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 5 consecutive days to achieve observed sample sizes of at least 30 individuals. 37 cohorts were constructed from 102 releases over 5 years.