Use of natural and created Spartina alterniflora salt marshes by fishery species and other aquatic fauna in Galveston Bay, Texas, USA

We compared densities of nekton and infauna among 5 natural and 10 created (3 to 15 yr in age) salt marshes in the Galveston Bay system of Texas to test whether these marshes were functionally equivalent. Decapod crustaceans dominated the nekton on the marsh surface during both the spring and the fall. Densities of daggerblade grass shrimp Palaemonetes pugio, the most abundant decapod, were not significantly different among marshes, but the size of these shrimp in created marshes was significantly smaller than in natural marshes. Densities of the marsh grass shrimp Palaemonetes vulgaris and of 3 commercially-important crustaceans (white shrimp Penaeus setiferus, brown shrimp Penaeus aztecus, and blue crab Callinectes sapidus) were significantly lower in created marshes than in natural marshes. Gulf menhaden Brevoortia patronus were the most abundant fish collected, mainly on nonvegetated bottom adjacent to marsh habitats. Fish densities within vegetation (predominantly gobies and pinfish Lagodon rhomboides) were significantly lower in created marshes than in natural marshes. Natural and created marshes, however, did not differ in species richness of nekton. Sediment macro-organic matter and density and species richness of macroinfauna (mainly polychaete worms) were all significantly lower in created marshes than natural marshes. There was a positive relationship in created marshes between marsh age and sediment macro-organic matter, but marsh age was not related to nekton densities. Natural marshes were similar in having low elevations and flooding durations between 74 and 80% of the year; while created marshes were flooded from 43 to 91% of the time. In contrast to marsh age, tidal flooding was often related to nekton densities in marsh habitats. We conclude that marsh elevation and tidal flooding are key characteristics affecting use by nekton and should be considered in marsh construction projects.