One of the goals established by the Puget Sound Partnership is to improve freshwater quality in 30 streams throughout the region, as measured by the Benthic Index of Biotic Integrity, or B-IBI.
Simply described, B-IBI is a numerical measure of stream health as determined by the number and type of bottom-dwelling creatures that live in a stream. My latest article published in the Encyclopedia of Puget Sound describes in some detail how this index works. Here’s the basic idea:
“High-scoring streams tend to have a large variety of ‘bugs,’ as researchers often call them, lumping together the benthic species. Extra points are given for species that cannot survive without clean, cool water. On the other hand, low-scoring streams are generally dominated by a few species able to survive under the worst conditions.”
Because benthic invertebrates have evolved over time with salmon and other fish, many of these important “bugs” are primary prey for the fish that we value highly. Said another way, “healthy” streams — as measured by B-IBI — tend to be those that are not only cool and clean but also very good habitats for salmon.
