| Summary: | Several flatfish species including southern flounder (Paralichthys lethostigma)
recruit to estuaries during early life. Therefore, the evaluation of estuarine sites and
habitats that serve as nurseries is critical to conservation and management efforts. I used
biochemical condition and growth measurements in conjunction with catch-density data
to evaluate settlement sites used by southern flounder in the Galveston Bay Estuary
(GBE). In 2005, beam-trawl collections were made in three major sections of the GBE
(East Bay, West Bay, Galveston Bay), and three sites were sampled in each bay. Within
each sampling site, replicate collections were taken from 1) the marsh edge, 2) an
intermediate zone, and 3) the open bay. The average size of southern flounder collected
was between 12 and 19 mm standard length, and peak densities occurred in January and
February. Catch data indicated that numeric densities of southern flounder were
significantly greater in East Bay (2.75 per 100 m2) than in West Bay (0.45 per 100 m2) or
in Galveston Bay (0.91 per 100 m2). Habitat-specific variation in density was not found.
Otolith-based estimates of age indicated that the majority of southern flounder collected
were 35-45 days old and derived from early December to early January hatch-dates.
Growth rate differences were negligible across bays and habitats, with the average
growth rate being 0.40 mm/day (range 0.21-0.76 mm/day). RNA:DNA ratios indicated
that newly settled southern flounder in the GBE were in relatively high condition. Habitat-specific differences in RNA:DNA ratios were not observed; however, ratios were
significantly lower in West Bay (average 8.0) than in East Bay (average 9.5) or in
Galveston Bay (average 9.8), suggesting the condition of new recruits may vary across
the GBE. Findings from this study indicate that southern flounder use a variety of
habitats within the GBE during early life, and survival and recruitment success appear
favorable regardless of settlement site. As a result, recruitment success of southern
flounder may be less a function of the quality of nursery sites/habitats within the GBE
than of other factors (e.g., larval supply to the estuary).
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