A Comparison of Nekton Assemblages from Natural and Restored Barrier Island Marshes in Terrebonne/Timbalier and Barataria Basins in Louisiana

We compared nekton assemblages from natural and restored (or constructed) barrier island marsh habitats in two major estuaries in southeast Louisiana: Terrebonne/Timbalier Bay and Barataria Bay.  We targeted barrier island marshes, because they are rapidly disappearing from natural (erosion and washover during storms) and anthropogenic causes (dredging and restoration projects).  We were particularly interested in the status of several fish species of conservation concern (SOCC).  We sampled for one year (8/07-7/08) at two restoration locations in the Terrebonne/Timbalier estuary (New Cut and Timbalier Islands).  A second year of sampling (11/08-11/09) was conducted at restoration locations on Grand Terre Island and Bay Chaland headland in the Barataria Bay estuary.  Nekton samples were collected with baited minnow traps (galvanized wire mesh and plastic jar traps) and a 3-m seine (3.2-mm ace mesh).  Both restored and adjacent natural marsh ponds and creeks were sampled bimonthly at each of the restoration locations. Environmental variables (including water temperature, salinity, DO, turbidity, tide stage, water depth, bottom type and habitat type [pond, creek, etc.]) were recorded for each sample collected.  We also recorded GPS coordinates and took digital photos at each sample site.  Fish species composition and abundance data were analyzed using CLUSTER, ANOSIM and SIMPER procedures with Primer v6 software.

Twenty-eight species were collected in traps with half (14 spp) common to both natural and restored marshes.  Seven species were unique to each category resulting in 21 species in each (natural and restored trap samples).  Sixty-four species were captured in seines in natural and restored sites, but 8 species found in each category did not co-occur in the other resulting in 56 species in each category.  We collected 4 (of the 11 listed) marine fish SOCC: Adinia xenica, Fundulus jenkinsi, Fundulus pulvereus, and Syngnathus louisianae, and the three fundulid species were in substantial numbers.  Cluster dendrograms illustrated that differences in species assemblages were generally greater between islands (locations) than they were between natural and restored marshes within each island.  The greatest differences were between estuaries (Terrebonne/Timbalier and Barataria) which could be due to geographic distribution or may have resulted from annual variation, since the Timbalier and New Cut locations were sampled during year one (2007-8) and the Grand Terre and Bay Chaland locations were sampled during year two (2008-9), and hurricanes Gustav and Ike impacted this area between the two sampling periods.