Argopecten purpuratus (Mollusca, Pectinidae) post-El Niño 1997-98 response in La Rinconada Marine Reserve (Antofagasta, Chile)

From 1999-2001, the Argopecten purpuratus population at La Rinconada was directly evaluated by monitoring larvae and their subsequent settlement on artificial collectors to determine their density, size structure, and abundance. An increase in specimens, doubling the number observed in 1997, occurred in 1999. However, reductions in the distribution area, specimens, and average size occurred in 2000 and 2001, reflecting anthropogenic impacts. Application of the growth parameters to the annual size structure indicated losses of 5.7 million individuals between 1999 and 2000 and 5 million between 2000 and 2001. The specimens increase over 90 mm, from 130,000 in 1997 to 2.6 million in 2001, explains the high larvae numbers found, with records of 17,667 and 21,756 in 1999; 16,100 in 2000; and 34,175 and 21,700 in 2001. A relationship between larval presence and postlarval settling could not be established; only the relationships between periods of larval abundance and those of maximum fixation could be observed. In conclusion, a viable solution to illegal fishing affecting the reserve with complementary or substitute measures for local fishers is urgently required.