Temperature and Depth Profiles of Potamodromous Rainbow Trout in Minnesota Waters of Lake Superior

Implanted archival tags were used to record temperatures and depths occupied by potamodromous rainbow trout Oncorhynchus mykiss in  the Minnesota waters of Lake Superior. Two strains of rainbow trout were tagged, including naturalized steelhead, and a domesticated strain known locally as “Kamloops”.  Between 2006 and 2009, a total of 34 steelhead and 93 Kamloops bearing archival tags were released into Lake Superior.  A $50 reward was offered to anglers for the return of tagged fish, and fish were also recaptured in traps located in the French and Knife rivers. Within the first 38 days after release, 6 steelhead and 25 Kamloops were recaptured by anglers.  After this initial period, 10 steelhead and 9 Kamloops tags were recovered.  Both strains were very surface-oriented, spending more than half their time in the top 1 m of water, and 97% of their time <10 m deep.  Diel movements were noted more often in steelhead, and repeated brief dives up to 46 m were common for Kamloops, but individuals varied greatly.  These behavior patterns are likely related to their preferred food resources.  Growth rates and survival of these fish may correlate highly with summer water temperatures and length of the growing season.