Evaluating the Effects of Urban Land Use on the Condition of Resident Salt Marsh Fish

Abstract

Urbanization can impact coastal fisheries by reducing the quality of important habitats, including salt marshes. Similarly, increased urban land use surrounding tidal creeks can impact the health of fish by changing salinities, altering habitat structure, and increasing exposure to pollution. In this study, we investigated the effects of residential urban land use on the condition of salt marsh resident fish along the northern Gulf of Mexico. Fish were sampled seasonally using minnow traps along salt marshes near the mouth of six second-order tidal creeks (three surrounded by residential development and three surrounded primarily by forest) in Alabama and west Florida. Fundulus grandis and Poecilia latipinna were the dominant species representing 65 % (n = 3588) and 15 % (n = 777) of the total number of fish caught, respectively. All F. grandis and P. latipinna were evaluated for mass, length, and length-weight relationship. A subset (745 and 367, respectively) was further analyzed for conditional measures of caloric density and liver somatic index (LSI). The mass per length relationships did not differ between urban and reference creeks for either F. grandis or P. latipinna; however, reference creeks yielded F. grandis and P. latipinna that were significantly larger. Further, F. grandis and P. latipinna had significantly lower LSI and caloric density in urban creeks compared to reference. Both species showed seasonal patterns of conditional measures that were likely related to reproduction and annual fattening cycles. Differences in fish condition between urban and reference creeks may reflect differences in food availability/quality, creek salinity regimes, and salt marsh structure.