SPATIAL AND TEMPORARY VARIATION OF JUVENILES OF PINCTADA IMBRICATA (RÖDING, 1798) AND ARGOPECTEN NUCLEUS (BORN, 1778) IN THE NORTH OF THE COLOMBIAN CARIBBEAN

Abstract

In order to know the response of this group of organisms to changes in hydrographic conditions, spatial (regions, bays, depths) and temporal (climatic periods) variation in the juveniles abundance of two species with potential economical use in the northern Colombian Caribbean region was assessed. This variation was determined from 1994 to 1996, by the fixation of individual in artificial collectors in the Tayrona National Park (PNNT) and comparing the abundance of juveniles in Concha Bay and Chengue bay at depths of 5, 10, 15 and 20 m. Differences between bays and depths were found; Chengue Bay at 5 m had the highest average abundance of Pictada imbricata (145 individuals per collector). Differences between climatic periods were also registered; for the first species the highest number of individuals were collected during the dry period –first semester of the year, which is characterized by the presence of upwelling waters. The abundance of Argopecten nucleus had a lower abundance and an undefined recruitment pattern. From 1997 to 1998 the abundance of juveniles between the PNNT and La Vela Cape (CV) was compared finding significant differences between these regions; the average abundance of P. imbricata (61 ind/col), was greater in the PNNT while individuals of A. nucleus (23 ind/col) were more abundant in the CV. At the temporal scale, these species presented differences in both regions. The first two exhibited a defined pattern in the PNNT with more dominance in the dry period of the year; A. nucleus showed great variation in the PNNT while in the CV they were dominant in the dry period. According to these results, the optimal conditions for recruitment of A. nucleus are given in the CV region during the dry period, and P. imbricata in the region of PNNT during the dry period. The temperature was related with abundance of P. imbricata en el CV and A. nucleus with visibility. Nevertheless, the highest number of juveniles was observed during a specific climatic period in which the environmental variables have well defined characteristics.