Comparison of nekton habitats associated with pipeline canals and natural channels in Louisiana salt marshes

Abstract

Nekton of Louisiana coastal marshes was sampled approximately twice monthly between June 1990 and May 1991 (1) on marshes adjacent to canals and on natural marshes with flumes and (2} within canals and natural channels using a small trawl. Canals constructed using two different methods (flotation and push) were studied. Dagger-blade grass shrimp Palaemonetes pugio, blue crabs Caltinectes sapidus, Gulf killifish Fundulus grandis, diamond killifish Adinia xenica, brown shrimp Penaeus aztecus, and sheepshead minnows Cyprinodon variegatus dominated catches in terms of numbers and biomass on marshes as well as in canals and natural channels. Although densities of some species differed among the various sites that were sampled (e.g., dominant cyprinodonts were most abundant in creek tributaries), densities in canal and natural channel habitats were not significantly different. Predator encounter rates in canals and natural channels were similar, suggesting that the value of habitat in canals may increase over time as slumping decreases depth and steepness of bottom profiles and creates shallow subtidal refugia along the canal-marsh interface. The nurse~ function of canals open to tidal flushing is probably enhanced by the presence of fringing marshes, which provide habitat for nekton at high tide.

Temporal dynamics of fish assemblages of natural and artificial tropical estuaries

“…Clearly, the natural estuaries and the poorly connected artificial lakes differ significantly at an assemblage level, and by implication at a process level, with substantial differences in species composition indicating quite different food web structures. Taken together, the restricted connectivity (Rozas 1992), restricted circulation (Maxted et al 1997) and poor water quality (Baird & Pereyra-Lago 1992, Maxted et al 1997) typical of many artificial waterways probably diminishes their value as nursery grounds for many species. Although the proliferation of artificial waterways around the world has the potential to provide expanded amounts of estuarine habitat available to fish (Baird et al 1981, Morton 1992 and to replace degraded habitat, unless modification is managed much more carefully than in Keyatta and Curralea Lakes the outcome is likely to be diminished fish habitat quality, reduced fisheries production and degraded ecosystem function.…”

Community composition and diet of fishes as a function of tidal channel geomorphology

“…Nekton play important roles in marsh ecosystems as both prey and predators (Baltz et al 1993, Rozas & Reed 1993, Kneib & Wagner 1994, Minello et al 1994, Peterson & Turner 1994, Rozas & Zimmerman 2000, Talley 2000, West & Zedler 2000, and habitat heterogeneity is an important factor for predicting species richness and abundance of fishes (Szedlmayer & Able 1996). Adult and juvenile nekton benefit from the high productivity of the flooded marsh surface (Minello & Zimmerman 1992, Rozas 1992, Rozas & Minello 1998) and act as critical vectors in the transport of nutrients and energy (Kneib 1997, West & Zedler 2000 in the 'trophic relay' that horizontally translocates intertidal production across boundaries within the marsh system and along the estuarine gradi-ent (Kneib 2000). The relationship of tidal marsh geomorphology to nekton productivity is particularly germane to restoration of tidal marshes.…”

Nekton use of marsh-surface habitats in Louisiana (USA) deltaic salt marshes undergoing submergence

“…Estuarine marshes provide nursery habitat for numerous species of nekton (Zimmerman & Minello 1984, Rozas & Odum 1987, McIvor & Odum 1988, Hettler 1989, Kneib 1991, Rozas 1992b, and many of the species that depend on these marshes support important coastal fisheries. For example, brown shrimp Penaeus aztecus Ives are dependent on marsh-surface habitat during their postlarval and early juvenile stages (Minello & Zimmerman 1991).…”