Seasonal patterns of three fish species in a Caribbean coastal gill-net fishery: Biologically induced or climate-related aggregations?

Although both seasonal patterns and short-term variation in CPUE are known to occur in most fisheries, particularly small-scale coastal fisheries, the analysis of their underlying factors have received little attention to date. When these factors become part of the local fishermen's ecological knowledge, the resulting peak abundances are often intensively fished, as a result of their predictability, both in space and time. This study, conducted in the Caribbean Sea of north-eastern Colombia, tests hypotheses derived from local fishermen of seasonal patterns of the demersal species Lutjanus analis and the two pelagic species Caranx crysos and Scomberomorus cavalla, and of the possible wind- or swell-driven aggregations of L. analis. ARIMA modelling and Fourier analysis were used to identify seasonal patterns from time series of monthly mean catch per unit effort. Available biological information and, concerning L. analis, also data on wind speed and significant wave height anomalies were used to analyse the intra-annual patterns. Evidence of biologically induced seasonal migrations was found for the two pelagic species. Concerning L. analis, in the windy season the timing of these aggregations and therefore peak CPUE values appear correlated with the wind forcing occurring a few days before, but in the last months of the wet season these peak abundances seem to be mainly related to pre-spawning migrations and spawning aggregations. Thus, we state that both kinds of events should be taken into account for the implementation of precautionary measures aimed to reduce the vulnerability to overfishing of these aggregations.