Fish were captured using trammel nets in the pelagic habitats and trap nets in the shallow habitats (Melcon 1964, Granado-Lorencio 1996). Trap nets were used in habitats such as shallow coves, shoreline areas, banks and the tail end of the reservoir. The trap nets (or dutch trap nets) used in the study were 6 m long and had a single mesh of
15 mm. They are formed by a guide and four traps connected consecutively, each one of them of smaller entrance diameter to the previous one. They were set up in areas with development of vegetation, either macrophytes or other vegetative formations (i.e. roots or flooded old trees). Trammel nets (12 x 2 m) were set up in open water (depth over 2 m). These had a narrow inner mesh of 25 mm and an outer mesh of 100 mm. In areas deeper than 8 m, two nets were set up, one at the surface and one at the bottom. In areas shallower than 8 m, only one net was set up at mid depth. In all cases, nets were fishing during 24 hours, being examined twice during the period of exposition