Changes between Version 10 and Version 11 of EwEugDealingWithOpenSystemProblems


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Timestamp:
2010-01-28 14:34:36 (10 years ago)
Author:
varunr
Comment:

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  • EwEugDealingWithOpenSystemProblems

    v10 v11  
    11== 2.5 Dealing with open system problems == 
    22 
    3 ===== Species and fisheries that cross system boundaries ===== 
     3==== Species and fisheries that cross system boundaries ==== 
    44 
    55For almost every defined Ecopath study area, there will be some species that have life cycles that take them outside the defined area for at least part of each year.  Movements (exchange) of biomass across the area boundary can be of two types: dispersal, involving unidirectional movement of organisms to and from sink and source populations outside the study area; and migration, involving regular, repeated movements into and out of the area by the same individuals.  These are fundamentally different processes, with very different policy consequences.  Dispersal acts as an extra mortality-agent and recruitment-source independent of fisheries and other impacts in the study area, while migration exposes organisms from the study area to particular risks and opportunities for part of the time, without acting as a ‘permanent’ drain or source of those organisms.