POPULATION-STRUCTURE AND REPRODUCTIVE-BIOLOGY OF LORICARIICHTHYS PLATYMETOPON (SILURIFORMES, PISCES) IN THE UPPER RIVER PARANA

Distribution, length, and reproductive biology of Loricariichthys plat ymetopon were analyzed in different environment of the upper Parana Ri ver. Samples were taken monthly from October 1986 to September 1988 us ing gillnets with different mesh size, being caught 7691 individuals. This species was more constant and showed higher densities in lentic e nvironment than in other ones. Reproductive activity was more intensiv e in lentic environment, and under condition of low transparency and l ow concentration of dissolved oxygen. Spawning was observed from Septe mber 1986 to January 1987 when flood was absent and from September 198 7 to April 1988 under normal flood conditions. Transportation of the e ggs (340 on average) under the lips by males is a strategy appropriate for varying water levels and the limnological factors of floodplain l agoons, the main spawning environment.