Fish assemblage information will be qualified by using the 8 integrated metrics defined by the Index of Biotic Integrity (IBI) developed for the Sacramento-San Joaquin Drainage. The metrics developed for this region are based on two premises: 1. native fish species predominate in undisturbed habitats, and 2. salmonids are generally associated with high quality water and habitat (Moyle et al. 1986). The IBI is an effective bioassessment method because it is quantitative and provides criteria to determine whether a habitat is excellent or poor; there is no loss of information in calculating the index value, thus the metric values are available to pinpoint the ecological values that have been altered; professional judgment is incorporated in a systematic and ecologically sound manner, unlike other assessment methods such as diversity indices (Karr et al. 1986).