Effect Of Tilapia Oreochromis Niloticus Over The Fisheries In El Guájaro Reservoir Atlántico - Colombia

Abstract

Objective: To evaluate the effect of tilapia, Oreochromis niloticus, over the fisheries in the El Guájaro reservoir, located in the Atlantico state, north of Colombia. Materials and methods: The reservoir has approximately 14.000 ha, and support the daily effort of 2.500 fisherman, coming from the eight Municipalities around. Through landing samplings carried out during 48 hours and a monthly frequency in all the ports, the abundance and composition of the captures were evaluated during 2002 and compared with the production during 1988 in the same ecosystem. Results: 38 fish species, belonging to 14 families, were identified. It was found that the production in 2002 was 431 ton/month, against 84 ton/month in 19During 2002, the composition of the captures was dominated by Oreochromis niloticus (53%) and Triportheus magdalenae (36%) this means a variation in the composition of the captures that during 1988 were respectively of 13% and 73%. This data however, did not affect the proportion of herbivores - carnivorous that stayed constant in 90-10 percent in the two periods of study. Conclusions: The changes in composition and abundance of the whole production suggest a displacement of a native species (Triportheus magdalenae) by an exotic (Oreochromis niloticus), which is being observed throughout the Magdalena river basin in this decade. © 2010 Universidad de Córdoba.