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" - HUIhPBACK SUCKER Movement Chuck McAda Movements of humpback suckers were monitored in two ways; the mark-and recapture method and following the fish using ultrasonic transmitters. Many problems were encountered with the transmitters, and ail observations in the Yampa River were short term. Although investigators using the tags in other parts of the country report ranges of up to 1000 yards in impoundments, we were only able to receive the tags at ranges of up to 150 yards. Most of the time our effective range was.even less. Our reduced range was .primarily due to the cool temperature and swift water of the Yampa. Turbidity probably had an adverse effect also. Five male humpbacks wE~re equipped with transmitters in the Yampa and two males and 1 female humpbacks were tagged in Walker Wildlife Area. The female was taggE~d in October of 1974 and has been tracked ofif and on approximately one year. All other fish were tagged this spring. The fish in Walker Wildlife Area were tagged to test the effective- Hess of_the transmitters and to establish daily movement patterns. The transmitters have also enabled us to determine that these three fish have remained in the pond instead of returning to the river. Peaks of movement for-the three fish have been mid-morning and late evening, similar to the female's movement last fall. Areas inhabited by the fish seemed to change as the summer progressed. Last fall and early this spring, the fish utilized the entire pond, using shallow water as well as deep. During the summer they stayed in the deep (7') end of the gravel pit. Perhaps they were seeking the slightly cooler water there.