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 diet habitat associations of endangered adult Lost River suckers Deltistes luxatus and shortnose Suckers Chasmistes brevirostris ill 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 oil ambient temperature, pH, and dissolved oxygen, and water samples were collected to assess chlorophyll a concentration. Stickers moved into northern Upper Klamath Lake during June and began to leave lit late September cacti year. Kernel density estimates revealed differences in the distribution in the northern portion of Upper Klamath Lake lit 2002 and 2004. lit 2003, however, both Lost River and shortnose suckers were commonly located within and offshore front Pelican Bay, a shallow (1.0-2.0 m), ground water-influenced area of Upper Klamath Lake. This was especially obvious beginning in late July of 2003, concurrent with reduced dissolved oxygen levels (<4.0 mg/L) in the northern portion of Upper Klamath Lake that resulted from a die-off of the cyanobacterium Aphanizomenon flos-aquae. Both Lost River and shortnose suckers were generally associated with water depths greater than the mean depth (2.9 m) of northern Upper Klamath Lake. Evidence ratios did not suggest died differences in depth, temperature, dissolved oxygen, or pH at sticker locations. Both Lost River and shortnose suckers generally occupied depths greater than 2.0 m. except when suckers Sought refuge in Pelican Bay during periods of poor water quality. Despite the potential for increased avian predation, suckers appeared to benefit front moving into Pelican Bay rather than staying in areas where dissolved oxygen was low. Pelican Bay appears to he an important refugium and thus, may be important for sucker conservation.