Discrimination of species and populations of the genus Cichla (Cichliformes: Cichlidae) in rivers of the Amazon basin using otolithic morphometry

Abstract

The genus Cichla is a highly diverse group, with 16 species already described. Externally, some species are very similar and discriminating between them may be very difficult. Nevertheless, discrimination of fish stocks is essential for management purposes. Morphometric analyses of otoliths have been successfully used to distinguish species and fish stocks, especially in marine environments. This study evaluated whether sagittal otolith shape can be used to discriminate among the species Cichla temensis, C. monoculus, and C. orinocensis, as well as within populations of C. temensis in rivers of the Amazon. Shape indices and Fourier coefficients were used to describe the shape of the otoliths. Among the groups of species, the morphology of the sagittal otolith of C. temensis was totally distinct from the species C. monoculus and C. orinocensis. While among populations of C. temensis, individuals from the Negro and Jatapú Rivers were different, regardless of the methods used. These results confirm the ability to differentiate species and populations by using the morphology of otoliths. However, more research is needed to verify the role of genetic versus environmental and biotic effects, and thus be able to explain the discrimination observed in otoliths.

A new species of Astronotus (Teleostei, Cichlidae) from the Orinoco River and Gulf of Paria basins, northern South America

“…The analysis of the morphology of the sagitta otolith supports the distinctive taxonomic status of several fish species (Mereles et al 2021, Reichenbacher et al 2007. However, the morphology of the sagitta otoliths was never used in previous studies for Astronotus species.…”

Isotopic niche alteration of a predator fish in a dammed Amazonian black water river

“…Individuals were therefore collected exclusively downstream of the Balbina Dam in the Uatumã River and the Jatapú River; both sampling sites are 25 km from confluence between Uatumã and Jatapú rivers. Studies based on otolithic morphometry found differences in the shape of the otoliths of C. temensis from Uatumã and Jatapú individuals, suggesting that the populations of each river are distinct (Mereles et al, 2021). Specimens of C. temensis were caught with fishing rod and artificial bait.…”