藕–鱼种养结合模式对藕田底栖动物的影响

Effects of integrated lotus-fish farming systems on macrozoobenthos in lotus field

低洼田因地制宜创新农作制度,构建的藕-鱼种养结合模式是一种新型高效的生态农业模式,其中底栖动物是这个复合生态系统的重要组成部分。为研究藕-鱼种养结合模式对藕田底栖动物的影响,本试验设计了3种模式(莲藕-甲鱼模式、莲藕-彩鲤模式以及莲藕-泥鳅模式),以单养甲鱼模式作为对照,于种养结合前(2013年3月)、种养结合后作物生长旺盛期(2013年8月)以及鱼类捕捞后(2014年1月)3个时期对各试验田块底栖动物进行了取样,分析种养结合前后藕田底栖动物的种类构成、密度、生物量和多样性的变化。结果表明,种养结合模式对底栖动物种类无显著影响,共采集到底栖动物6科12属13种。但藕田套养水产动物,由于水产动物活动对底泥的扰动,底栖动物多样性有所下降。种养结合模式田块水生昆虫密度、生物量以及底栖动物总密度、总生物量均较种养结合前大幅度增加。3种种养结合模式种养结合后水生昆虫密度、生物量以及底栖动物总密度、总生物量的平均增加幅度分别达到12倍、336倍、11倍和273倍。而单养甲鱼模式池塘放养甲鱼后底栖动物生物量较放养前有所减少。另外,与单养甲鱼模式相比,莲藕-甲鱼种养结合模式水生昆虫密度、生物量以及底栖动物总密度、总生物量均有所提高,而寡毛类密度、生物量则有所降低。此外,采用Shannon-Wiener多样性指数和BI生物指数(Hilsenhoff生物指数)对3种种养结合模式藕田水质进行了评价。结果表明,采用BI生物指数评价的结果与实际情况较为吻合,3种种养结合模式中水质状况以莲藕-彩鲤模式最好,而莲藕-泥鳅模式水质最差。

Integrated Agri-Aquaculture Systems（IAAS） such as rice-fish farming have been practiced for centuries in China. In these systems, on-farm wastes and by-products are recycled in relatively closed nutrient cycles. IAAS also utilizes resource efficiently and provides additional food and income to local farmers. Thus these systems are more sustainable compared with other food production systems such as monoculture systems. In the north of Jiaxing City, Zhejiang Province, a wide area of low-lying wetlands exists because of land subsidence. The permanently flooded field is not suitable for grain and oilseed rape production and thus agricultural economy development in the area is seriously restricted. As an innovation of IAAS, the trapa-fish（e.g. trapa-loach, trapa-Chinese snakehead fish and trapa-Chinese soft-shelled turtle）, lotus-fish（e.g. lotus-loach, lotus-Chinesesoft-shelled turtle and lotus-Chinese snakehead fish） and water bamboo-fish（e.g. water bamboo-loach） integrated patterns were being gradually developed in recent years. As an important ecological group in freshwater ecosystems, macrozoobenthos are important in material cycling and energy flow, and are widely used in environmental monitoring. In order to determine the response of macrozoobenthos diversity to lotus-fish farming, field experiments were conducted in Zhejiang Northbay Wetland Eco-agricultural Science and Technology Ltd. Co. Three typical integrated lotus-fish farming systems（including integrated lotus-soft-shelled turtle system, integrated lotus-Oujiang color common carp system and integrated lotus-loach system） along with one monoculture system（soft-shelled turtle monoculture system） were selected in the study. Ecological surveys of each system were carried out at three periods — before lotus-fish co-culture period（late March 2013）, after lotus-fish co-culture and the lotus in vigorous growth period（mid-August 2013） and after fish harvesting period（early January 2014）. The species composition, standing crops and diversity of samples were analyzed. Altogether, 13 macrozoobenthos taxa belonging to 6 families and 12 genera were identified from all the qualitative and quantitative samples. Results showed that there was no significant difference in the macrozoobenthos species after the adoption of integrated lotus-fish farming system. However, macrozoobenthos biodiversity decreased because of sediment disturbance caused by aquatic animals after fish stocking. The density and biomass of aquatic insects and macrozoobenthos in the integrated lotus-fish farming systems all increased after fish stocking. The average density and biomass of aquatic insects, total density and biomass of macrozoobenthos increased by 12 times and 336 times, 11 times and 273 times, respectively. However, in the soft-shelled turtle monoculture system, macrozoobenthos biomass decreased after soft-shelled turtle stocking. Meanwhile, the integrated lotus-soft-shelled turtle system had higher density and biomass of aquatic insects and macrozoobenthos compared with soft-shelled turtle monoculture system. Conversely, the density and biomass of oligochaetes in integrated lotus-soft-shelled turtle system were lower than those in monoculture system. Results of bioassessment using Hilsenhoff biotic index indicated that water quality under lotus-Oujiang color common carp system was better than that under lotus-loach system and lotus-soft-shelled turtle system.