Publisher :
Place of publication :
Publication year : 2007
Thematic : Fisheries
Language : English
Note
A substantial shift toward use of marine
protected areas (MPAs) for conservation and fisheries
management is currently underway. This shift to
explicit spatial management presents new challenges
and uncertainties for ecologists and resource managers.
In particular, the potential for MPAs to change
population sustainability, fishery yield, and ecosystem properties depends on the poorly understood consequences
of three critical forms of connectivity over
space: larval dispersal, juvenile and adult swimming,
and movement of fishermen. Conventional fishery
management describes the dynamics and current
status of fish populations, with increasing recent
emphasis on sustainability, often through reference
points that reflect individual replacement. These
compare lifetime egg production (LEP) to a critical
replacement threshold (CRT) whose value is uncertain.
Sustainability of spatially distributed populations
also depends on individual replacement, but through
all possible paths created by larval dispersal and LEP
at each location. Model calculations of spatial
replacement considering larval connectivity alone
indicate sustainability and yield depend on species
dispersal distance and the distribution of LEP created
by species habitat distribution and fishing mortality.
Adding MPAs creates areas with high LEP, increasing
sustainability, but not necessarily yield. Generally,
short distance dispersers will persist in almost all
MPAs, while sustainability of long distance dispersers
requires a specific density of MPAs along the coast.
The value of that density also depends on the
uncertain CRT, as well as fishing rate. MPAs can
increase yield in areas with previously low LEP but
for short distance dispersers, high yields will require
many small MPAs. The paucity of information on
larval dispersal distances, especially in cases with
strong advection, renders these projections uncertain.
Adding juvenile and adult movement to these calculations reduces LEP near the edges in MPAs, if
movement is within a home-range, but more broadly
over space if movement is diffusive. Adding movement
of fishermen shifts effort on the basis of
anticipated revenues and fishing costs, leading to
lower LEP near ports, for example. Our evolving
understanding of connectivity in spatial management
could form the basis for a new, spatially oriented
replacement reference point for sustainability, with
associated new uncertainties.
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Keywords : Nesolagus timminsi
Encoded by : Pauline Carmel Joy Eje
