Small-scale patterns of nekton use among marsh and adjacent shallow nonvegetated areas of the Galveston Bay Estuary, Texas (USA)

Abstract

We quantified and compared nekton and infauna1 densities among vegetated (edge Sparhna alterniflora, inner Spartina alterniflora, Scirpus maritimus, Juncus roemenanus, and Spartina patens marsh) and shallow nonvegetated (marsh pond, marsh channel, cove, and shallow bay) areas of upper Galveston Bay and East Bay, Texas. In 2 seasons (spnng and fall) of h g h nekton abundance, and over 2 yr, we collected 267 quantitative samples (upper Galveston Bay, 1993 = 127 and East Bay, 1994 = 140) using a 1 mZ drop sampler. The vegetated marsh surface consistently contained more species (i.e. higher species richness) and total numbers of decapod crustaceans than nonvegetated areas. In contrast, fish species richness and densities of total fishes on the marsh and in nonvegetated areas were not sigrdicantly different in most comparisons. Most numerically dominant species of nekton seemed to exhibit at least some degree of habitat selection. Within vegetation, 2 factors, elevation and proximity to open water, were most important in influencing the distribution of nekton. Low marsh edge dominated by Spartina alterniflora or Sciq~us maritirnus was apparently selected by most species that used the marsh surface including brown shrimp Farfantepenaeus aztecus, blue crab Callinectes sapidus, and daggerblade grass shrimp Palaemonetes puglo. White shrimp Litopenaeus setlferus and striped mullet Mugil cephalus also were concentrated in low edge marsh; although in one comparison, densities of these 2 species in edge and Inner S. alterniflora were not significantly Uferent In contrast, gulf killifish Fundulus grandis and sheepshead minnow Cyprinodon vanegatus were most abundant on inner S. alterniflora or S. patens marsh. Other fishes (gulf menhaden Brevoortia patronus, spot Leiostomus xanthurus, bay anchovy Anchoa mitchill~, blackcheek tonguefish Symphurusplagiusa, and Atlantic croaker Micropogonias undulatus) had higher densities over nonvegetated bottoms than on the marsh surface. Specific habitat types that these pelagic species seemed to favor were marsh channels (gulf menhaden, bay anchovy), marsh ponds (spot), and coves (Atlantic croaker, blackcheek tonguefish). Overall, marsh-surface and adjacent nonvegetated habitat types contalned much higher densities of most nekton than the shallow bay. Infaunal densities were estimated from sedlment cores, and taxa (mainly annelids, crustaceans, molluscs, and insects) were most abundant in nonvegetated areas contiguous with marsh in the spring. Factors that influenced infaunal abundance are complex and may include predation, flooding patterns, elevation, and distance to edge. Our study has important implications for designing marsh-creation projects. Based on our results, we recommend creating a variety of marsh and contiguous shallow-water areas to enhance nekton biodiversity. To maximize fishery habitat, priority should be given to constructing low marsh edge by creating large areas of low marsh interspersed with a dense network of shall0.w channels and interconnected ponds.

Seasonal Estimates of Fish Biomass and Length Distributions Using Acoustics and Traditional Nets to Identify Estuarine Habitat Preferences in Barataria Bay, Louisiana

“…The differences in biomass among seasons and regions were probably influenced by physiochemical variables such as temperature and salinity, both of which varied significantly among seasons and regions during this study (MacRae 2006). These results are consistent with those of other studies that have found estuarine assemblage structure to be associated with seasonal movement and migration patterns related to environmental conditions (Rakocinski et al 1992;Rozas and Zimmerman 2000;Granados-Dieseldorff and Baltz 2008). Additionally, catches of species such as Gulf menhaden (a species that dominated our biomass estimates) are known to vary seasonally, primarily because they migrate offshore during late fall to overwinter and reproduce (Patillo et al 1997).…”

“…Few studies have focused on differences in the abundance of fish among these habitats (Coen et al 1999;Harding and Mann 2001;Lehnert and Allen 2002), particularly in Louisiana (Plunket and LaPeyre 2005). In addition to discrete habitats, seasonal and spatial variation in environmental conditions (Rakocinski et al 1992;Rozas and Zimmerman 2000;Granados-Dieseldorff and Baltz 2008) and reproductive behavior (Subrahmanyam and Coultas 1980) can influence the spatial distribution of fish biomass. Moreover, biases in the fishing gears used to collect samples can affect the observed trends in catch (Hayes et al 1996;Hubert 1996;Jackson and Harvey 1997).…”

A study of the fish community structure in a tidal creek

“…These conditions favor the presence of large populations of fish in these shallow aquatic environments along the margin of estuaries (Rozas & Zimmerman, 2000;Vidy, 2000).…”

“…They show a wide temporal variation in their species composition due to the environmental dynamics and migratory nature of most of the fish, as well as to the connection between the estuarine habitats because of their proximity and tidal flow (Rozas & Zimmerman, 2000).…”

Foraging guild structure and niche characteristics of waterbirds in an epicontinental lake in Mexico

“…Second, clumped resources attract more species and individuals. Studies suggested that shallow waters have greater organic matter and submerged plant beds, providing a rich foraging habitat and protection from predators (Rozas and Odum 1988;Minello et al 1994;Rozas and Zimmerman 2000;Castellanos and Rozas 2001;Gossman 2005;Cannaday 2006). Other studies also suggested that shallow waters can accommodate more species than deep waters (Williams 1996;Colwell and Taft 2000), which suggests that clumped and rich resources in shallow waters increase bird density there and reduce competition.…”