Inferring the Spatial Distribution and Abundance of Migrating Sea Lampreys Using a State-Space Model

Strategies for controlling invasive, parasitic sea lamprey (Petromyzon marinus) in the Laurentian Great Lakes target the stream-based larval and spawning stages of the anadromous life cycle.  However, cost-effective strategies for control and population assessment remain elusive in large rivers.  We used acoustic telemetry to better understand the spatial dynamics of the spawning migration in two of the largest tributaries to Lake Huron.  Our specific objective was to estimate the fraction of the spawning population in each river that encounters and is captured in existing traps.  A Bayesian state-space model was used to describe the spatial distribution of spawners among the available migration pathways (channels, tributaries).  Capture data from traps were used to estimate spawner abundance throughout each system.  In the Cheboygan River, nearly all spawners reached the trap site, and we estimated that 47-73% of the spawning population was captured.  A lock-and-dam prevented movement (0- 2% of spawners) into tributaries.  In the St. Marys River, we estimated that only 52-54% of spawners reached trapping sites and that 2-5% of population were captured. These results may inform the development of new capture strategies to improve control and assessment of sea lamprey populations.