Monster Seminar JAM - Food web and landscape perspectives on non-native predator introductions in lakes
Dr. Jake Vander Zanden, Assistant Professor, Center for Limnology, Department of Zoology, Univeristy of Wisconsin, Madison
Non-native piscivores such as smallmouth bass and rock bass continue to expand their geographic range in North America. Piscivore introductions can dramatically reduce minnow abundances, causing food web disruption in which native predators such as lake trout shift to low quality, invertebrate-based diets. Adopting a food web perspective allows for an understanding of trophic interactions between native species and introduced piscivores. There is a need to identify which lakes and regions are vulnerable to future piscivore introductions. I present spatially-explicit models that predict future occurrences and impacts of bass in Ontario, with the goal of identifying vulnerable lakes in order to better guide prevention efforts. Artificial neural networks were used to identify lakes with the greatest potential to support bass. Food web studies using stable isotopes indicate that in lakes containing pelagic prey fishes (e.g., cisco, whitefish, smelt), lake trout are buffered from top-down impacts of bass on minnow populations. In the absence of pelagic prey fishes, the trophic niche of lake trout depends on the presence of bass; lake trout feed on minnows in the absence of bass, and shift to zooplankton in their presence. Lakes were classified according to their vulnerability to bass invasion based on these two models, and mapped in a Geographic Information System (GIS). Only 48 lakes (5%) were classified as vulnerable - predicted to be invaded and impacted by bass. Based on this analysis, efforts to minimize piscivore impacts can be optimized by focusing on this vulnerable subset of lakes. This general approach can be used in the proactive management of other exotic invasive species.
Date and Time:
October 14, 2004,
11:00 am - 12:30 pm