Análises morfométricas em otólitos de espécies do gênero Cichla em rios da bacia Amazônica

Abstract

In order to increase the framework of techniques that make it possible to advance the knowledge of the population parameters of fish species, the present study used two morphometric approaches employing traditional techniques (linear measurements) and geometric, on Cichla species, with the objective of establishing morphometric relationships between the body and the otolith, and distinguishing species and populations through the shape of the sagitta otolith. For this, the sagittae otoliths of the species Cichla temensis, C. orinocensis and C. monoculus were sampled, collected in three rivers (Negro river, Uatumã river and Jatapú river) belonging to the Amazon basin. Using linear measurements, relationships were established between the body and the otolith of the species Cichla temensis. The linear regression models for the weight and length of the otoliths in relation to the same body dimensions of the fish showed strong correlations, mainly for the variable weight with an r2 = 0.92, while the length had an r2 = 0.77. Thus indicating that the dimensions of the otoliths can be used to estimate the size of the individuals of the species studied, and can also be adapted for other fish species. When assessing the shape of the sagittae otoliths to discriminate Cichla species and populations, differences were found between both groups. Among the group of species, the shape of the C. temensis sagitta otolith proved to be completely different from the species C. monoculus and C. orinocensis. While in the group of C. temensis populations, individuals from the Negro and Jatapú rivers are different regardless of the methods used to describe the shape of the otoliths. The differences found in the shape of the otolith in the group of species can be directly related to genetic factors, while the morphology of the otoliths of the populations can be influenced by environmental variations. These results confirm the ability to differentiate species and populations through the morphology of the otoliths, however, further studies are needed to verify the role of the genetic effect in comparison to the environmental and biotic effects to clarify the differences observed in the otoliths.