Length-weight and length-length relationships, and length at first maturity of freshwater fish species in the Salto Osório Reservoir, Iguassu River Basin, Brazil

ABSTRACT Length-weight relationships (LWR) and length-length relationships (LLR), along with length at first maturity (L50), were estimated for 24, 25, and 16 freshwater fish species, respectively, caught in the Salto Osório Reservoir, Iguassu River Basin, Paraná State, Brazil. Sampling was conducted over a 20-year period at three sites within the reservoir’s influence area. Significant differences in LWR between sexes were observed in 15 fish species. Isometric growth (b = 3) was recorded in six species, with an average b-value of 2.87 (SE ± 0.06). The average b-value for LLR was 1.143 (SE ± 0.020), with significant differences between sexes found in 14 species. Length at first maturity was estimated for 16 species, with significant sex-based differences in L50 observed in two species. This study provides the first references for LWR, LLR, and L50 in nine, 12, and 10 species, respectively, as well as new maximum total lengths for 20 species. These parameter estimates can support assessments of species conservation status and inform models of fish growth, reproduction, and fisheries management.