Diet analysis of predator fish in Otsego Lake prior and subsequent to walleye (Sander vitreus) stocking; day vs. night, 2004

Otsego Lake (42o 41’N-70o’W) is the headwaters of the glacially-created Susquehanna River valley within the northern Appalachian Plateau. Historically considered oligo-mesotrophic, (Harman et al., 1997) the unauthorized introduction of alewives (Alosa pseudoharengus) in 1986 (Foster 1989) affected the lake, creating changes similar to those of eutrophy (Harman et al. 2002). Efficient planktivores, alewives shifted species dominance in Otsego Lake from predominately large bodied crustaceans to smaller Bosmina sp. and rotifers (Warner 1999). Concurrent with the increasing alewife abundance, water transparency declined due to the lack of zooplankton grazing on algae. Increased algae levels causes depressed hypolimnetic oxygen concentrations during summer stratification. This is a result from decomposing algae in the hypolimnetic zone.