Curvina <em>Plagioscion squamosissimus</em> (Heckel, 1840) (Peciformes, Sciaenidae) feeding activity in Parana river

Abstract

Curvina Plagioscion squamosissimus (Heckel, 1840) feeding activity at the upper Paraná river floodplain (Porto Rico region, state of Paraná, Brazil) and Itaipu reservoir was investigated. The fishes were collected monthly with different mesh-sized gill nets October, 1986 through September, 1989 at upper Paraná river and November, 1983 through February, 1989 at Itaipu reservoir. The nets were set for 24 hours and the fishes were collected at sunrise (7A.M.), afternoon (3P.M.) and night (11P.M.) at Itaipu reservoir and each, three hours at upper Paraná river floodplain to determine daily feeding rhythm. Stomach repletion degree and food update frequency were used as stomach repletion indices. In both environments a high incidence of empty stomachs was registered. The annual variations of these indices were more pronounced in Itaipu reservoir. In terms of seasonal variations, feeding activities showed a higher frequency in hot seasons. Daily food intake showed to be more intense at early morning hours revealing that this species is a diurnal predator that uses visual stimulus to detect and pursue its preys.