Scartella cristata - Amazon S3

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than 200-km of unsuitable habitat in the Gulf of California (Riginos and Nachman 2001). The Texas coast
prior to jetty construction represented such a gap between S. cristata populations in the eastern Gulf of
Mexico and the southern Gulf/western Caribbean. This gap was a result of the mud and sand shores of
Louisiana, Texas, and northeastern Mexico and the Mississippi River plume. Establishment of suitable
habitat in the form of jetties and groins along the Texas coast seems to have removed any barriers to the
exchange of individuals between the eastern and western Gulf and raises questions regarding the role of
the Mississippi River in separating populations.
The Mississippi River plume may never have been a barrier to blenniid larval dispersal. Govoni
(1993) found that larval fishes were able to cross frontal boundaries such as the Mississippi River plume; a
finding supported by high levels of gene flow observed in this study between Florida and Galveston.
Larvae of many reef fish species, including blenniids, typically have a much broader geographical range
than do their adult counterparts (Leis 1991), which suggests the availability of suitable adult habitat plays
a major role in the genetic structure of these species. This appears to have been the case in Scartella
cristata. At least two distinct populations of S. cristata exist in the Gulf that were kept separate more by
the lack of suitable habitat in the northwestern Gulf and prevailing currents than by the Mississippi River
plume. Distribution of larvae from these populations may have overlapped along the Texas coast, but a
lack of suitable habitat prevented their interbreeding. It is unclear what impact jetty construction on the
Texas coast will have on the genetic structure of S. cristata. Jetties have facilitated these populations
mixing to a degree but current patterns appear to be an isolating mechanism by preventing homogenization
as evidenced by the distinction between Galveston and Port Aransas-South Padre Island. Further testing
of this hypothesis should be undertaken by examining recruits from multiple spawning events throughout
the year. As indicated through hatch-date analysis, S. cristata has the potential to spawn throughout the
year; however, the individuals selected for this analysis were all within the winter 1999-2000 cohort. This
means sites such as Port Aransas have the potential to undergo shifts in genetic composition with seasonal
changes in current patterns. The mismatch distributions tend to suggest otherwise, but these data may be
representative of the larger source populations and not reflect the full diversity that potentially occur in
local populations.