Growth and population structure of Argopecten purpuratus at La Rinconada Marine Reserve, Antofagasta, Chile

Abstract

Se presentan los parámetros de crecimiento L ∞ = 120.38 mm y K = 0.9668 para el banco de Argopecten purpuratus de la Reserva Marina La Rinconada (Antofagasta, Chile), obtenidos entre marzo de 2001 y mayo de 2003 usando métodos de marcaje y recaptura de ejemplares. La elevada recaptura de individuos marcados (60-80%) indica baja mortalidad natural y una conducta sedentaria del recurso. Las evaluaciones anuales realizadas para estimar el tamaño del banco confirmaron tal conducta, encontrándose la mayoría de los individuos agregados en el centro, con densidades que variaron entre años de 9 a 14.8 ind m-2 .

Evidence of clandestine harvest and failure of conservation policies for Argopecten purpuratus in the Rinconada Marine Reserve (Chile)

“…The surface area colonized by scallops was delimited by buoys set by hookah divers; the buoy positions were recorded using a GPS (Garmin 12 XL). The total surface area occupied by scallops was determined using a Zeting KP‐27 plane planimeter (Avendaño & Cantillánez, , ). A pilot sampling was then undertaken within the scallop bed to determine the minimum number of samples required to estimate A. purpuratus density and total abundance.…”

“…Indeed, this population generates large quantities of spat into artificial collectors on a sustainable basis (Avendaño, Cantillánez Silva, & Peña Forner, ; Avendaño, Cantillánez, & Thouzeau, ; Cantillánez, ; Cantillánez Silva et al, ), owing to year‐round reproductive activity and larval retention within the bay (gyre circulation). Fishing closure and favourable oceanographic conditions provided by the 1997–1998 ENSO event promoted an increase in scallop abundance within the reserve, from 6.1 × 10 6 ind in 1997 to 11.3 × 10 6 ind in 1999 (Avendaño & Cantillánez, ). Although a huge decline in scallop abundance was observed in subsequent years, mainly due to illegal harvesting, scallop losses were partly compensated by constant spat settlement within the reserve (Avendaño & Cantillánez, ).…”

“…Fishing closure and favourable oceanographic conditions provided by the 1997–1998 ENSO event promoted an increase in scallop abundance within the reserve, from 6.1 × 10 6 ind in 1997 to 11.3 × 10 6 ind in 1999 (Avendaño & Cantillánez, ). Although a huge decline in scallop abundance was observed in subsequent years, mainly due to illegal harvesting, scallop losses were partly compensated by constant spat settlement within the reserve (Avendaño & Cantillánez, ).…”

Artificial collection and early growth of spat of the scallop <i>Argopecten purpuratus</i> (Lamarck, 1819), in La Rinconada Marine Reserve, Antofagasta, Chile

“…These reductions may have been due to the decrease in the abundance of the adult broodstock on the scallop bed, which produces the gametes supporting its reproductive processes. The broodstock numbers on the bed, reduced by harvesting, declined from 2.6 million individuals in March 2001 to 930000 individuals in May 2002 Avendaño and Cantillánez, 2005).…”

“…This reproductive process generates a continuous presence in the area of larvae of this species, whose periods of greatest abundance are directly related to the periods of the highest reproductive activity (Cantillánez, 2000;Cantillánez et al, 2001;Avendaño et al, 2006). The continuous presence of these larvae in the plankton of the Reserve is due to the presence of current gyres in the area which lead to a high capacity for retention of particulate matter within an area about 5 km in diameter, favouring continuous natural settlement of postlarvae on the bottom and/or into artificial collectors placed in the environment (Cantillánez, 2000;Cantillánez et al, 2001;Avendaño and Cantillánez, 2005;Avendaño et al, 2006).…”