Modeling the establishment of invasive species: Predictions, consensus, and habitat limitations to spiny water flea, Bythotrephes longimanus

Bythotrephes longimanus is an invasive pelagic crustacean, which first arrived in North America from Europe in 1982 and can now be found throughout the Great Lakes.  Determining the suitability of a lake to Bythotrephes establishment is an important step in quantifying its potential habitat range and environmental risk.  Lake environmental conditions, fish and Bythotrephes occurrence data from south-central Ontario lakes were used to model lake conditions suitable for the survival of Bythotrephes.  Fish data included planktivorous fish species which may have direct impact on Bythotrephes, and predatory fish species which may have indirect impact on Bythotrephes and are related to the degree of human activity on the lakes.  Statistical models were developed and compared to predict Bythotrephes occurrence using four modeling approaches: linear discriminant analysis, multiple logistic regression, classification trees, and artificial neural networks.  Results indicated that using fish data in addition to environmental conditions improves model performance, and predatory fish information is more important than planktivorous fish information when predicting Bythotrephes invasion.  Predatory fish, lake elevation and lake size were ranked as the most important predictors of Bythotrephes occurrence.  Bythotrephes appears to establish more readily in larger, deeper and nutrient-poor lakes with lower elevation and fewer predatory fish.