Factors and constraints of the commercial fishing activity in the Central Amazon: a case study of a floodplain lake (The "Lago do Rei", Amazon, Brazil)

Following the observation that the commercial landings of fish on Manaus market are predominantly produced by the floodplain fisheries, a detailed case study was conducted in a floodplain lake near Manaus. The general characteristics of the fisheries exhibit a high level of complexity which can be reduced by considering two types of fisheries: a migration fishery and a lacustrine one. A study of the seasonal variability shows complex relationships between capture, effort and cpue, and the hydrological regime. The interannual evolution of these fisheries from 1976 to 1988 is analyzed. The total annual landings are maximum in the years 1979 and 1980, then decrease until the 1983/84 fishing season and seem to stabilize at a relatively low level in the last years. The main factor for these variations seems to be natural fluctuations in the fish populations

Ecological conditions of the production in a floodplain island of Central Amazonia: A multidisciplinary project

In the central sedimentary depression of the Amazon basin, two types of ecological settings are generally recognized: the "terra firme", the part never reached by the flood of the rivers and the floodplains locally called "várzea". Attempts at intensive exploitation of the "terra firme" in the 70's were very disappointing especially because of the soil poverty. As a consequence, in the 80's, the "várzea", was increasingly considered as an option for regional development. Floodplains are very productive environments which have been exploited from very early in the history of man. They are also very complex systems which are relatively poorly understood despite a large amount of research. In that context an international team conducted the interdisciplinary project "Ecological conditions of the production in a floodplain island of central Amazonia". This short term project consisted in 1) a description of the main system compartments (physical and climatic environment, water quality, soils, terrestrial and aquatic vegetation, soil invertebrates, fishes and shrimps) and 2) an analysis of the resources exploitation by human populations also taking into account historical factors

Fish communities of the "Lago do Rei", a floodplain lake in the Central Amazon: a general description

In an attempt to understand better the ecological basis of the high production generally observed in the floodplains, a detailed and global study was conducted on the fish community of a floodplain lake in the Amazon plain near Manaus. Community parameters were followed on a bimonthly basis, during a 27 month period (February 1986 - May 1988). The community is characterized by high values of specific richness and diversity and by a remarkable regularity in the distribution of the specific abundances. These parameters, and also the density and biomass of fish, vary on a seasonal and an interannual basis in relation with the hydrology of the system. In addition, the community is distributed among the different habitats in a heterogeneous way. Factorial analysis of correspondences show that the main source of variability is interannual and concern mainly the most marginal habitats. The seasonal variability has been related to the water level in the system. The results suggest that, in spite of this variability, the community is persistent and stable