THE CONDITION FACTOR OF Mugil incilis HANCOCK (PISCES: MUGILIDAE) AND ITS SEASONAL CHANGES IN THE CIENAGA GRANDE DE SANTA MARTA (COLOMBIA)

Abstract

The annual variation in condition of the mullet Mugil incilis Hancock has been studied in the Ciénaga Grande de Santa Marta (CGSM), The largest coastal lagoon on the Colombian Caribbean, with emphasis on the influence of such environmental factors as salinity, temperature and trasparence of the waters on the condition of this species of Mugilidae. Seasonal differences observed in condition of M. incilis are evidently related to gonadal development and depend on food availability. The diet of M. incilis is based on detritus and its food supply seems to be very influenced by river discharge which also accounts for the salinity changes in the lagoon, this explains the inverse correlation (r = -0.82) found between salinity and condition of the mullets expressed as C = 0.9949 - 0.0057 S (°/oo). Annual salinity variation follows a rhythmic pattern of seasonal changes, not precisely "in situ", but in distant continental regions: the headwaters of the tributaries of the CGSM. These mullets spawn in Caribbean waters adjacent to the CGSM and their migration period (Dec-March) begins with their best physical condition, returning to their feeding areas in the CGSM 2 or 4 weeks later, until the end of the migration, with their lowest condition since these mullets apparently do not feed at all during the spawning migration. No change related to temperature variations was observed, and turbid waters were the rule in M. incilis feeding sites.