Date of Completion
Patricia Bresnahan; Peter Aarrestad
Field of Study
Master of Science
Winter drawdown is a common lake management tool, which alters lake ecosystems. This study was undertaken to determine if winter drawdown history and varying winter drawdown intensities influenced swim-up dates and mean daily growth rates (MDGR) of age-0 yellow perch , largemouth bass and bluegill in five small eastern Connecticut impoundments, two of which had extensive drawdown histories, two sporadic drawdowns, and the final having never been drawdown. Three different winter drawdown treatments (none, shallow, deep) were implemented. Daily ring counts on otoliths were used to determine relative swim-up dates and MDGR from a subsample of fish each year. Covariates of drawdown intensity, water temperature, zooplankton density and percent moveable sediment were also collected annually from each lake for inclusion into a set of mixed, nested models with unequal random effects covariates. Results revealed that 1) strong support for varying winter drawdown intensities causing significant changes in swim-up date or MDGR could not be found, possibly due to unexpected precipitation amounts and individual lake refill characteristics; 2) only bluegill swim-up was found to co-vary with drawdown history, with earlier swim-up dates found in drawn down lakes compared to the non-drawn down lake; 3) bluegill had MDGR differences between early and late swim-up in the two extensive drawdown history lakes and one with a brief drawdown history; and 4) reconstructed spawning periods compared against the current drawdown policy refill date showed an almost complete overlap for yellow perch and chain pickerel; some overlap for largemouth bass and no overlap for bluegill.
McDowell, Christopher P., "Winter Drawdown Effects on Swim-up Date and Growth Rate of Age-0 Fishes in Connecticut" (2012). Master's Theses. 324.