Macrophytes as Fish Habitat: The Role of Macrophyte Morphology and Bed Complexity in Fish Species Distributions
Carden, Kerilynn M.
University of Wisconsin-Stevens Point, College of Natural Resources
MetadataShow full item record
As shoreline development continues to increase at a rapid rate, there is increased concern regarding the role macrophytes play in the structural and functional integrity of littoral zones of lakes. The objectives of this study were to: (1) quantify relations between macrophyte structure and fish abundance; (2) analyze structural differences in macrophyte communities as potential fish habitat; (3) quantify relations between macrophyte bed structure and fish community structure; (4) determine if relations were consistent across lakes. Abundance, density and morphology of macrophytes were quantitatively assessed in eighteen 5 X 15m randomly selected shoreline study sites in twelve north temperate lakes using systematically placed quadrats. T-tests revealed that the abundance of a number of fish species was significantly higher in macrophyte sites verse non-macrophyte sites. Using univariate and multiple linear regression, macrophyte bed characteristics were related to fish community metrics across sites in each lake. Although there were some trends among macrophyte-fish relations, many were not consistent across lakes despite measures taken to minimize other sources of variation within lakes. Benthic fish including the Iowa darter Etheostoma exile, johnny darter Etheostoma nigrum, and yellow bullhead Ictalurus natalis abundance increased as the area of submergent vegetation, short-shrub leaf, complex leaf, and the mean submergent plant height values increased (r2 = 0.34-0.63). Abundance of other benthic fish including fantail darter Etheostoma flabellare, tadpole madtom Notorus gyrinus, and mottled sculpin Cottus bairdi decreased as the area of submergent vegetation, short-shrub leaf, short leaf, and the mean submergent plant height increased (r2 = 0.31-0.45). Bluegill Lepomis macrochirus, pumpkinseed Lepomis gibbosus, yellow perch Perca flavescens, and black crappie Pomoxis nigromaculatus abundance increased as macrophyte complexity increased, and decreased as macrophyte bed porosity increased (r2 = 0.24- 0.62) with one exception; pumpkinseed abundance decreased in relation to short-shrub leaf vegetation in one lake (r2 = 0.34). Similar to the univariate models, we were not consistently able to predict fish species distributions across lakes using multiple linear regressions. However, there were 12 significant multiple regression models in which morphological characteristics of macrophytes explained 28 to 79% of the variation in the abundance of a number of fish species. In addition to individual species analyses, fish community analyses were also analyzed in relation to macrophyte bed characteristics. Significant species-environment gradients were derived using canonical correspondence analyses (CCA) in six of twelve possible lakes. Macrophyte-fish relations were not consistent among lakes. Differences in relations were an artifact of differences in macrophyte structure or fish species present among lakes. Despite these differences, CCA analyses in 6 of 12 study lakes were able to explain 84.3 to 99.6% of the variation in species-environmental relations. A single linkage Euclidian distance cluster analysis using the presence/absence of fish species in six lakes resulted in three clusters but did not aid in being able to combine sites across lakes. Clearly macrophytes are important to fish; however the relations between macrophytes and fish are not consistent across lakes. These results suggest that future lake management likely needs to focus on lake-by-lake analysis of macrophyte-fish relations.