O fitness em uma perspectiva ecológica: Estudo de caso com peixes estuarinos-dependentes em um sistema estuarino urbano

Abstract

Fitness is an important evolutionary property present in every living organism. Climate change and human actions in coastal ecosystems have shown a series of effects on the fitness of marine fish assemblages around the planet. Based on this premise, evaluating the fitness responses of fish assemblages becomes an important tool to understand the life history of natural populations and the conservation status of coastal ecosystems of high economic and ecological value, such as estuaries. In this work were evaluated the reproductive and growth components, as well as the feeding of four species of estuarine fish of the estuary of Paraíba do Norte River, Paraíba, Brazil. The hypothesis tested in this work was that in more polluted areas the growth and fecundity of fish changed when compared to less polluted areas. The samplings were carried out during the year 2019, during the rainy and dry period of the region, where the environmental variables and the concentration of organic pollutants in the water body of the estuary were measured and sampled the taxocenosis of fish. To measure the fitness components of the studied species, were used Fulton's K factor, the Gonadosomatic Index (GSI) and the oocyte count in females. The influence of these variables on fitness was evaluated using the GLMM. For the diet analysis were used volumetric frequency (FV%), food vacuity index (VI), for the niche breadth was used the Shannon index and SIMPER was used to test the contribution of prey dissimilarity. As main results, was observed that the nutrients PO43- and NO2- have negative effects in most of the studied fish species. The GSI was the fitness metric that suffered the most reduction in its values due to the higher concentrations of PO43- and NO2-. The K factor and oocyte count differed between zones and seasons with the influence of organic pollutants only in some species. The GLMM showed that organic pollutants had a greater influence on the quality of the offspring, with a reduction in the GSI, than on the quantity, since the productivity of oocytes by the females showed a certain constancy. Regarding diet, the zooplankton, benthic macro invertebrates and insects were the main items consumed by fish species. The insects proved to be an important food resource in the most polluted areas, being the main responsible for the dissimilarity observed. The results evidenced the influence of pollutants, mainly nitrite, on the life history of wild fish populations. The nitrite had an effect for all species, with the exception of R. bahiensis. The present work emphasizes the influence of nitrite on the fitness of different fish populations, in addition to reinforcing the importance of allochthonous resources in estuaries impacted by anthropic action, however, more studies are still needed to better explain the effects of anthropic actions on the life history and fitness of wild fish populations.