Distribution and habitat associations of radio-tagged adult Lost River suckers and shortnose suckers in Upper Klamath Lake, Oregon

Radiotelemetry was used to investigate the summer distribution and diel habitat associations of endangered adult Lost River suckers Deltistes luxatus and shortnose suckers Chasmistes brevirostris in northern Upper Klamath Lake, Oregon. From 2002 to 2004, Lost River and shortnose suckers were tracked by boat, and water depth and water quality were measured at each fish location. A series of water quality monitors were deployed in northern Upper Klamath Lake to provide temporal information on ambient temperature, pH, and dissolved oxygen, and water samples were collected to assess chlorophyll a concentration. Suckers moved into northern Upper Klamath Lake during June and began to leave in late September each year. Kernel density estimates revealed differences in the distribution in the northern portion of Upper Klamath Lake in 2002 and 2004. In 2003, however, both Lost River and shortnose suckers were commonly located within and offshore from Pelican Bay, a shallow (1.0-2.0 m), groundwater-influenced area of Upper Klamath Lake. This was especially obvious beginning in late July of 2003, concurrent with reduced dissolved oxygen levels (