Summary Length–weight relationships were determined for seven fish species (Culter oxycephaloides Kreyenberg & Pappenheim, 1908; Pseudobagrus tenuis Günther, 1873; Saurogobio dumerili Bleeker, 1871; Distoechodon tumirostris Peters, 1881; Pseudolaubuca engraulis Nichols, 1925; Liobagrus marginatoides Wu, 1930; and Parabotia bimaculata Chen, 1980) inhabiting the Yuan River, central China. Fishes were collected using gillnets and electroshock fishing techniques quarterly from January 2008 to December 2010. This study is first report the length–weight relationships for this seven fish species.

The length–weight (LWRs) and length–length (LLRs) relations were estimated for 16 fish species obtained from Jiaxing section of the Beijing–Hangzhou Grand Canal, China. One species represented Engraulidae: Coilia nasus Temminck et Schlegel, 1846; 11 species Cyprinidae: Hypophthalmichthys molitrix (Valenciennes, 1844); Hypophthalmichthys nobilis (Richardson, 1845); Chanodichthys erythropterus (Basilewsky, 1855); Chanodichthys mongolicus (Basilewsky, 1855); Culter alburnus Basilewsky, 1855; Chanodichthys dabryi (Bleeker, 1871); Pseudobrama simoni (Bleeker, 1864); Hemiculter leucisculus (Basilewsky, 1855); Megalobrama terminalis (Richardson, 1846); Carassius auratus (Linnaeus, 1758); Cyprinus carpio Linnaeus, 1758; one species Bagridae: Tachysurus fulvidraco (Richardson, 1846); two species Odontobutidae: Odontobutis potamophilus (Günther, 1861); Micropercops swinhonis (Günther, 1873); and one species Osphronemidae: Macropodus ocellatus Cantor, 1842. Fishes were collected using multipanel nylon gillnets with mesh sizes of 1–8 cm from November 2020 through August 2021. All fishes were measured for length (total length, TL; standard length, SL) to the nearest 0.1 cm and weight (W) to the nearest 0.1 g. The coefficients of determination R2 of LWRs and LLRs were all over 0.950, and the 16 values of LWR parameter b were estimated from 2.505 to 3.364. Our study provides new information on LWRs for 2 species and LLRs for 7 species, as well as a new maximum total length recorded for 3 species for FishBase. This study would allow for the convenience of the conversion of TL–W and SL–TL in fish stock assessment and is expected to provide a useful baseline for further studies of population parameters to improve management decisions.