**ABSTRACT NOT FOR CITATION WITHOUT AUTHOR PERMISSION.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 rlmclaug@uoguelph.ca or via telephone at 519-824-4120 x53620. Questions? Contact the GLFC via email at frp@glfc.org or via telephone at 734-662-3209.**

FINE-SCALE MOVEMENTS OF SEA LAMPREY NEAR TRAPS IN THE ST MARYS RIVER

R. L. McLaughlin¹, A. Rous¹, A. McLean¹, G. Bravener², T. C. Pratt³, L. M. O’Connor³, I. Imre⁴, C. Holbrook⁵, J. Barber⁶

¹Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1 Canada

²Department of Fisheries and Oceans, Sea Lamprey Control Centre, 1219 Queen St East, Sault Ste. Marie, Ontario P6A 2E5 Canada

³Department of Fisheries and Oceans, Great Lakes Laboratory for Fisheries and Aquatic Sciences, 1219 Queen St East, Sault Ste. Marie, Ontario P6A 2E5 Canada

⁴Algoma University, Department of Biology, Algoma University, 1520 Queen Street East, Sault Ste. Marie, Ontario P6A 2G4, Canada

⁵USGS, Great Lakes Science Center, Hammond Bay Biological Station, 11188 Ray Road, Millersburg, MI 49759 USA

⁶US Fish and Wildlife Service, Marquette Biological Station, 3090 Wright Street, Marquette, MI 49855 USA

January 2016

ABSTRACT:

Sea Lampreys (Petromyzon marinus) in the Laurentian Great Lakes are the target of a binational control program. Trapping of adults could be used for control if trap success was higher, especially in large rivers. At a hydrogenating station on the St. Marys River, we tested explanations for why probabilities of encounter with, and entrance into, traps were low and if increasing discharge from the generating station could increase probabilities of encounter, entrance, and overall trap success. Analyses combining acoustic telemetry and occupancy modeling revealed that encounter rates with traps are low because of a spatial (vertical) mismatch between Sea Lamprey space use and the positioning of traps. Sea Lampreys associated strongly with the river bottom and traps are located near the water surface. Increasing nightly discharge induced more Sea Lampreys to approach the downstream face of the generating station in 2011, but not in 2012. Further, it altered the vertical space use of Sea Lampreys at the face of the generating station, but not in a way that would bring Sea Lampreys closer to the traps. When discharge was high, Sea Lampreys were more likely to occur adjacent to and in front of the draft tubes and on the river bottom, and less likely to occur near the surface where traps were located. Additional video analyses of untagged Sea Lampreys at traps (an encounter) showed that upon trap encounter individuals (i) were at traps for a very short time (1-200 s), (ii) were more likely to approach the funnel opening when discharge was high than when it was low, but (iii) were no more likely to enter the trap when discharge was high than when it was low. Consequently, increasing discharge, and the behavioural changes it induced, had no appreciable affect on trap success. A complementary lab study determined that individual Sea Lampreys differ in behaviour, beyond what can be explained by differences in body size, sex, and state of maturity. These differences may influence an individual’s susceptibility to trapping. While our findings do not offer concrete solutions for improving trap success, they clarify the role that Sea Lamprey behaviour has on trap success, help managers understand why trap success is low, and provide information that could guide future research directions and management decisions about trapping for control.