…”