First Records of Length–Weight Relationships for Ten Fish Species From the Middle Stretch of the Uruguay River, Southern Brazil

This study estimated the length–weight relationships (LWRs) of 10 fish species from the middle stretch of the Middle Uruguay River basin, aiming to provide new morphometric data and contribute to the knowledge of Neotropical ichthyofauna. Fish were collected at seven sites with sampling conducted at each site during every season, totaling 84 sampling campaigns between May 2016 and February 2019. Different fishing gears were used, including gillnets (15–80 mm), three‐panel nets (150.30.150; 150.40.150; 150.50.150 mm), a beach seine (8 mm), and longlines (100 m, 30 hooks, sizes 5/0 and 12/0) baited with small fish, maize, and snails. The parameters a and b of equation W = aL b were estimated for each species, revealing five species with positive allometry, two with isometry, and three with negative allometry. The b coefficient ranged from 2.456 in Pseudoplatystoma corruscans to 3.336 in Acestrorhynchus pantaneiro . These records expand the current database on the regional ichthyofauna and provide relevant information for conservation and fisheries management in the middle stretch of the Uruguay River basin.