An assessment of fish communities existing within the GBP area will be employed to evaluate changes in fish species assemblages both spatially and temporally as a result of the GBP. The assessment will describe species abundance and diversity, as well as general condition of collected organisms. There are several advantages in using fish assemblages to assess biotic integrity of stream systems: fish are present in nearly every stream system except ephemeral systems or those with severely compromised water quality; fish communities include a range of species that represent a variety of trophic levels; fish integrate the effects of water degradation; fish are easily identifiable.