Ecological Stability in the Context of Multispecies Fisheries

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Abstract
Recent theoretical studies suggest that disrupted communities are not persistent in the face of attempted invasions; moreover, reassembly of a persistent community is likely to prove difficult. It appears that the most likely species to invade a harvested community are those most similar to the harvested species, except in their propensity to be harvested. Most communities are not resistant to removals of top predators; large changes in species composition usually ensue. Large changes in community composition may, however, be associated with small changes in total biomass. Although there is some debate over whether natural communities are, on average, resistant, given species additions, community changes following species introductions appear to be common, especially in harvested or polluted systems where man effects a positive feedback between extinctions and invasions. There are several alternative theoretical relationships between population resilience, variability, and stress; the choices strongly depend on the underlying mathematical model. Multispecies models suggest that the relationship will depend on the relation of the population to other species. Empirical analyses have been highly deficient, primarily because of the failure to distinguish different temporal scales of variability.