Evaluation of Strategies for the Release of Male Sea Lampreys ( Petromyzon marinus) in Lake Superior for a Proposed Sterile-Male-Release Program

Successful implementation of a sea lamprey (Petromyzon marinus) control technique that uses sterilized males to reduce reproduction presently depends on the importation of large numbers of males outside of the target population. Strategies were examined for releasing male sea lampreys from Lakes Michigan and Huron into the Lake Superior spawning population and the ability of these introduced males to compete with resident males and spawn with resident females. During 1987, 553 (9%) of 6,324 imported fertile males released at 12 shoreline and one offshore site in Lake Superior were recaptured. Most remained within 20 km of the release site and entered the first stream encountered. During 1988, 393 (18%) of 2,208 imported fertile males released directly into three spawning rivers were recaptured. In both cases, animals released early during the spawning run were more likely to be recaptured than those released later. Introduced males successfully competed with resident males and spawned with resident females. Demonstrating that male sea lampreys could reproduce successfully when relocated supported subsequent large-scale field trials of the sterile-male-release technique.