Study on the Length–Weight Relationship, Condition Factor, and Relative Weight of Six Fishes in the Lower Yarlung Zangbo River, Southwest China

The lower reaches of Yarlung Zangbo River are one of the most important biodiversity hotspots worldwide. Fishes in the area are of great research value, ecological and fishery value, but little biological information about these fishes is available, restricting the conservation and development of local fish resources. This study aimed to provide basic biological data for these fish by studying the length–weight relationships (LWRs) of six indigenous fish species from the lower Yarlung Zangbo River catchment, Tibet, China. Totally, 1262 specimens belonging to four families, six genera, and six species were collected from 2022 to 2024 using various types of fishing techniques. The LWRs of Garra yajiangensis, Nemacheilus subfusca, Creteuchiloglanis kamengensis, and Exostoma tenuicaudatum were reported for the first time to FishBase, except Neolissochilus hexagonolepis and Psilorhynchus homaloptera. The maximum standard-length information of G. yajiangensis, P. homaloptera, N. subfusca, and E. tenuicaudatum was updated to FishBase. The a and b values calculated from the LWRs ranged between 0.007 and 0.020 and 2.760 and 3.292, respectively. Interspecific and intraspecific variations in LWRs were observed in these fishes. Growth patterns of N. hexagonolepis and C. kamengensis were isometric, while those of other fishes were strongly allometric. Condition factors of species varied between 1.09 and 1.99, and the relative weight ranged from 99.87 to 104.18. Within species, there were significant temporal and spatial variations of LWRs, condition factor, and relative weight for these fishes, respectively. The findings of this study are essential for the conservation and management of local fish and fisheries.