Summer fish community of the coastal northern Gulf of Mexico: Characterization of a large-scale trawl survey

Fish were collected by otter trawl at 367 sites from 119 coastal water bodies in the northern Gulf of Mexico, ranging from north-central Florida to the Rio Grande, Texas, during the summer months of 1992-1994. The fish were identified and enumerated, and tissue contaminants (in fillets), and external abnormalities (body, buccal, branchial, and ocular) were determined. Results were compared for sites east and weft of the Mississippi River, within the Mississippi River, seven estuarine categories, and over 3 years. Approximately 31,000 individual fish were captured, representing 100 genera and 141 species. Thirteen species comprised 91 % of the total abundance; abundances of 128 species were 1% or less. Pinfish Lagodon rhomboides, Atlantic croaker Micropogonias undulatus, Gulf menhaden Brevoortia patronus, and bay anchovy Anchoa mitchilli were the more dominant species. Fourteen species were collected from at least 10% of the sites; 85 species were captured at no more than 1% of the sites. Atlantic croakers and hardhead catfish Ariopsis felis were collected more frequently (>50% of sites). Indices of community structure from the full data set ranged as follows: 2.8 for the Shannon-Wiener index, 0.90 for Simpson's index, and 0.56 for Pielou's evenness index. Chemical contaminants (predominantly total mercury and polychlorinated biphenyls [PCBs]) exceeded federal risk-based consumption guidelines in 2.7% of fillets from four species. External abnormalities occurred on 17 species and approximately 1% of the total number of fish examined. Community structural properties varied temporally across years and spatially over estuarine categories and between areas east and west of the Mississippi River. Four distinct assemblages were identified by cluster analysis of species abundance. Cluster membership was associated with salinity, depth, dissolved oxygen, water clarity, and geographic area.