Spatio-temporal variations of the catch per unit effort in the coastal small-scale fishery of snapper Lutjanus synagris, of the Colombian Caribbean and their relationship with environmental variables

The coastal small-scale fishery in the Colombian Caribbean is characterized by the joint exploitation of demersal and pelagic species, which are caught using a variety of fishing gears. The snapper Lutjanus synagris, is one of the commercially important demersal fish species which is distributed throughout the Caribbean coast. We studied the spatio-temporal changes in the catch per unit effort (CPUE) of snapper, using data coming from the logbooks of the small-scale longline fishery. These data were obtained from hauls carried out in the Magdalena Department (73 degrees 34'W-75 degrees 0'W) between 1994 and 2001. The CPUE was standardized using Generalized Linear Models (GLM) considering year, month and zone of landings as factors. We also studied the relationship between CPUE with sea surface temperature (SST) and the runoff of the Magdalena River. The results showed important interannual changes in the CPUE. Although changes in CPUE are usually associated with changes in abundance, the standardized CPUE could obey mostly to changes in fishing power. Coefficients associated with the monthly factor showed the higher values CPUE during the rainy season (August-December) and between December-March, related with migrations of the demersal snapper ("bajanza"). No significant relationship between the SST and the CPUE was found. However, a significant and positive relationship was found between the CPUE and the discharge of the Magdalena River with a lag between one to three months. This relationship could be associated with an increment in the productivity due to the input of nutrients through of the river discharge. This process may affect positively the prey availability for snapper.