**ABSTRACT NOT FOR CITATION WITHOUT AUTHOR PERMISSION. The title, authors, and abstract for this completion report are provided below. For a copy of the full completion report, please contact the author via e-mail at jessica_barber@fws.gov or via telephone at 906-226-1241. Questions? Contact the GLFC via email at frp@glfc.org or via telephone at 734-662-3209.**

ESTIMATING LAKE ERIE JUVENILE ABUNDANCE AND ASSESSING SURVIVAL OF MIGRATING JUVENILES IN THE ST. CLAIR - DETROIT RIVER SYSTEM

Jessica Barber¹, Gale Bravener², Jean V. Adams³

¹U.S. Fish and Wildlife Service, Marquette Biological Station

3090 Wright St., Marquette, MI 49855 USA

²Department of Fisheries and Oceans, Sea Lamprey Control Centre

1219 Queen St. East, Sault Ste. Marie, ON P6A 2E5 Canada

³U.S. Geological Survey, Great Lakes Science Center

1451 Green Rd., Ann Arbor, MI 48105 USA

June 2015

ABSTRACT:

Despite consecutive lampricide treatments during 2008-2009 implemented to reduce the Lake Erie population to the target level of 3,000 adult sea lampreys by 2011, the population remained well above this target level (23,000 in 2011). Increased larval assessment and barrier inspection effort during the 2011 field season did not indicate any new or unknown infestations. Recent rehabilitation efforts in the St. Clair - Detroit River System (SCDRS) have improved water quality and habitat throughout the system, possibly improving sea lamprey recruitment and survival, implicating the SCDRS as a possible source of Lake Erie parasites. However, there was uncertainty about whether recently metamorphosed or parasitic-phase sea lampreys (juveniles) can survive the migration through the SCDRS and what their contribution to the sea lamprey population in eastern Lake Erie might be. This project was designed to determine whether juveniles released in the St. Clair River can migrate successfully downstream through the SCDRS and survive to be recaptured in the eastern basin in Lake Erie, where adult traps are operated annually. The research demonstrated that juveniles released in the SCDRS do contribute to the eastern Lake Erie adult population, but to a lesser degree than those released in Lake Erie tributaries. Additionally, the overall juvenile population was higher than expected relative to the adult abundance in Lake Erie. Although results indicate that juveniles released in the SCDRS can successfully migrate to Lake Erie, more work is needed to fully evaluate the contribution of SCDRS sea lampreys to the parasitic population of Lake Erie.