Avoidance experiments with homing shoals of minnows, Phoxinus phoxinus in a laboratory stream channel

In a laboratory stream channel consisting of two tributaries joining to form a ‘river’ it proved possible to establish three populations of minnows in separate home ranges. Minnows in the apparatus avoided water with low concentrations of dissolved oxygen but returned to the home range when aerated water was re‐established. Concentrations of 4, 8 and 10 mg 1 −1 of phenol did not cause avoidance behaviors, in fact the highest concentration killed some fish, but activity levels were severely depressed and shoaling behaviors was also affected.