dc.description.abstract | 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. | en_US |