Reproductive cycle of Argopecten purpuratus (Bivalvia: Pectinidae) in La Rinconada marine reserve (Antofagasta, chile):: Response to environmental effects of El Nino and La Nina

Gonadosomatic index (GSI) and ovarian histology were used to determine the seasonality, amplitude, and magnitude of spawnings of the Argopecten purpuratus population within the marine reserve at La Rinconada, Chile, between December 1995 and February 2000. In general, spawnings occurred most of the year without prolonged periods of reproductive inactivity. Studies of this population throughout warm and cold oceanographic phenomena such as the El Nino-Southern Oscillation (ENSO) event of 1997-1998 and the La Nina event of 1998-2000 showed that the reproduction of this population occurred mainly between September and April, declining in the winter months from June through August, during which a period of sexual quiescence was observed in some individuals. An intense reproductive activity in the population, following the 1997-1998 warmer period, extended over the whole year. Histological analysis of the female portion of the gonad confirmed the GSI results and demonstrated the presence both of acini which appeared to be mature and other acini with various degrees of atresia and/or oocyte lysis. The study also revealed spawning asynchrony in this species and the presence of various stages of maturity within the same individual. Periods of high reproductive activity were correlated with strong diurnal temperature fluctuations and rises in phaeopigment concentration and phytoplankton cell counts, suggesting that these factors could be triggers for Argopecten spawning. These new insights on the reproductive cycle and conditioning of A. purpuratus would facilitate future management practices on the timing of artificial collectors and spat collection. (c) 2005 Elsevier B.V. All rights reserved.