Effect of water quality on growth of four fish species in the Iténez basin (Upper Madera, Amazon)

Abstract

Fish growth is an indicator of populations’ life conditions that could be used to detect stress due to contamination. In this study, age of fishes of four species (Psectrogaster essequibensis, Schizodon fasciatus, Triportheus angulatus and Pygocentrus nattereri) from the Itenez basin (Upper Madera, Amazon) were estimated by otolith readings, and growth parameters were estimated by using the Von Bertalanffy Growth Function. Populations of four sites were compared in order to detect the effect of natural and anthropogenical water chemistry differences. One of these sites was directly impacted by gold mining activities whereas the three others were only influenced by mild human activities and presented white or clear waters. Species growth coefficient (K) varied from 0.28 (P. nattereri), to 0.39 (P. essequibensis), 0.69 (S. fasciatus) and 1.71 (T. angulatus). Due to the limited size samples, these values have to be considered as preliminary regional approximation. For S. fasciatus, P. nattereri and T. angulatus, residuals analysis of the growth function showed differences among the three unimpacted sites. However, each species exhibited different patterns of growth variations among sites, thus preventing to clearly demonstrate a general effect of water chemistry on the fish growth of these populations. On the contrary, for these three species fish growth appeared weaker in the gold-mining site.