Characterizing the unfished oyster reef community of Sabine Lake Estuary relative to surrounding marsh edge and nonvegetated bottom habitats.

Abstract

Sabine Lake is an approximately 360 km2 estuary on the Texas-Louisiana border formed by the union of the Neches and Sabine Rivers. The estuary is unique in terms of its large oyster reef complex with no record of commercial harvest as far back as the 1960’s. However, after substantial oyster mortalities in Louisiana estuaries due to hurricane activity and freshwater releases post-Macondo oil spill, Louisiana has shown strong interest in opening their portion of Sabine Lake to supplement lost commercial harvest. The overarching goal of this research project was to describe oyster population structure and community composition of finfishes and invertebrates on this naturally functioning reef system compared to nearby nonvegetated bottom and marsh edge habitats. Live and dead oyster abundances were significantly different among seasons, with spring 2013 having the highest live oyster abundance, and fall 2011 having the highest dead oyster abundance. Approximately half (45%) of all live oyster heights measured were ≥ 80 mm, while the largest recorded height was 203 mm in spring 2013. The high abundance of large oysters collected within Sabine Lake Estuary may offer unique ecosystem services compared to commercially fished reefs with low, or scattered vertical relief. Oyster reef and nonvegetated deep (> 3m) habitats had significantly lower total faunal densities than the marsh edge habitat throughout all seasons. The highest species diversity and richness were observed in the nonvegetated deep habitat, while the oyster reef habitat had a higher diversity than both marsh edge and shallow nonvegetated habitats. The highest abundances of dominant crustaceans, transient, and resident fishes were found within the marsh edge habitat. Despite observing lower densities of organisms, our community analysis provides evidence that the oyster reef habitats support a unique community of fishes and crustaceans compared to the marsh edge and nonvegetated habitats. Characterizing and understanding the true value of the unfished oyster reef, marsh edge, and nonvegetated habitats will enhance natural resource management decisions in the future, by incorporating potential effects due to commercial fishing activities.