红树林种植-养殖耦合系统的养殖生态容量

Assessment of ecological carrying capacity of intertidal mangrove planting-aquaculture ecological coupling system

养殖容量是渔业可持续发展的核心。根据2008年10月至2009年8月的数据,构建了红树林种植-养殖耦合系统的生态通道模型(ECOPATH),利用该模型分析了耦合系统的能量流动和系统特征,并估算了该系统的养殖生态容量。结果表明,红树林种植-养殖耦合系统生态通道模型由14个功能群构成,各功能群的营养级范围为1.00～3.05。系统内各营养级间的平均能流效率为6.9%,其中7.2%来自碎屑,6.6%来自于初级生产者,能流转化效率低的原因在于系统大部分能量回流至碎屑,表明系统主要以碎屑食物链为主要能流通道。系统的特征统计学参数:总初级生产量/总呼吸量(TPP/TR)为8.021,结合较低的系统连接指数(CI=0.243)、Finn'循环指数(FCI=0.26)和能流平均路径(MPL=2.139),综合表明该生态系统尚处于发育初期。滩涂红树林种植-养殖耦合系统中主要养殖品种为尼罗罗非鱼(Oreochromis niloticus)、草鱼(Ctenopharyngodon idellus)、鲢(Hypophthalmichthys molitrix)和鳙(Aristichthys nobilis)。本研究定义养殖生态容量为不显著改变生态系统食物网结构或能流通量时的最大现存量。结果表明,系统中尼罗罗非鱼、草鱼、鲢和鳙的养殖生态容量分别为5.82t/hm2、1.81t/hm2、2.62t/hm2和4.76t/hm2。

Carrying capacity is critical for the sustainable development of fishery. Based on the data obtained from bimonthly surveys during the period from October 2008 to August 2009,a trophic model of a mangrove planting-aquaculture coupling system was constructed by using the ECOPATH model with Ecosim software. Energy flows and ecological carrying capacity（ ECC） of the coupling system were analyzed and evaluated. The results showed that the constructed ECOPATH model consists of 14 functional groups,with the trophic level ranging from 1.00 to 3.05. The geometric mean of the trophic transfer efficiencies was 6.9%,with 7.2% from detritus and 6.6% from primary producers within the system. The lower efficiencies were attributable to that most energy flows back to detritus,suggesting that the food web was more dependent on detritus than on primary producers to support fishery. The ecosystem attributes statistics：TPP/TR（ total primary production / total respiration） was 8.021,together with low connectivity index （CI） being 0.243,Finn’s cycling index（ FCI） being 0.26 and mean path length（ MPL） being 2.139,indicating this system is at a development stage according to Odum’s theory. Furthermore,we estimated the carrying capacity for tilapia（ Oreochromis niloticus）,grass carp（ Ctenopharyngodon idellus）,silver carp（ Hypophthalmichthys molitrix） and bighead carp（ Aristichthys nobilis）,which are the main cultured species in the system. The ECC was defined as the maximum biomass that a specified environment can support without significant change of major energy fluxes or structure of the food web. The ECC of tilapia,grass carp,silver carp and bighead carp culture should be 5.82 t/hm2,1.81 t/hm2,2.62 t/hm2 and 4.76 t/hm2,respectively in the system. Furthermore,the effects of uncertainty of input parameters and sensitivity analysis of the ECOPATH were also explored.