Salmito-Vanderley, Carminda Sandra Brito creator Ferreira, Pedro Emidio Leite Moraes creator Souza, Mirley Barbosa de creator Madeira, Guilherme Melo creator Brito, Bruna Faria creator Magalhães, Lívia Correia creator Melo, Carlos Henrique Sousa de creator Montenegro, Assis Rubens creator text periodical abstract or summary bl. continuing eng ABSTRACT - The Brazilian bocachico is a rheophilic fi sh from the northeast region of Brazil that holds great economic and scientific interest. The absence of evident sexual dimorphism and the invasive character of sexing methods and evaluation of gonadal maturation are obstacles to its artifi cial reproduction. In this scenario, ultrasonography emerges as a non-invasive method for sexing. The objectives of this study were to establish an ultrasound sexing method for Brazilian bocachico and select equations to estimate the gonadosomatic index (GSI), gonad weight (GW), and gonad volume (GV) of live bocachico. A total of 32 bocachico fi sh (18 females and 14 males) were analyzed ultrasonographically and morphologically. The association of morphometric and ultrasonographic parameters was investigated using Pearson Correlations. The following prediction equations were selected using multiple regression analysis: GSI = 16.22 × transvarea; GW = 30.3 × transvarea; and GV = 0.001260036 × pixels. A model capable of predicting the sex of the animals based on the ultrasonographic parameters was obtained using partial least-squares discriminant analysis with principal component analysis. The significance level adopted was P < 0.05. In conclusion, ultrasonography is a useful tool to perform sexing and evaluate the gonads during the breeding season, contributing to artificial reproduction in captivity. Key words: Fisheries. Brazilian Bocachico. Native fi sh. Gonadosomatic Index. Ultrasound. Publicação on-line; 22 ref.; 6 illus.; Summary (En) PEIXE DE ÁGUA DOCE REPRODUÇÃO ANIMAL ULTRASSOM Fortaleza-CE Universidade Federal do Ceará. Centro de Ciências Agrárias 2002 2023-437436 0045-6888; 1806-6690 (on-line) BR2023002374 v. 54 p. 1-8; (2023) https://www.scielo.br/j/rca/a/59sfzr7vQfprppn4KVjqBwQ/?format=pdf&lang=en https://www.scielo.br/j/rca/a/59sfzr7vQfprppn4KVjqBwQ/?format=pdf&lang=en BR-BrBNA 240209 20240209133358.0 eng