Incorporating uncertainty into management models for marine mammals

Good management models and good models for understanding biology differ in basic philosophy. Management models must facilitate management decisions de spite large amounts of uncertainty about the managed populations. Such mode ls must be based on parameters that can be estimated readily must explicitl y account for uncertainty, and should be simple to understand and implement In contrast biological models are designed to elucidate the workings of bi ology,and should not be constrained by management concerns. We illustrate t he need to incorporate uncertainty in management models by reviewing the in adequacy of using standard biological models to manage marine mammals in th e United States. Past management was based on a simple model that, although it may have represented population dynamics adequately,failed as a managem ent tool because the parameter that triggered management action was extreme ly difficult to estimate for the majority of populations. Uncertainty in pa rameter estimation resulted in few conservation actions We describe a recen tly adopted management scheme that incorporates uncertainty and its resulti ng implementation. The approach used in this simple management scheme, whic h was tested by using simulation models, incorporates uncertainty and manda tes monitoring abundance and human-caused mortality. Although the entire sc heme may be suitable for application to some terrestrial and marine problem s, two features are broadly applicable: the incorporation of uncertainty th rough simulations of management and the use of quantitative management crit eria to translate verbal objectives into levels of acceptable risk.