Drought-driven lake level decline: Effects on coarse woody habitat and fishes

Abstract

Research testing for the effects of climate change on lentic fishes has focused on changing thermal and dissolved oxygen regimes, but has often overlooked potential influences of altered lake levels on littoral habitat availability and species interactions. Natural littoral structures such as coarse woody habitat (CWH) can be critical to fishes for prey production, refuge, and spawning. Drought-driven lake level declines may strand these structures above the waterline and thereby remove them from littoral zones. A prolonged drought in northern Wisconsin, USA, allowed us to test for effects of lake level decline on CWH and the response of a fish community. During our study (2001-2009), the lake level of Little Rock Lake South declined over 1.1m and >75% of the previously submerged CWH was lost from the littoral zone. The loss of CWH coincided with the forage fish species (yellow perch, Perca flavescens) falling below detection and reduced growth of the top piscivore (largemouth bass, Micropterus salmoides). Our study highlights the importance of lake level fluctuations as a mechanism by which climate change may affect aquatic ecosystems and species interactions.