Tracking Diel Vertical Migration Differences Between Kokanee (Oncorhynchus nerka) and Their Prey

Predator prey interactions in lake ecosystems often involve contrasting diel vertical migrations. For example, when Kokanee are present, zooplankton frequently migrate below the photic zone during the day and into the epilimnion at night to feed, thereby reducing predation risk from sight feeding Kokanee. Quantifying these predator/prey interactions is essential to understand availability of the Kokanee food resources; sampling techniques must be adapted to this diurnal pattern. In Buffalo Lake, Kokanee are the primary pelagic and planktivorous fish species. We have employed hydroacoustic surveys in addition to net pulls and profile pump sampling to quantify zooplankton densities and migration patterns. Our goal is to apply realistic measures of food availability for bioenergetics modeling of Kokanee carrying capacity to guide fishery management decisions.