University of Rhode Island, Graduate School of Oceanography, Narragansett, Rhode Island 02882, USA.
Ecol Appl. 2013 Mar;23(2):374-91. doi: 10.1890/12-0877.1.
The ecosystem approach to management requires the status of individual species to be considered in a community context. We conducted a comparative ecosystem analysis of the Georges Bank and North Sea fish communities to determine the extent to which biological diversity is restored when fishing pressure is reduced. First, fishing mortality estimates were combined to quantify the community-level intensity and selectivity of fishing pressure. Second, standardized bottom-trawl survey data were used to investigate the temporal trends in community metrics. Third, a size-based, multispecies model (LeMans) was simulated to test the response of community metrics to both hypothetical and observed changes in fishing pressure in the two communities. These temperate North Atlantic fish communities have much in common, including a history of overfishing. In recent decades fishing pressure has been reduced, and some species have started to rebuild. The Georges Bank fishery has been more selective, and fishing pressure was reduced sooner. The two communities have similar levels of size diversity and biomass per unit area, but fundamentally different community structure. The North Sea is dominated by smaller species and has lower evenness than Georges Bank. These fundamental differences in community structure are not explained by recent fishing patterns. The multispecies model was able to predict the observed changes in community metrics better on Georges Bank, where rebuilding is more apparent than in the North Sea. Model simulations predicted hysteresis in rebuilding community metrics toward their unfished levels, particularly in the North Sea. Species in the community rebuild at different rates, with smaller prey species outpacing their large predators and overshooting their pre-exploitation abundances. This indirect effect of predator release delays the rebuilding of community structure and biodiversity. Therefore community rebuilding is not just the sum of single-species rebuilding plans. Management strategies that account for interspecific interactions will be needed to restore biodiversity and community structure.
生态系统管理方法要求在群落背景下考虑单个物种的状况。我们对乔治斯银行和北海的鱼类群落进行了比较生态系统分析，以确定在减少捕捞压力时生物多样性恢复的程度。首先，结合捕捞死亡率估算值来量化群落层面的捕捞压力强度和选择性。其次，使用标准化的底层拖网调查数据来研究群落指标的时间趋势。第三，基于大小的多物种模型（LeMans）被模拟，以测试群落指标对两个群落中假设和实际捕捞压力变化的响应。这些北大西洋温带鱼类群落有很多共同点，包括过度捕捞的历史。近几十年来，捕捞压力已经降低，一些物种开始恢复。乔治斯银行渔业的选择性更强，捕捞压力更早得到缓解。两个群落的大小多样性和单位面积生物量水平相似，但群落结构根本不同。北海以较小的物种为主，均匀度低于乔治斯银行。这些群落结构的根本差异不能用最近的捕捞模式来解释。多物种模型能够更好地预测乔治斯银行的群落指标变化，因为那里的恢复比北海更明显。模型模拟预测，在向未捕捞水平重建群落指标时会出现滞后，特别是在北海。群落中的物种以不同的速度恢复，较小的猎物物种超过其大型捕食者，并超过其前开发时期的丰度。这种捕食者释放的间接效应延迟了群落结构和生物多样性的恢复。因此，群落的恢复不仅仅是单个物种恢复计划的总和。需要考虑种间相互作用的管理策略来恢复生物多样性和群落结构。
