The results of nested clade analysis and the ecological
and hydrographic differences across the northern Gulf
are compatible with the notion that semi-isolated
assemblages of red snapper occur in the northern Gulf.
Because many of the hydrographic parameters, including
those that impact ecological parameters, likely vary
over long periods of time, such semi-isolated assemblages
might exist over the short term, yet over the long
term comprise a larger metapopulation tied together by
periodic dispersal. This model of metapopulation
structure differs from that of Levins (1969, 1970) with its
emphasis on extinction and recolonization, and more
closely follows the model proposed by Kritzer and Sale
(2004) where a metapopulation is viewed as a network of
partially closed populations that can influence one another’s
demographics via intermittent gene flow. Such a
model, where discrete local populations are self-replenishing
but where non-trivial demographic influences
from other populations occurs periodically, may be a
common situation in marine systems (Kritzer and Sale
2004) and clearly would impact critical fishery resource
parameters such as population size, age structure, and
recruitment.