Measuring ecological and economic impacts of invasive species is necessary for managing invaded food webs. Based on abundance, biomass and diet data of autochthonous and allochthonous fish species, we proposed a novel approach to quantifying trophic interaction strengths in terms of number of individuals and biomass that each species subtract to the others in the food web. This allowed to estimate the economic loss associated to the impact of an invasive species on commercial fish stocks, as well as the resilience of invaded food webs to further perturbations. As case study, we measured the impact of the invasive bass Micropterus salmoides in two lake communities differing in food web complexity and species richness, as well as the biotic resistance of autochthonous and allochthonous fish species against the invader. Resistance to the invader was higher, while its ecological and economic impact was lower, in the more complex and species-rich food web. The percid Perca fluviatilis and the whitefish Coregonus lavaretus were the two species that most limited the invader, representing meaningful targets for conservation biological control strategies. In both food webs, the limiting effect of allochthonous species against M. salmoides was higher than the effect of autochthonous ones. Simulations predicted that the eradication of the invader would increase food web resilience, while that an increase in fish diversity would preserve resilience also at high abundances of M. salmoides. Our results support the conservation of biodiverse food webs as a way to mitigate the impact of bass invasion in lake ecosystems. Notably, the proposed approach could be applied to any habitat and animal species whenever biomass and diet data can be obtained.

测量入侵物种的生态和经济影响对于管理入侵的食物网是必要的。基于本地和外来鱼类的丰度，生物量和饮食数据，我们提出了一种新颖的方法，可以根据食物网络中每种物种减去其他物种的个体数量和生物量来量化营养相互作用强度。这样就可以估计与外来入侵物种对商业鱼类种群的影响有关的经济损失，以及入侵的食物网对进一步扰动的复原力。作为案例研究，我们测量了入侵鲈鱼Micropterus salmoides的影响在两个湖泊社区中，它们的食物网复杂性和物种丰富度以及本地和外来鱼类物种对入侵者的生物抗性都不相同。在更加复杂和物种丰富的食物网中，对入侵者的抵抗力更高，而其对生态和经济的影响则更低。该percid河鲈fluviatilis和白鱼突唇白鲑是两个物种，大多数限制入侵者，表示对保护生物控制策略有意义的目标。在两种食物网中，异源物种对沙门氏菌的限制作用高于土生土长的效果。模拟预测，消灭入侵者将增加食物网的适应能力，而鱼类多样性的增加也将在高丰度的沙门氏菌中保持抵抗力。我们的研究结果支持了生物多样化食物网的保存，以此减轻了鲈鱼入侵对湖泊生态系统的影响。值得注意的是，只要可以获得生物量和饮食数据，建议的方法就可以应用于任何栖息地和动物物种。