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When aiming to protect multiple species within a single MPA, it is necessary to consider the migratory patterns and mobility of such species. A very mobile fish population would have a faster biomass exchange rate from within the MPA to outside of it, rendering an MPA less effective than it would be for a less mobile species that was is less likely to move outside of the MPA. Also MPAs must be placed along the axis of movement for populations as opposed to perpendicular. This increases the time the fish will remain within the MPA and therefore decreases the likelihood of being caught. (Watson, Alder, Walters, 2000)
Difficulties arise when trying to use MPAs to protect highly migratory species. It would be inefficient and controversial to try to place an MPA to cover the entire migration path of a population. Therefore in order to target a migratory species one possiblity is the implementation of dynamic MPAs. By tracking indicators of concentrations of the migratory fish population such as ocean fronts, the boundaries of the MPA can be changed regularly to keep up with the population. With an everchanging boundary, however, confusion as to what is or is not allowed the exact location of the MPA can develop leading to problems for fishermen and those trying to regulate the MPA. (Hyrenbach, Worm, Fonteneau, Gilman, 2007)
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