Length‒Weight and Length‒Length Relationships of Freshwater Fish Species Caught by Professional Fishermen in the Itaipu Reservoir, Brazil

Abstract

Length‒weight relationships (LWRs) and length‒length relationships (LLRs) were estimated for 63 and 58 freshwater fish species, respectively, captured in the Itaipu Reservoir, Paraná River Basin, Paraná State, Brazil. Sampling was carried out from March 1987 to July 2024 at 63 professional fishing sites within the reservoir’s area of influence. Statistically clear differences in LWR between sexes were detected in 26 species. Isometric growth (b = 3) was identified in 29 species. The b-value ranged from 1.14 to 3.89, with an average of 2.68 (SE ± 0.04) across all species. For LLR, the b-value ranged from 0.713 to 1.440, with an average of 1.12 (SE ± 0.01) across all species, with statistically clear differences between sexes observed in 19 species. In 16 species, females were larger than males. This study provides the first LWR references for 13 species and LLR references for 22 species, as well as new maximum total length records for 39 species and maximum total weight records for 41 species. These estimates are crucial for managing fish stocks and developing models related to fish growth, reproduction, and fisheries.