Variação nas estruturas ecomorfológicas e trófica da espécie de peixe poecilia reticulata entre riachos sob diferentes pressões ambientais na região de Londrina-PR

Abstract

The present study had as objective to evaluate how different environmental impacts affect the trophic structure of individuals of the fish species Poecilia reticulata in two streams of the region of Londrina-PR, correlating with the intraspecific alterations in the ecomorphology, to verify if such structure can be used as indicator of environmental quality. For this purpose, individuals were collected in the years 2013 and 2014 in the Cambé (urban) and Taquara (rural) streams. The fish were collected by manual and electric fishing, with a sampling effort of 40 minutes each, fixed in 10% formaldehyde and preserved in 70% alcohol. The collections were done quarterly to cover the four seasons of the year, in three sampling points in each stream, totaling six sampling points. In the laboratory, after being identified, 10 individuals of each sex per point and collection were selected, since the species presents sexual dimorphism. In order to ascertain the ecomorphological patterns, 26 ecomorphological indexes were calculated, later, summarized by the principal component analysis (PCA), in order to evaluate if the differences between the points were significant, statistical analysis was performed using ANOVA. For the analysis of the trophic structure, the individuals were gutted and had the first third of the stomach analyzed, for each item the frequency of occurrence (FO), number frequency (FN) and volumetric frequency (FV) were calculated, and with them the Relative Importance Index (IIR) was calculated. In order to verify variations in the food habit of the species under study, the Detrended Correspondence Analysis (DCA) was applied on the indices of relative importance (IIR). To evaluate the existence of significant differences in feeding patterns, the non-parametric multivariate similarity analysis (ANOSIM one-way) was applied. The limnological parameters were measured locally, they were: dissolved oxygen, pH, electrical conductivity and turbidity. The differences between the points were tested by a Multivariate Analysis of Variance (MANOVA). To verify the degree of urbanization of the basins, the percentages of waterproofing of each basin were used. A total of 222 individuals, 107 females and 105 males were analyzed. In the light of the objectives the results were significant, PCA completely discriminated the sexes, however, only males of point 3 Cambé and point 1 Taquara were significantly different (p = 0.02). There was a preference for autochthonous resources in all points, however, there was a great dissimilarity among them (R = 0.79 and p = 0.02), with insect larvae for Cambé and algae in Taquara. Regarding the physical-chemical parameters, all are within the values allowed by CONAMA 357, however, an increase in OD, pH and turbidity was observed for Taquara in relation to Cambé, as well as a decrease in electrical conductivity, differences demonstrated by MANOVA (p = 0.001). Cambé also presented a high degree of waterproofing. The results indicated that there were differences between the individuals of Poecilia, as well as between the points of the two microbasins studied, emphasizing that the anthropic impacts, mainly the urbanization, exert influence on the structure of the communities.