The EPA and the Watershed Management Division (WSMD) are trying to find out. In 2013 and 2014, they teamed up to sample a subset of Vermont’s large rivers to answer this question. How do they do this? They wrestle rafts with large outboard motors down steep embankments, pile in gear and staff, and head down river. Along the way, the rafts either electroshock* fish with a custom made raft or collect aquatic life (both bugs and algae) and measure physical habitat from up to 2 km of river. Because Vermont’s large rivers are interspersed with riffles, the boats often need to be guided carefully through the shallows, occasionally pried off large rocks and sometimes ride the rapids until calmer waters prevail. Each large river takes at least one very long day to sample.
Last summer, the WSMD sampled the Connecticut River. In 2014, we will sample the Lamoille and multiple sites on the White River. Vermont regularly samples ~ 150 smaller wadeable rivers and streams as part of its yearly monitoring efforts. Until now, the large rivers have only been sampled for water chemistry, as biological monitoring was impractical. Please visit EPA’s National Aquatic Resource Survey web site to learn more!
*Electroshocking uses electricity to stun fish and is a common scientific survey method; when performed correctly it does not harm the fish, only stuns them for a few moments to allow examination.