Comparison of Nekton Use for Cordgrass Spartina alterniflora and Bulrush Scirpus mariqueter Marshes in the Yangtze River Estuary, China

To test whether invasive Spartina alterniflora marshes were functionally equivalent to native Scirpus mariqueter marshes, the present study used bottomless lift nets (20 m2) during 12 high-tide events from August to October 2008 to compare nekton densities and biomass between the two marsh types in the Dongtan wetland. A total of eight species of fish, two species of shrimp, and three species of crab were collected. So-iny mullet Chelon haematocheilus, keeled mullet Liza carinata, Asian freshwater goby Acanthogobius ommaturus, and ridge-tail prawn Exopalaemon carinicauda dominated samples from the two marsh types and accounted for over 90% of the total catch. There were significantly greater densities and biomass (p < 0.05) of total nekton (all species combined) and two mullets (C. haematocheilus and L. carinata) in S. alterniflora marshes than in S. mariqueter marshes in August 2008, while no significant differences (p > 0.05) between the two marsh types were observed for densities and biomass of any species or total nekton in September and October 2008. Non-metric multidimensional scaling ordination did not show clear separation of samples between the two marsh types (r = 0.071, p = 0.159). Furthermore, there were no habitat-specific differences (p > 0.05) in the size distributions of the three numerically dominant species (C. haematocheilus, L. carinata, and A. ommaturus). We concluded that S. alterniflora marshes were utilized by nekton in a fashion similar to their utilization of native S. mariqueter marshes under similar physical conditions.