Passive integrated transponger tags are used to monitor individual fish. The tag, 12 mm long, is inserted in the fish's body cavity and contains a microchip programmed with individual fish ID codes. The system yields information about passage times of individuals at pittag observation sites.
Release cohorts were formed by combining releases from up to 3 consecutive days to achieve observed sample sizes of at least 28 individuals. 57 cohorts were constructed from 89 releases over 4 years.