Length Weight Relationships of Commercial Fishes from the Mainstream of Yellow River, China

The fish specimens were collected from July to November in 2018 from 34 sampling points on the mainstream of Yellow River (33°47′-37°23′N, 99°41′-118°12′E). The specimens were collected by gill nets (mesh size: 3-5 cm, length: 80-100 m, height:1.5-2 m), fish cages (mesh size: 0.5 cm, length: 2-3 m) through everyday independent sampling (fishing nets were put in river water body at dusk about 16:00-18:00 o’clock and collected in the following early morning about 7:00-9:00o’clock) and electrofishing technique (CWB-2000 P, 12V, 250 Hz). All fish specimens were identified immediately to the species level according to Li (2017) and rechecked based on FishBase (Froese and Pauly, 2018). Standard length (SL, nearest to 0.1 mm) and body weight (W, nearest to 0.1 g) were measured for each sample. LWRs were estimated using the equation: W = aLb, where a and b are the equation parameters calculated by the least squares method using the logarithmic form of the equation: Log W= Log a + b Log L, where W is the body weight (g), L is the standard length (cm). The log-log plots of length and weight data were performed for visual inspection of outliers and obvious outliers were removed according to the plot of the log W over log L (Froese, 2006). The statistical significance level of the coefficient of determination (r2) and 95% confidence intervals (95%CI) of a and b were also estimated.

In the present study, the LWRs of 1168 individuals from 18 species representing 4 families and 17 genera were determined. The following species were covered: Leuciscus chuanchicus (Kessler, 1876); Ctenopharyngodon idella (Valenciennes, 1844); Squaliobarbus curriculus (Richardson, 1846); Parabramis pekinensis (Basilewsky, 1855); Hemiculter leucisculus (Basilewsky, 1855); Culter alburnus (Basilewsky, 1855); Rhinogobio nasutus

Table I. Descriptive statistics and estimated parameters of length-weight relationships for commercial fish species from the mainstream of the Yellow River, China.

n denote number of analysed specimens, SL denote standard length, W denote body weight, a coefficient of proportionality, b denote allometric coefficient, CI denote confidence limit, R2 denote coefficient of determination, + denote no data about LWRs in FishBase (Froese and Pauly, 2018).

(Kessler, 1876); Hemibarbus maculatus (Bleeker, 1871); Cyprinus carpio (Linnaeus, 1758); Carassius auratus (Linnaeus, 1758); Hypophthalmichthys molitrix (Valenciennes, 1844); Hypophthalmichthys nobil (Richardson, 1845); Gymnocypris eckloni (Herzenstein, 1891); Schizopygopsis pylzovi (Kessler, 1876); Triplophysa siluroides (Herzenstein, 1888); Silurus lanzhouensis (Chen, 1977); Silurus asotus (Linnaeus, 1758); Channa argus (Cantor, 1842). The most abundant species included Cyprinus carpio, Carassius auratus, and Silurus asotus. The values of coefficient a ranged from 0.0066 (Culter alburnus) to 0.0824 (Ctenopharyngodon idella), and the values of exponent b ranged from 2.598 (Ctenopharyngodon idella) to 3.271 (Parabramis pekinensis). The coefficient of determination values (r2) in the majority of LWRs were high (r2 > 0.934). Moreover, the LWRs for five species were determined for the first time (denoted in Table I). Leuciscus chuanchicus, Rhinogobio nasutus, Schizopygopsis pylzovi, Triplophysa siluroides, and Silurus lanzhouensis according to FishBase (Froese and Pauly, 2018).

In the present study, all the estimated b values remained within the excepted range of 2.5-3.5 (Froese 2006). Multitude of factors, such as number of specimens, fish habitat, degree of stomach fullness, sex, stage of gonadal maturity, and length range of the specimens, are known to cause variation in b value of fishes (Froese 2006; Borah et al., 2018). The present study reports the b value of Schizopygopsis pylzovi as 2.912, which was different from congeneric species Schizopygopsis malacanthus derived from the upper Jinsha River (b as 3.060) (Lin et al., 2015). The reason may be attributed to (a) different fish habitat environment scenarios and (b) to different length range of the specimens compared to our method, and individual biological differentiation. In conclusion, it is the first time to study the LWRs for the species in the whole mainstream of the Yellow River. The results will be meaningful for further research about sustainable development and scientific management of fishery resources of the Yellow River.

This research was supported by National Natural Science Foundation of China (No.51709225), Shaanxi Natural Science Foundation (No.2018JQ5121) and Startup Foundation for Doctor of Xi’an University of Technology (No.104-451118020).

The authors have declared no conflict of interest.