Fish assemblage structure in relation to environmental variation in a Texas Gulf Coastal Wetlands

ABSTRACI': We described seasooal &h--~1ages in an estuarine marsh fringing Matagorda Bay. Gulf of Mexico. HabItat zones were identified by patterns of fish species ab1JDdaDce ~d indicator &pedes opdma along graments in saJinlty. dissolved oxygen (DO). and depth in our samples. Indicators of the lower brackish zone (lower Jake and tidal bayou d ~ to the bay) were gulf!!!~den (~pGb'OnIU), bay anchovy ~ mitdrilIa), snver perch (BGirdi6ll4 dl7:ys0llrG). and spotted seatrout ( ~ fteb,IIosUI) at salinity> 15roo. DO 7-10 mg I-I. and depth < 0.5 In. Indicators of the upper brackish zone (Jake and fringing salt marsh) were pinSsh (Lapdon momboida) and spot (l.8iostorIa&I-thurw) at saJiDity 10-20roo. DO> 10 mg I-I. and depth < 0.5 m. In the freshwater wedand zone (diked wedand, ephemeral pool, and pereDDial scour pool). indicators were sheepshead minnow (CypriI1odOrI ~), rainwater 1dDifish (LIIcaftiG par-). mosquito&sh (GGmhrma affinis), and saDfiD mony (PHc:ilia latipiIIna) at salinity < 5180. DO < 5 mg I-I. and depth ~ I m. In the freshwater dlaDDeHzed zone (slough-and irrigation ~). indiQtors were three sunfish species (LepomIs). white aappie (PorIIOIiI annulariI), and gizzard shad ' (Doror- tep~) at Alinity < 5180. DO < 5 mg I-I. and depth> 1.5 m. In bnddsh zones, seasooal variation in species diversity among sites was positively correJated with temperature, but assemblage 8tnIcture also was inftuenced by depth and DO. In the freshwater zones, seasooal ~tion in species diversity among sites was posi.tiveIy correlated,nth depth, DO. and salinity. but assemblage structure was weakly associated,nth temperature. Species diversity and assemblage strucfure were strongly affected by the connectivit