MIGRATION ROUTES AND SPAWNING LOCATIONS OF ADULT SEA LAMPREYS IN THE HURON-ERIE CORRIDOR

Sea lamprey populations increased dramatically in Lake Erie in 2009 and have since remained well above target levels despite intensified control efforts. An emerging hypothesis to explain increased sea lamprey abundance in Lake Erie and resilience to traditional control methods is that sea lamprey recruitment and survival have recently increased in the Lake Huron-to-Lake Erie Corridor (i.e., St. Clair and Detroit rivers, Lake St. Clair, and tributaries, hereafter HEC). Despite increased efforts to control known sea lamprey producing streams and identify any new sources, adult sea lampreys have continued to proliferate in Lake Erie. This suggests that increased recruitment of sea lampreys to Lake Erie from the HEC may be an important source and recent phenomenon, perhaps triggered by recent fish habitat restoration efforts, improved water quality, or both. Indeed, larval assessments by DFO and USFWS during 2012–2014 have shown that larval sea lampreys are broadly distributed in low densities over much of the HEC. Due to the area and volume of larval sea lamprey habitat in the HEC, alternative (non-lampricide) control strategies (e.g., sterile male releases, interception traps, push-pull strategies) may be important to the future of sea lamprey control in the HEC. Emerging technologies (e.g., pheromones, alarm substances, electrical guidance) offer hope to improve the ability to capture and assess sea lamprey populations within the HEC, but knowledge of migration routes, spawning locations, and adult abundance will be necessary to direct any future alternative control efforts and to facilitate timely implementation when alternative technologies become available. We propose to use acoustic telemetry to determine the spatial distribution of adult sea lampreys during upstream migration and spawning within the HEC. A pilot study conducted during 2014 suggested that most sea lampreys in the HEC spawned in the St. Clair River, but receiver coverage limited inferences to large regions of the study area, and larger sample sizes are needed to obtain estimates with useful levels of precision. Recent telemetry studies in the St. Marys and Mississagi rivers have also shown that telemetry is well-suited to inferences about migration pathways and spawning locations.