老虎潭水库鱼类群落结构特征、营养等级及鲢、鳙生长特性研究

Characterization of the Hypophthalmichthys molitrix and Aristichthys nobilis Communities and Assessment of Trophic Status in Laohutan Reservoir

研究老虎潭水库鱼类资源现状、群落结构特征、营养级及主要鱼类生长特性,为水质生物调控提供基础资料。2015年2月、5月、8月和11月利用漂流混合刺网、笼壶(地笼网)和抛撒抄网采集鱼类样本,对水库鱼类资源进行了系统调查。共发现鱼类35种,隶属于4目9科。其中,鲤形目28种,占总数的80%;鲇形目和鲈形目各3种,分别占总数的8.6%;合鳃目1种,占总数的2.8%;优势种有6种,分别为鳙、鲢、翘嘴鲌、鲫、黄尾鲴和伍氏半。鲢的全长、体重生长方程分别为:L_t=110.533[1-e^(-0.386(t+0.227))]、W_t=25.138[1-e^(-0.265(t+0.136))]^(3.118),鳙的全长、体重生长方程分别为:L_t=93.042[1-e^(-0.415(t+0.223))]、W_t=12.257[1-e^(-0.415(t+0.223))]^(2.756)。老虎潭水库鲢、鳙体重增长速度以1~3龄较高,3龄以后逐渐降低,鲢、鳙体重生长拐点分别为2.721龄和2.223龄。为最大程度发挥鲢、鳙洁水保水功效,建议起捕年龄均为3龄。碳、氮稳定同位素分析结果显示:老虎潭水库2种食物源的δ^(13)C值跨度范围为-28.99‰^-24.32‰、δ^(15)N值跨度范围为5.06‰~8.19‰,浮游植物的δ^(13)C、δ^(15)N值均大于有机碎屑。26种消费者δ^(13)C值跨度范围为-27.07‰^-20.42‰,平均(-24.76±1.54)‰;δ^(15)N变化范围为8.93‰~14.88‰,平均(12.03±1.47)‰。营养级分析结果显示,26种消费者的营养级从2.18到3.61,分属于2个营养级,且与其食性特征有较好的一致性。

Laohutan Reservoir, located in Huzhou City of Zhejiang Province, is the primary drinking water source of Huzhou City. In 2011, the fish community was altered to slow the eutrophication rate of Laohutan Reservoir by releasing filter-feeding and detritivorous fish. In this study, we characterized the fish community, the status of fish resources and eutrophication, and measured growth rates of the primary fish in Laohutan Reservoir. The objective was to provide data to improve biological control of water quality. In February, May, August and November of 2015, a systematic fishery investigation was conducted in the reservoir. Fish samples were collected using different sized fishing nets and all fish collected were weighted and identified. The age of Aristichthys nobilis and Hypophthal- michthys molitrix were determined by counting scale annuli. Aquatic snails, phytoplankton, zooplankton and organ- ic detritus samples were also collected. To understand the trophic level of fish in Laohutan Reservoir, stable isotope data （~5 N and 313 C ） for 28 aquatic animals was collected in May, including two base food sources and 26 consum- ers. A total of 35 fish species were collected, belonging to 4 orders and 9 families. Among them, Cyprinidae （28 species） accounted for 80 % of the species, followed by Siluriformes （3 species）, Perciformes （3 species） and Synbranchiformes （ 1 species）, accounting for 8.6%, 8.6% and 2.8% of the total fish species, respectively. Six dominant fish species were identified based on the index of relative importance： Aristichthys nobilis, Hypophthal- michthys molitrix, Culter alburnus, Carassius auratus, Xenocypris davidi and HemiculterUa wu. The growth rate e-quations for total length and weight tor H. molitrix were highest weight growth rate for both species occurred during years 1 - 3, and then decreased gradually, with the growth inflexion points at the age of 2. 721 and 2. 223, respectively. To achieve the maximum water quality benefit by H. molitrix and A. nobilis, the catchable age should be set at 3 years. Stable carbon and nitrogen isotope analy- sis shows that the ranges of δ13C and δ15N values for the two base food sources were -28.99‰ -24.32‰ to and 5.06‰ - 8.19‰, respectively, with higher δ13C and δ15N values for phytoplankton than for organic debris. The δ13C and δ5N values of 26 consumers varied respectively from -27.07‰ to -20.42‰ and from 8.93‰to 14. 88‰, with an average value of （ -24.76 ± 1.54）‰ and （12.03±1.47）%o. The trophic level among the 26 consumers varied from 2.18 to 3.61, indicating two levels and consistent with known feeding characteristics.