PARENT SESSION
Poster Session #12: Marine Ecology.
Monday, August 5. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Assessment of tidal creek degradation and restoration on Andros Island, Bahamas, using visual faunal surveys .

Silliman, Brian^*,2, Arrington, D. Albrey^*,1, Layman, Craig^*,1, ² Brown University, Providence, RI¹ Texas A & M University, College Station, TX

ABSTRACT- We used underwater visual census methods (UVC) to characterize faunal assemblages of estuarine creeks on Andros Island, Bahamas, and used these data to evaluate efforts to restore tidal creeks. Creeks on the island have had natural tidal flow blocked by anthropogenic (e.g. road construction) or natural (e.g. hurricanes) disturbance. Culverts or bridges have been installed to maintain or restore natural tidal flow in some of the blocked creeks. We used UVC to document the presence/absence of fish and macro-invertebrate species in four habitats (flat, seagrass, mangrove, and rocky) of twenty-six estuarine creek systems. Creeks status was classified a priori as to degree of tidal blockage: completely blocked, blocked with culverts, blocked with bridge, and unblocked (i.e. natural flow). Highest species richness was in sites with natural tidal flow or bridges. Using detrended correspondence analysis (DCA), we demonstrated significant turnover in fish assemblage composition in creeks with different degrees of tidal flow. The effect of creek status (amount of tidal flow) overrode clear segregation of species among habitat types. Bridge and natural sites were clustered together in ordination space, indicating similarity in assemblage composition. Sites completely blocked or blocked with culverts were clustered together, and were separated from bridge and natural sites. Blocked sites with culverts had the most variable fish assemblages, demonstrating variable success of culverts as a means of accomplishing restoration goals. Multiple large culverts allow greatest tidal flux, resulting in assemblages most similar to those in natural creeks. Even small culverts allow fish to immigrate into otherwise isolated upstream habitat, suggesting creek system health can be enhanced without complete restoration to pre-disturbance state.

KEY WORDS: aquatic restoration, fish, community structure, estuary