| Catch per unit effort (CPUE), lenght distribution, age, growth, reproduction, migrations and feeding were studies through samples collected with longlines and a gang of gill-nets of several mesh size. CPUE data showed a progressive decrease of the relative abundance in the Río de la Plata, during the study period. Age was studied from scales. Back-calculations of growth revealed the pressence of Lee's phenomenon. Means lenghts at age were greater in females. No significant difference was found in lenght-weight regressions from both sexes and sampling areas. Only young individuals from 1 to 6 years were caught. None of the fish studied had ripening gonads. Extensive migrations were recorded both in the Paraná and Uruguay rivers. Stomach contents analysis... |
