The long-term management of metapopulations were performed through simulations for a case study based loosely upon herring to the west of the British Isles. These stocks are currently assessed and managed by management area, although there is evidence of much mixing between stocks (in terms of connectivity, migrations and exploitation). The simulations test the sustainability of fishing under two hypotheses corresponding to either discrete stocks which only mix on the feeding grounds, or where diffusion between stocks takes place, and where the assessment process assumes either discrete stocks or one metapopulation. The study showed that assessment based upon virtual population analysis could fail to detect overexploitation of stocks and to detect and distinguish between the effects of exploitation and regime shifts.
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