Originally Posted by flyman
I never realized they were in the river either until I helped one summer with a TU with stream sampling of a local river. We used a seine and kicked up the bottom at the tail out of a large deep pool. The sample never failed to turn up numerous aquatic worms, not just one or two either. There would often be 10-20 worms in a sample. They looked like these
Just to clarify, these are indeed aquatic
worms (not 'washed in' from terrestrial soil). They are oligochaetes (same group as earthworms). They live in the sediments, occupy freshwater and marine habitats all over the world, and can be abundant in well-oxygenated streams (hundreds per square meter). Yes, great fish food.