Abstract
Artificial collection of early juveniles (“spat”) of the scallop Argopecten purpuratus in Japanese-type collectors was evaluated between January 2001 and July 2002 in the La Rinconada Marine Reserve, Antofagasta, Chile. This area of Antofagasta Bay has in the past been noted for the retention of scallop larvae by local gyres, in which their numbers can vary between 89 and 34175 larvae m -3 , producing larval sets of 400 to 15340 post-larvae (spat) per collector. The results showed no quantitative relationship between larval abundance in the water and the spat density collected per day in the collectors, although high settlement rates were associated with high numbers of umboned larvae in the water. Allowing collectors to remain in situ for extended periods of 88 and 159 days resulted in a severe loss of seed which had settled in the collectors during the first 28 to 40 days of immersion. These losses varied between 50.9 and 99.6% of the spat collected, and were more prejudicial for the smaller cohorts that had settled in the collectors at the end of the first immersion period. The growth rates measured among different cohorts for each immersion period varied between 81.3 and 235.2 mm/day for the first cohort (C 1 ) and between 64.0 and 167.4 mm/day for the second cohort (C 2 ). The highest growth rates occurred in collectors containing the lowest numbers of spat after the occurrence of spat losses during the long periods of immersion. Occurrence of intraspecific competition within the collectors is discussed as potentially responsible for the decreases in spat numbers and the variations observed in their growth rates.
Highlights
One of the main beds of the scallop Argopecten purpuratus on the Chilean coast is located at the northern end of Antofagasta Bay (La Rinconada) in northern Chile at 23o28’S; 70o30’W
This study presents data related to the larval cycle and settlement of postlarval scallops in artificial collectors, as well as the growth and recovery of the spat maintained in the collectors at sea for extended periods of time
Settlement of postlarvae of A. purpuratus was continuous in the Reserve from January 2001 to May 2002
Summary
One of the main beds of the scallop Argopecten purpuratus on the Chilean coast is located at the northern end of Antofagasta Bay (La Rinconada) in northern Chile at 23o28’S; 70o30’W This bed, occupying an area of about 270 ha, has become extremely important in basic and applied research on this scallop, and was protected by the establishment of the La Rinconada Marine Reserve by Supreme Decree N° 522 of the Chilean government in September 1997. Coastal upwelling processes produce phytoplankton peaks throughout the year, with values for chlorophyll a varying from a minimum of 0.6 μg l-1 to a maximum of 24.8 μg l-1 (Rodríguez et al, 1991; Cantillánez, 2000; Avendaño et al, 2004)
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