捕捞对长山群岛海域渔业生态系统的影响

Impact of fishing on fishery ecosystem:A case study in Changshan archipelago area

为了评价捕捞对渔业生态系统的综合影响程度,建立渔业生态系统保护管理决策支持系统,本文基于状态、压力和生物群落响应PSR模型、利用层次分析法构建了捕捞对渔业生态系统的影响评价模型,包含渔船数量、捕捞压力指数、渔获量、底层鱼类比重、营养级、优势种单体重量、经济鱼类渔获量、多样性指数、均匀度指数3个层次9个指标,并选择1987—1988年和2006—2007年长山群岛游泳生物调查数据对其进行了定量评价。结果表明:近20年来,在捕捞强度不断增加的压力下,渔业生态系统的结构和功能发生显著变化,长寿命、高营养级的肉食性鱼类生物量下降明显,系统以短寿命、小型鱼类占优势;鱼类资源量、底层鱼类比重、营养级、优势种单体重量、经济鱼类渔获量、多样性指数、均匀度指数年退化率分别为4.75%、3.64%、0.31%、4.28%、2.32%、0.39%、1.14%;通过模型评价,渔业生态系统健康指数为0.34,低于评价等级Ⅲ级,说明近20年捕捞导致长山群岛渔业生态系统处于不健康状态。

In order to evaluate the comprehensive impact of fishing on fishery ecosystem, and to establish a decision support system for the protection and management of this ecosystem, an impact evaluation model of fishing on fishery ecosystem was constructed, based on the PSR （pressure-state-response） model and by using analytic hierarchy process （AHP）. The constructed model included 3 hierarchies and 9 indices （quantity of fishing vessels, fishing pressure index, fish catches, bottom fish rate, fish trophic level, single weight of dominant fish species, economic fish catches, diversity index, and evenness index）, and applied to quantitatively evaluate the fishery ecosystem in Changshan archipelago area, based on the investigation data in 1987-1988 and 2006-2007. The results indicated that with the increasing fishing pressure in past twenty years, the ecosystem structure and function in study area shifted drastically, with the biomass of long-lived, high trophic level, and piscivorous fishes declined while short-lived and small fishes dominated gradually. According to the model and the degradation rate such as fish resources （4.75%）, bottom fish rate （3.64%）, fish trophic level （0.31%）, single weight of dominant fish species （4.28%）, economic fish catches （2.32%）, diversity index （0.39%） and evenness index （1.14%）, the fishery ecosystem health index （0.34） was below the evaluation grade III, showing that the fishery ecosystem in Changshan archipelago area was in unhealthy state in past twenty years.