Distribución de la ictiofauna en un embalse con estratificación estival

Abstract

Studies were conducted to determine the spatial and vertical distribution of fish in a reservoir with summer stratification. Samples consisted of 24 h. capture with surface and bottom, trammel nets, over 18 stations and simultaneus echosoundings over 37 statiohs. The sarnpling was carried out rnonthl~d uring 1980 over the entire surface of the reservoir. For the calculation of the relative fish abundance the catch per unit effort (c.p.u.e.) is applied to the net results, and specific formulas to echo data. The results show a strong seasonal distribution pattern of the fish community. In spring and summer fish prevails in shallow zones with dense shore vegetation while in autumn and winter it shows an uniform distribution over all the reservoir. The vertical distribution is enfluenced by the limnologiccycle, with absence of fish in the hypolimnionduring the surnrner stratification due to oxygen scarcity.