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A comparison of forage fish communities in relation to habitat parameters in Faka Union Bay, Florida and eight collateral bays during the wet season
  • Published Date:
    1985
Filetype[PDF - 3.79 MB]


Details:
  • Corporate Authors:
    Southeast Fisheries Center (U.S.), Beaufort Laboratory, ; Southeast Fisheries Center (U.S.) ;
  • Description:
    Forage fish communities were sampled in the estuarine bay system of the Ten Thousand Islands region of Florida in order to develop a basis for predicting changes in the fish communities in Faka Union Bay following future modification of freshwater inflow to that bay. A comparative approach was employed to relate fish community characteristics (species composition, relative abundance, size, and food consumed) to habitat characteristics (salinity, sediments, and aquatic vegetation). Surveys were conducted in July, August, and September 1982 and in February, May, June, and August 1983. (lJring each survey, 16 stations were randomly selected in Faka Union Bay (Stratum I) and also in the bays to the east (Stratum II) and the west (stratum III). Samples were collected at each statio~ with otter and surface trawls and analyzed for fish and macroinvertebrtae species composition, relative abundance, and size. Bottom cores and plant and shell material taken from each trawl were used to describe general habitat types. Additionally, fish stomach contents were analyzed to determine differences among areas as well as possible salinity-related differences in food consumed by the communities. During the rainy season, salinity was reduced more rapidly and to a greater extent in Faka Union Bay than in the system of bays to the east and west because of freshwater input from Faka Union Canal. Numbers and biomass of fish per station and numbers of certain macroinvertebrates were substantially lower in Faka Union Bay than in the other bays within the system, but Faka Union Bay does not support a taxonomically different or unique forage fish community. Habitat availability does not explain lower densities of fishes in Faka Union Bay because comparisons of average relative fish densities within 12 different habitat types revealed that, in 11 of the 12 comparisons, relative fish densities were less in those habitats within Faka Union Bay than in those same habitats elsewhere. Food availability does not appear to be a limiting factor, but variation in abundance ofa particular food type (e.g., polychaetes) may nevertheless affect the relative abundance of fishes preferring that food type. The majority of fishes were collected over a wide range of salinities. Ordination of occurrence and relative abundance of fishes with respect to salinity showed salinity "optima" that, for the dominant species collected, generally were at intermediate to high salinities rather than at low salinities. The ordination analyses should be useful for predicting which forage fishes will become more prevalent in Faka Union Bay during the rainy season, should water management policies and programs restructure inflow patterns so that salinities in Faka Union Bay approach those of bays to the east and west. However, a direct effect of salinity cannot be considered the only factor contributing to reduced numerical abundance of fish in Faka Union Bay, because during May 1983, salinities within all strata were high and similar, yet the relative abundance of fishes in Faka Union Bay was less than half that of the adjacent bays.

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