Growth, Mortality and Stock Assessment of Squaliobarbus curriculus (Actinopterygii: Cypriniformes: Xenocyprididae) from Lanxi Section of Qiantang River, China

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 t0 = –0.74 years were estimated. The von Bertalanffy growth function was calculated as Lt = 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 × 106 individuals and 3656.82 t, respectively.

Effects of Exposure to Four Endocrine Disrupting-Chemicals on Fertilization and Embryonic Development of Barbel Chub (Squaliobarbus curriculus)

The toxicities of 4 common endocrine-disrupting chemicals （EDCs）, 17β-estradiol （E2）, p,p＇-dichlorodiphenyldi- chloro-ethylene （DDE）, 4-nonylphenol （NP） and tributyltin （TBT）, to sperm motility, fertilization rate, hatching rate and embryonic development of Barbel chub （Squaliobarbus curriculus） were investigated in this study. The duration of sperm motility was signifi- cantly shortened by exposure to the EDCs at the threshold concentrations of 10ngL-1 for E2 and TBT, 1 μgL l for NP and 100 μgL-1 for DDE, respectively. The fertilization rate was substantially reduced by the EDCs at the lowest observable effect concentrations （LOECs） of 10 ngL-1 for E2 and TBT and 10μgL-1 for DDE and NP, respectively. Of the tested properties of S. curriculus, larval deformity rate was most sensitive to EDC exposure and was significantly increased by DDE at the lowest experimental level of 0.1 μgL-1. Other EDCs increased the larval deformity rate at the LOECs of 1 ngL-1 for E2, 10ngL-1 for TBT and 1μgL-1 for NP, re- spectively. Despite their decreases with the increasing EDC concentrations, the hatching rate and larval survival rate of S. curriculus were not significantly affected by the exposure to EDCs. The results indicated that all the 4 EDCs affected significantly and nega- tively the early life stages of the freshwater fish S. curriculus. Overall, E2 and TBT were more toxic than NP and DDE, while DDE might be more toxic to larval deformity rate than to other measured parameters. Thus, the 4 EDCs showed potential negative influ- ences on natural population dynamics of S. curriculus. Our findings provided valuable basic data for the ecological risk assessment of E2, DDE, NP and TBT.

Experimental Analysis on Allometric Growth in Spualiobarbus curriculus Larvae and Juveniles in Zhaoqing Reach of the Pearl River

Ecological experiment was conducted in this paper to study the allometric growth in Squaliobarbus curriculus larvae and juveniles from Zhaoqing Reach of the Pearl River. The results showed that after first feeding, the organs associated to swimming, feeling and feeding of larvae differentiated rapidly, and exhibited allometric growth. The head length, tail length and head height exhibited positive allometric growth, while trunk length exhibited negative allometric growth before reaching the growth inflexion point 20 d after first feeding, and positive allometric growth after the inflection point. Body height exhibited positive allometric growth both before and after the growth inflexion point at 18 d after first feeding. The inflexion points of snout length, eye diameter and post-eye head length occurred 23, 19 and 16 d after first feeding. For swimming organs, the dorsal fin, pelvic fins and anal fin exhibited positive allometric growth both before and after the inflexion point at 18, 19 and 17 d after first feeding; but the tail fin exhibited positive allometric growth before the inflexion point at 14 d after first feeding, and negative allometric growth after the inflexion point. S. curriculus larvae can possess various abilities soon after first feeding to survive at early stage due to the rapid development of swimming, feeling, feeding and other organs, which has important ecological significance to adapt to the complex external environment.

饲料铜水平对赤眼鳟幼鱼生长性能、体组成和成活率的影响

以CuSO4·5H2O为铜源,在饲粮中分别添加0、1、2、3、4、6、8、10和12 mg/kg的铜,制得实测铜含量分别为0.29、1.31、2.28、3.43、4.57、6.61、8.77、10.73和12.89 mg/kg的9种饲粮,选取810尾初始体重为(6.22±0.11)g的赤眼鳟(Squaliobarbus curriculus)幼鱼,置于27个300 L的圆柱形水族箱中饲喂56 d,每个水箱放30尾鱼,每个处理设置3个重复。结果表明,①饲粮中未添加铜(0.29 mg/kg饲料铜组)时试验鱼会出现典型的饲粮铜缺乏症状,如生长不良和骨骼畸形。②饲粮中添加4 mg/kg的铜时(4.57 mg/kg饲料铜组),试验鱼的特定生长率、蛋白质效率、肝体比、脏体比和存活率均达到最大,饲料系数达到最小(P<0.05)。③饲粮中添加12 mg/kg的铜时(12.89 mg/kg饲料铜组),试验鱼肝体比、脏体比最低(P<0.05)。④饲粮铜水平对试验鱼肥满度无显著性影响(P>0.05);饲粮铜水平对试验鱼体组成有显著影响(P<0.05);随着饲粮铜水平的升高,试验鱼肝脏和全鱼铜含量均显著升高(P<0.05),肝脏硫代巴比妥酸反应物(TBARS)先降低后升高(P<0.05),在3.43 mg/kg饲料铜组达到最低值。在饲料中添加适量铜可以提高赤眼鳟幼鱼的生长性能和免疫力,对试验鱼增重率和饲料系数进行折线回归分析以及全体铜蓄积量的二次曲线回归分析表明,赤眼鳟幼鱼饲料中铜的适宜量为3.94~4.92 mg/kg。