Morphological differentiation among migratory fish species from the Paraná River basin

This study characterized the morphological differences among migratory fish species from the Paraná River Basin. A total of 177 adult fish of Leporinus elongatus, Leporinus macrocephalus, Prochilodus lineatus, Salminus brasiliensis, Pimelodus maculatus, Pinirampus pirinampu, Pseudoplatystoma corruscans, Pterodoras granulosus, and Rhaphiodon vulpinus were sampled in the Canal da Piracema, a fish passage system at Itaipu Dam, Paraná River. The migratory species were analyzed through 22 morphometric measurements and fineness ratio to identify morphological patterns related to swimming performance. Four species groups were indicated by the Cluster analysis: I) R. vulpinus; II) P. corruscans; III) L. macrocephalus, L. elongatus, P. lineatus, P. maculatus, and S. brasiliensis - measurements of head height and anal fin length formed this group; and IV) P. granulosus and P. pirinampu - measurements of maximum body width and caudal peduncle width contributed to form this group. The morphometric variables that most contributed to the distinction were head length and mouth width for groups I and II. The species R. vulpinus and P. granulosus differed from other species, showing fineness ratios of 9.4 and 3.7, respectively. Leporinus elongatus, L. macrocephalus, P. lineatus, P. maculatus, and S. brasiliensis showed significant differences from other species, with ratios ranging from 4.57 to 5.19, indicating that these species may be better swimmers. Long-distance migratory species using the Piracema Canal to ascend upstream areas differed morphologically, morphological characteristics such as a narrow caudal peduncle and maximum body length, besides to the values of the fineness ratio, were essential to differentiate the migratory species. Este estudo caracterizou as diferenças morfológicas entre espécies de peixes migradores da bacia do rio Paraná. Um total de 117 peixes adultos das espécies Leporinus elongatus, Leporinus macrocephalus, Prochilodus lineatus, Salminus brasiliensis, Pimelodus maculatus, Pinirampus pirinampu, Pseudoplatystoma corruscans, Pterodoras granulosus e Rhaphiodon vulpinus foram capturados no Canal da Piracema, um sistema de transposição para peixes na barragem de Itaipu, rio Paraná. As espécies migradoras foram analisadas através de 22 medidas morfométricas e razão fineza para identificar padrões morfológicos relacionados à capacidade natatória. Quatro grupos de espécies foram evidenciados pela Análise de Cluster: I) R. vulpinus; II) P. corrusca