Length-Weight Relationships of 8 Plateau Indigenous Fishes of Xinjiang, China

Data were collected from eight sites using gill nets and ground-based bamboo cages from March 2016 to October 2019 (Table I). Five kinds of Schizothorax fishes (16 Schizothorax biddulphi, 42 Gymnodiptychus dybowskii, 27 Schizothorax irregularis, 35 Diptychus maculatus, and 35 Schizothorax pseudaksaiensis), two kinds of Triplophysa fishes (25 Triplophysa zamegacephala and 60 Triplophysa microphysa) and 34 Perca schrenkii were collected (Table II). Each sample’s standard length (SL) was measured to an accuracy of 0.01 cm, and the precision of body weight (BW) was 0.01 g. The relationships between length and weight are expressed as follows: W = a × Lb, where W is the weight (BW, g), L is the standard length (SL, cm), a is the intercept, and b is the allometric growth coefficient. Following Froese (2006), before the regression analysis of BW on SL, the ln-ln diagram of length and weight was used to inspect the abnormal values visually, and the extreme values were excluded from the regression analysis. The statistical significance level of r2 was estimated. All data analysis was carried out using SPSS 18.0 (SPSS Inc.) and Origin 8.0.

Analysis of 274 samples of eight kinds of fish was performed. Table II gives the sample size, size range (cm, TL, G, and BW), longitudinal relationships parameters a, b, and r2, and 95% confidence limits of a and b. The statistical relationships between the length and weight of all eight species were highly significant (p < 0.001), and the r2 value was > 0.819. The value of parameter b remained within the expected range of 2.762-3.320 (Froese, 2006). According to the LWRs predictions (Froese et al., 2014), the estimated values of the a and b parameters of the eight species of fish in this study were consistent with the prediction results and showed high significance for the body length-weight relationships (p<0.01). Length-weight relationships parameters may vary between seasons and are influenced by factors such as maturity, temperature, salinity, acquired food and food utilization (Sui et al., 2015; Asadi et al., 2017).

The b-value can be used to judge the growth state of fish. The b-values ranged from 2.762 (Triplophysa microphysa) to 3.320 (Diptychus maculatus), with b-values remaining within the expected range of 2.5-3.5 (Froese, 2006). T-tests of the b-values of eight species of

Table II. Descriptive statistics and estimated parameters of LWRs (W = a × Lb) for eight fish species from Northwest China.

n denotes the number of analyzed specimens, SL denotes the standard length, BW denotes the body weight, a is the coefficient of proportionality, b is the allometric coefficient, CI is the confidence limit, r2 is the coefficient of determination, and + denotes a lack of LWR data in FishBase.

fish with 3 (Pauly, 1984; Froese, 2006) indicated the b-values of Schizothorax biddulphi, Diptychus maculates, Schizothorax pseudaksaiensis, Triplophysa microphysa, and Triplophysa zamegacephala were significantly different from 3 (p < 0.05). Among them, the b-value of Triplophysa microphysa was < 3, which indicates a negative allometric growth pattern. The b-values of Schizothorax biddulphi, Diptychus maculates, Schizothorax pseudaksaiensis, and Triplophysa zamegacephala were > 3, which indicates a positive allometric growth pattern. Notably, the b-value differed within Triplophysa microsa (Bhat et al., 2010). The sampling location and number of samples in this study were similar to those in the study of Triplophysa microphysa by Bhat et al. (2010) but the sampling time was different. Therefore, it can be speculated that the difference in b-values may be due to the different sampling times leading to different sexual maturities of the samples. Studies have shown that there is a large difference in the b-value between young and adult fish and between females and males (Chen et al., 2018; Haniffa et al., 2006; Hossain et al., 2012; Sheikh and Ahmad, 2018). The study found that the species in this study had b-values that differed from those in other studies (Huo et al., 2012; Zhang et al., 2016; Sui et al., 2015; Chen et al., 2018), and that the same species of fish had different b-values in different ecological environments, and this difference could be attributed to a combination of one or more of the following factors: (a) differences in the number of specimens tested, (b) differences in fish habitat environment, (c) sex, (d) seasonal effects, and (e) differences in the observed length range of the specimens (Froese, 2006; Hossain et al., 2009; Sani et al., 2010; Borah et al., 2018). In addition, the b-value of Schizothorax irregularis was calculated to enrich the information in the fish database in this study. This study provides basic information on the LWRs of eight plateau indigenous fish species from Xinjiang rivers. These results have important implications for the conservation of biodiversity and sustainable management of endemic fish population resources in Xinjiang.

We would like to thank our colleagues of the Fishery Department. Thanks to for LGPSC providing the language touch-ups for this article.

The authors thank the National Natural Science Foundation of China (31360635) and the Ministry of Agriculture and Rural Affairs’ financial special project (Investigation of Fishery Resources and Environment in Key Waters of Northwest China) for providing funds for this study.

This research was conducted in accordance with ethics committee procedures of animal experiments.

The authors have declared no conflict of interest.