Length-weight and length-length relationships for freshwater fish species from the lower Araguaia River, Tocantins-Araguaia basin, Tocantins State, Brazil

Abstract Length-weight (LWR) and length-length (LLR) relationships were estimated for 51 freshwater fish species caught in the lower Araguaia River, Tocantins-Araguaia basin, Tocantins State, Brazil. Sampling was conducted from March to September 2009 at seven sites along the main river channel. Significant differences in LWR between sexes were found in nine fish species. Isometric growth (b = 3) was observed in 21 fish species. The average b-value was 2.95 (SE = ± 0.05). The average b-value for LLR was 1.158 (SE = ± 0.018). Significant differences in LLR between sexes were found in seven fish species. In four species, females were larger than males of the same species. This study provides the first references for LWR and LLR in nine and 12 fish species, respectively, as well as new maximum total lengths for 15 species. These parameter estimates can be used to assess species conservation status and to develop models of fish growth, reproduction, and fisheries management.