Length-to-weight and length-to-length relations were estimated for 15 freshwater fishes belonging to the order Cypriniformes from Yuxi power station to Kaitan reservoir dam trunk stream of the Oujiang River, Zhejiang Province, China. The following species were studied: Distoechodon tumirostris Peters, 1881, Xenocypris davidi Bleeker, 1871, Plagiognathops microlepis (Bleeker, 1871), Hemibarbus labeo (Pallas, 1776), Hemibarbus maculatus Bleeker, 1871, Chanodichthys erythropterus (Basilewsky, 1855), Culter alburnus Basilewsky, 1855, Chanodichthys dabryi (Bleeker, 1871), Opsariichthys bidens Günther, 1873, Zacco platypus (Temminck et Schlegel, 1846), Sinibrama macrops (Günther, 1868), Hemiculter leucisculus (Basilewsky, 1855), Pseudohemiculter hainanensis (Boulenger, 1900), Rhodeus sinensis Günther, 1868, and Squalidus argentatus (Sauvage et Dabry de Thiersant, 1874). The determination coefficients r2 of LWRs were all over 0.96, and the 15 values of parameter b were consistent with the predicted range of 2.5–3.5. The total length-to-standard length relations were also calculated with r2 ≥ 0.97. Our study provides new information on LWR for 1 species and LLRs for 8 species, as well as new maximum total length recorded for 4 species (i.e., Distoechodon tumirostris, Opsariichthys bidens, Pseudohemiculter hainanensis, and Rhodeus sinensis) in FishBase. This study is expected to provide a useful baseline for further studies of population parameters to improve management decisions on the Oujiang River.

Population dynamics parameters and stock status of Squaliobarbus curriculus (Richardson, 1846) were analyzed from May to September 2021 in the Lanxi section of Qiantang River. FiSAT II software program was used. The growth coefficient K = 0.21 year -1 , asymptomatic length L ∞ = 39.48 cm, and age at theoretical zero-length t 0 = -0.74 years were estimated. The von Bertalanffy growth function was calculated as L t = 39.48[1 -e -0.21(t + 0.74) ]. The growth curve for weight had an inflection at 5.86 years, corresponding to 29.61 cm in standard length and 372.29 g in weight. The natural mortality rate (M), the fishing mortality rate (F), and the total mortality rate (Z) were calculated as 0.51, 0.61, and 1.12 year -1 , respectively. The exploitation ratio (E) was 0.54, which is greater than the value of 0.5 suggested by Gull (1971), indicating a probable state of overdevelopment. The annual average stock number and biomass of S. curriculus in the Lanxi section of Qiantang River were 31.86 × 10 6 individuals and 3656.82 t, respectively.

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.