鲢鳙鱼养殖小型水库底栖动物群落季节动态

底栖动物是鱼类重要的天然饵料,评估水体中底栖动物的现存量可以指导渔业生产中鱼类的放养数量。为了探究淡水生态养殖水库中底栖动物群落的季节动态,于2013年4月、7月、10月和2014年1月对三河水库的底栖动物群落进行了调查分析。研究共采集到7个属的底栖动物,隶属于颤蚓科、摇蚊科和蠓科,未采集到软体动物。相对重要性指数(IRI)计算结果表明,菱跗摇蚊属Clinotanypus(IRI=7136)、颤蚓属Tubifex(IRI=6734)和尾鳃蚓属Branchiura(IRI=1384)是优势类群,分别占总捕获数量的34.26%、50.38%和10.96%。不同季节之间底栖动物的总密度和生物量差异显著(P0.05),均为冬季春季夏季秋季。冬季总密度(4100个/m~2)和总生物量(10.14 g/m~2)最高,春季(1446个/m~2;1.07 g/m~2)次之,夏季(579个/m~2;0.66 g/m~2)较低,秋季(492个/m~2;0.64 g/m~2)最低。非度量多维尺度分析(MDS)和群落相似性分析表明底栖动物群落结构季节差异显著(P=0.001),2013年三河水库的底栖动物群落可明显划分为3个:春季群落、夏秋季群落和冬季群落。皮尔森相关分析表明,底栖动物总密度与溶氧和营养盐呈正相关关系,与其他水理化因子呈显著负相关关系(P0.05)。冗余分析表明,氨氮、盐度、pH和浊度是三河水库底栖动物群落季节差异的显著影响因子(P0.05),总氮对底栖动物群落的季节差异具有边缘显著影响(P=0.08)。

Seasonal dynamics of zoobenthos communities in a small reservoir stocked with silver and bighead carp

Zoobenthos is an important natural food resource for fishes. Assessing the standing crop of zoobenthos in water bodies can provide the guideline for stocking fishes in fishery production. To explore the seasonal dynamics of zoobenthic communities in freshwater aquaculture reservoirs, investigations were conducted in April, July, and October 2013, and January 2014, to determine the composition of zoobenthic communities in the Sanhe Reservoir. The relationships between zoobenthic communities and environmental factors (water temperature, pH, turbidity, salinity, dissolved oxygen, chlorophyll a, NH₄⁺-N, NO₃^- -N, total nitrogen, and total phosphorus) were analyzed. In this study, seven genera of zoobenthos belonging to Tubificidae, Chironomidae, and Ceratopogouidae were detected. The results of the index of relative importance (IRI) showed that Clinotanypus (IRI=7136), Tubifex (IRI=6734), and Branchiura (IRI=1384) were dominant groups, which accounted for 34.26%, 50.38%, and 10.96% of total abundance, respectively. The total density and biomass of zoobenthos significantly varied among seasons (P < 0.05), and both were highest in winter (4100 ind./m² , 10.14 g/m²), followed by spring (1446 ind./m² , 1.07 g/m²), and summer (579 ind./m² , 0.66 g/m²), and were lowest in autumn (492 ind./m² , 0.64 g/m² , respectively). The zoobenthic communities in the Sanhe Reservoir mostly consisted of oligochaetes and chironomid larvae, which exhibited characteristics of higher density and lower biomass. Tubifex was the most dominant group in spring. Tubifex and Branchiura were dominant groups in summer and autumn. Chironomidae and Tubifex were dominant groups in winter. Significant differences in zoobenthic communities among seasons were found by non-metric multi-dimensional scaling (MDS) and similarity analysis (P =0.001). Zoobenthic communities in the Sanhe Reservoir showed three temporal communities, i.e., spring community, summer-autumn community, and winter community. Pearson correlation analysis indicated that total density of zoobenthos was positively correlated with dissolved oxygen and nutrients. However, the total density of zoobenthos had significant negative correlations with water temperature, pH, salinity, turbidity, and chlorophyll-a content (P < 0.05). Redundancy analysis suggested that NH₄⁺-N, salinity, pH, and turbidity were important factors, which had significant effects on seasonal variation of zoobenthic communities (P < 0.05). Total nitrogen concentration had marginally significant effects on seasonal differences of zoobenthic communities (P =0.08). In the pelagic zones of the small reservoir stocked with higher density of fishes, organism deposition resulted in a narrower habitat for the distribution of molluscs, such as shellfish and snails. Therefore, the composition of benthic fauna was dominated by oligochaetes and insect larvae. The differences in predator pressure on zoobenthos caused by fishes in different seasons had direct effects on the seasonal dynamics of zoobenthic communities in the fish stocked reservoir. In addition, the distribution of some benthic feeding fish, such as Pelteobagrus fulvidraco, might lead to the decrease in zoobenthos density in the reservoir.