projects > impacts of hydrological restoration on three estuarine communities > abstract
Assessing the Consequence of Hurricane-Induced Conversion of Mangroves to Mudflats on Fish and Decapod Crustacean Assemblages in the Big Sable Creek Complex of Southwest FloridaBy Carole C. McIvor1 and Noah Silverman2
1U.S. Geological Survey, Center for Coastal and Watershed Studies, St Petersburg, FL., USA
The Big Cape Sable Creek complex is located at the far downstream end of the Everglades restoration area, but is of interest because it naturally receives little freshwater inflow. The creek complex consists of six tidal creeks that are a mosaic of mangrove forest and mudflats (fig. 1): both habitats are inundated at high tide. Intertidal rivulets, i.e., drainage features smaller than first order creeks, also drain both habitats. Rivulets are depressions in the substrate up to 1 m deeper than the forest floor or mudflat around them. Rivulets fill earlier on flood tides and retain water later on ebb tides. Rivulets are "hotspots" for the entry and egress of fish and decapod crustaceans (shrimp, crabs) from intertidal habitats, and are a convenient location for sampling these animals with block nets (fig. 2) to compare the fish and decapod fauna leaving replicate forest and mudflat habitats. We hypothesize that forested sites will be dominated by small benthic forage fishes (e.g., gobies, killifishes) that experience a lower risk of predation within complex intertidal vegetation. Alternatively, we expect deeper mudflat sites lacking vegetation to be dominated by two groups of fishes: water column schooling fishes (e.g., anchovies, silversides), and large roving predators (e.g., subadult snappers, catfishes), both of whose movements will be unimpeded by the structural complexity of stems and roots of mangrove trees. The statistical design is a repeated measures ANOVA. The dependent variable is catch per unit effort (CPUE), the independent variable is habitat type: catch will be quantified as both numbers and biomass. We are sampling three replicate creeks, each with a forested and a mudflat site. The rivulet sites are fixed and drain an unknown area that varies with both tidal height and with location. Sampling will occur every 2 months for 12-18 months. A major challenge is defining either the area drained by each net, or the volume of water flowing through each net to refine our measurement of catch. Species composition will be compared between habitat types using an ordination technique, multidimensional scaling (MDS), followed by analysis of similarity (ANOSIM) to ascertain statistical significance of species groupings. Very preliminary analysis of the first data collected in fall 2002 indicates compositional differences in the fish faunas of the two types of intertidal habitats.
Contact: Silverman, Noah. U.S.Geological Survey; 600 Fourth Street South, St Petersburg, FL 33701, Phone: 727-803-8747, Fax: 727-803-2032, nsilverman@usgs.gov
(This abstract was taken from the Greater Everglades Ecosystem Restoration (GEER) Open File Report 03-54)
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U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 12 September, 2003 @ 12:30 PM(KP)