Abundancia de peces en el caño Macareo, delta del Orinoco: una aproximación mediante técnicas de hidroacústica en fondos someros

The fisheries resources associated to the mouth of Macareo lowland stream (Orinoco delta) were evaluated by hydroacoustic techniques on shallow waters, using a scientific echosounder SIMRAD EY500 with elliptical transducer of 12.2 x 11,3° and 70 kHz. Two indicator parameters were used: fish density and sA total (acoustic density) to map the horizontal distribution and the vertical structure of the fish communities related to time. During the dry season (March 2005) when tide fluctuations generated noticeable salinity gradients (6 to 28), more than 700 fish/1000 m3 were observed down river and acoustic densities reached up to 3000 m2 /nm2 in the central section of the study area. During the rainy season (August 2006), with few hydrological variations and low salinity, the fish densities were lower; nevertheless, the spatial distribution of the biomass was similar. The results suggest that during the rainy season, fish of smaller size, many of them brackish water species, leave the estuary, while Siluridae species wich have a bigger size remain in the zone the whole year.