At present, we are relating fish abundance at each of our 1,000 sites to physical and chemical conditions to determine individual species' tolerance limits to certain stressors. After a careful review of literature on fish tolerances and distributions, we used physical, chemical, and geographic measures of naturally occurring stream conditions and fish abundance data to develop a model that predicts which fishes should be present in a particular stream. So when we now sample the stream, we can compare the actual fishes present to those predicted by the model. If only a few species are found when we expected 10 or 11, its time to find out what may be wrong.
Managers then have an idea of what needs to be fixed in the stream or upstream watershed.
All of this is being done using only the list of fish species present and a few simple habitat measures. According to the current model, most streams have many fewer fish species than they could have if it were not for human impacts. Estimated impacts to individual fish species are sometimes staggering. That equates to about 3,600 stream miles and about 3 million brook trout. Upstream impervious surface related to development is a pervasive impact to this species.