PARENT SESSION
Symposium #9: Uncertainty and information in ecological forecasting.
Organized by: JS Clark and C Brewer
Tuesday, August 6. 8:00 AM to 11:30 AM. Crystal Ballroom, TCC.
Using PVA for management in light of uncertainty: effects of habitat, hatcheries, and harvest on salmon viability.
Ellner, Stephen1, Fieberg, John*,2, 1 Cornell University, Ithaca, NY, spe2@cornell.edu2 Northwest Indian Fisheries Commission, Olympia, WA, jfieberg@nwifc.wa.gov
ABSTRACT- Population viability analyses (PVA's) are frequently used by conservation biologists and wildlife managers to quantify the level of risk associated with various populations and also to examine the relative benefits of alternative management actions. Typically model predictions are extremely sensitive to estimated parameters, resulting in risk estimates that are very imprecise. Therefore, careful consideration of uncertainty is warranted when reporting PVA predictions. Here we survey some simple and general methods for assessing the uncertainty in model-based forecasts. We introduce the concepts and methods in the context of making predictions from a linear regression model. We then illustrate how these methods can be used for incorporating parameter uncertainty when reporting estimates of extinction risk, using a PVA model developed from data on Pacific Chinook salmon stocks. Several researchers have suggested that although estimates of extinction risk and population growth rate are highly variable, relative assessments between management options will be more stable. We illustrate how one can also quantify the uncertainty in relative assessments in a rigorous way. Throughout, we illustrate these methods using models relevant to the life cycle of Pacific salmon, with the intent of assessing the relative influences of habitat, harvest, and hatcheries on the viability of salmon populations. However, the same approaches are applicable to most situations where a model with estimated parameters is being used for forecasting or comparing management options.
KEY WORDS: uncertainty, PVA, salmon, viability