Length-Weight Relationships of Twenty-Nine Native Fish Species from Hongshui River, Southern China

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Introduction
Te length-weight relationships (LWRs) of fsh are of great signifcance for studying the life history, growth, and reproduction of fsh populations [1]. Although these relationships are widely used in the study of fsh populations, the data on the length-weight relationships for many freshwater fshes are still not available [2]. Hongshui River is the mainstream of the Xijiang River system of the Pearl River basin. Its yearly runof accounts for 39% of the Pearl River basin [3]. Hongshui River is an exceptional aquatic ecosystem which is a home to 180 fsh species [4]. However, the length-weight relationships of the fsh in this area have rarely been monitored, and this study provides estimates for twenty-nine native species captured in Hongshui River, Southern China.
In this paper, the estimates of LWR parameters of the 29 native fshes from the Hongshui River, include the frst estimates for the 9 native fshes. Te authors believe that the results of the study can contribute greatly toward a better understanding of the growth patterns of fshes from Hongshui River under cascade hydropower development and can improve the accuracy of the Bayesian LWR estimates for the data-poor species.

Materials and Methods
Twenty-nine freshwater native fsh species (including nine species of native fsh that were difcult to collect and were recorded for the frst time: Acrossocheilus iridescens, Discogobio multilineatus, Erromyzon sinensis, Beaufortia kweichowensis, Pterocryptis anomala, Sineleotris chalmersi,   Journal of Applied Ichthyology Neodontobutis hainanensis, Channa asiatica or Takifugu ocellatus) belonging to seven families were collected from the Hongshui River (23°04′-26°50′N; 102.5°100′-109°30′E), which belongs to the upper reaches of the Pearl River, to analyze their length-weight relationships (LWRs). Te samples were collected using cages (0.2 m in height, 0.25 m in width, and 8 m in length, with a mesh size of 5 mm) and triple gillnets (20-40 m long, 1-3 m high, and mesh size, 2-3 cm) from June 2021 to July 2022. Te collected fshes belonged to the four orders and eight families. Te fsh were identifed at the species level according to the protocol described by Freshwater Fishes of Guangxi [5], and the scientifc names and authors of each fsh species were checked in accordance with the FishBase [2]. Te total length (TL) and weight were measured to the nearest 1.0 mm and 0.1 g, respectively. Te care and use of experimental animals complied with (Te Animal Research and Ethics Committees of Guilin University of Technology (Approval Code: GUT-2022-006; Approval Date: March 28th, 2022)) the animal welfare laws, guidelines, and policies. Te length-weight relationship was expressed by using a regression equation, W � aL b , which was ftted, where L was the total length (cm) and W was the total weight (g). Te relationship was converted into its logarithmic form, logW � loga + blogL, to compute a (the intercept) and b (the slope of the equation) [6]. Te log-log plots of length and weight were ftted to remove the outliers before linear regression analysis. Te correlation coefcient (R 2 ) and 95% confdence limits (95% CL) for parameters a and b also were calculated. Te t-test was used to analyze the diference between this study and the reference of the value. All analyses were performed in SPSS 23.0.

Results
A total of 2988 specimens from the twenty-nine native species belonging to the four orders and eight families were included in the analyses. Descriptive statistics and LWR parameters for the twenty-nine freshwater fsh species are shown in Table 1. Samples size ranges from 2.4 cm to 82.6 cm for Sinogastromyzon wui and Ctenopharyngodon idella, respectively. Te values of LWRs for all species were statistically signifcant (P < 0.001). Te b values of the regression model for LWRs ranged from 2.528 for Discogobio multilineatus to 3.456 for Erromyzon sinensis, and the coefcients of determination (R 2 ) ranged from 0.9078 for Traccatichthys pulcher to 0.9965 for Channa asiatica. Among these, no LWR estimates were available in the FishBase for the nine species, [2] (Table 1, ▲ ). Te present study provides the maximum total length for twenty species for the frst time (Table 1, * ).

Discussion
For the twenty-nine native fsh species, all the P values were extremely signifcant (P < 0.001) and the b values were within the expected range between 2.5 and 3.5 [6], which are in accordance with the previous estimates [1]. Although the LWRs presented in this study are frst estimates for most species, some of them must be taken as tentative because of the limited sample size (N < 30) and limited size range covered. According to the FishBase [2], no LWR information was available for A. iridescens, D.multilineatus, E. sinensis, B. kweichowensis, P. anomala, S. chalmersi, N. hainanensis, C. asiatica, or T. ocellatus. Tese results indicate that the models had a high degree of explanatory power for estimating the variation in LWRs, and would be a reliable resource for the Hongshui River fsh in the FishBase [2].
Te  [3,7]); but Sinogastromyzon wui showed a signifcant diference between the b value of this study (b � 3.109) and the reference value (b � 2.880, P > 0.05, [7]). However, such slight diferences could be real or be the result of sampling biases because of the diferent fshing methods used. Tere is a need to standardize the sampling procedures in order to obtain comparable results. In addition, the direction and degree of deviation of the b value were afected by the fsh growth environment and the biological productivity of plankton. High-productivity areas tend to result in b values greater than 3, while low-productivity areas tend to have b values less than 3 [8].
In conclusion, new records of the maximum total lengths of the twenty species were recorded. LWRs for the nine species are published herein for the frst time for the FishBase. Te results provide valuable information on the LWRs for twenty-nine native species, which itself is a useful resource for further fsheries research, conservation, and management of the Pearl River ecosystem.

Data Availability
Te data used to support the fndings of the study can be obtained from the corresponding author upon request.

Conflicts of Interest
Te authors declare that they have no conficts of interest.