Abstract
Comparing fish communities inhabiting ditches and diked shorelines associated with saltmarsh impoundments in the northern Indian River Lagoon, Florida, under a variety of management and reconnection strategies would be useful for predicting which strategies best benefit estuarine fishes. Sampling fish in impoundment habitats, however, has been challenging, particularly in impoundment ditches (borrow ditches used to provide fill for dikes), where soft sediments, sticks and debris, and fringing mangroves present problems for traditional sampling gear such as seines. The effectiveness of a cast net was tested by comparing the fish assemblages collected by this gear to those collected by throw trap and seine. Cast-net efficiency in impoundment ditches was estimated to be 0.10–0.28 (i.e., fish densities from cast net sampling represented 10–28% of the true population). Although cast-net efficiency was less than that reported for throw traps and seines, species composition and sizes of fish were found to be comparable to the other gear. In addition to understanding differences in fish standing stock among habitats, measuring the ability of fishes to move through culverts that connect many impounded marshes to the estuary is important in gauging the success of reconnection efforts. The effectiveness of a modified culvert trap, which is lighter and less expensive than those previously used in impoundment studies, was tested. The culvert trap was successful at capturing fish moving through culverts in the microtidal environment of the northern Indian River Lagoon, and the retention efficiency of the trap was found to be 0.25 after 10–12-hr sets. The cast net and modified culvert trap together allow for a comprehensive understanding of the fish community in impounded marshes, and each may have applications to other sampling conditions.