Fishery production and biological productivity in public reservoirs of Northeast Brazil

Abstract

Based on data for period 1948/1988, sorting out the reservoirs according to the river systems where they have been built, information was obtained on fishery and natural indices of productivity, features of the reservoirs as to age, area of catchment basin, water volume and mean depth, as well the ideal combination of herbivorous and carnivorous species by means of an F/C Relationship in weight. The main results are: (1) the public reservoirs are distributed in 25 river systems, among which stand out Jaguaribe, Piranhas, Acaraú and Itapicuru; (2) the most productive reservoirs are Orós, Arrojado Lisboa, Estevam Marinho, Engenheiro Ávidos, Paulo Sarasate and Jacurici; (3) the mean fishing yield is 105.0 kg/ha.year, corresponding to a natural productivity of 35.7 kg/ha.year, as determined by the biomass of indigenous species; (4) the F/C Relationship has varied along the years, but since 1977 has levelled off around 1, what means the possibility of the maximum sustainable yield of the community having been attained from a given quantity of fingerlings for restocking; (5) the Morphoedaphic Index mean value is 3.867 ppm/meter, reaching its peak value in the river systems of Pernambuco/Alagoas area (9.157 ppm/meter) and its lowest in the area of Piaui, with 0.962 ppm/meter; (6) the public reservoirs of northeastern Brazil are supposed to have attained an old age, meaning that its productivity has a definite decreasing trend that can only be reverted by intensive and balanced restocking programs.