Knowledge of the spatial and temporal migration dynamics of adult Sea Lamprey (Petromyzon marinus) is needed to improve population assessment and control in the Great Lakes. In Chapter 1 of this dissertation, a Bayesian state-space model provided reach-specific probabilities of movement, including trap capture and dam passage, for 148 acoustic-tagged adult Sea Lamprey in the lower Cheboygan River, Michigan, a tributary to Lake Huron. Reach-specific movement probabilities were combined to obtain estimates of spatial distribution and abundance needed to evaluate a barrier and trap complex for Sea Lamprey control and assessment. Of an estimated 21,828 - 29,300 adult Sea Lampreys in the river, 0-2%, or 0-514 untagged Sea Lampreys, could have passed upstream of the dam, and 46-61% were caught in the trap. Although no tagged Sea Lampreys passed above the dam (0/148), the sample size was not sufficient to adequately evaluate barrier effectiveness for large populations as in the Cheboygan River. For example, more than 1 643 tagged Sea Lampreys would have been needed to conclude (with 95% probability) that fewer than 50 tagged Sea Lampreys could have passed above the dam when no passage of tagged fish was observed. Results also showed that existing traps are in good locations because 83-96% of the population was available to existing traps. However, only 52-69% of Sea Lampreys available to traps were caught, suggesting that traps can be improved. In Chapter 2, I explored the current and possible future role of traps to control and assess Sea Lamprey in the St. Marys River, the connecting channel between lakes Superior and Huron. Exploitation rates (i.e., fractions of the adult Sea Lamprey population removed by traps) at two upstream locations were compared among three years and two points of entry to the system. Telemetry receivers throughout the drainage allowed trap performance (exploitation rate) to be partitioned into two components: proportion of migrating Sea Lampreys that visited traps (availability) and proportion of available Sea Lampreys that were caught by traps (local trap efficiency). Estimated exploitation rates were well below those needed to provide population control in the absence of lampricides. Local trap efficiency and availability estimates suggested that substantial increases in catch would require major changes to Sea Lamprey trapping systems, including improvements to existing traps, installation of new traps, or modifications to attract more Sea Lampreys toward and into traps. Lower-than-expected local trap efficiency estimates also suggested that traditional assessment methods underestimated abundance of spawning-phase Sea Lampreys in the St. Marys River and highlighted the need to evaluate the equal catchability assumption of mark-recapture models when a single trap is used for capture and recapture. In Chapter 3, I determined if migration behavior of adult Sea Lampreys in the St. Marys River was consistent with the current conceptual model of spawning migration. As expected, most adult Sea Lampreys made directed upstream movements until they encountered a barrier or entered a tributary. Results suggested that most Sea Lampreys spawned in the upper reaches of the St. Marys River near Sault St. Marie or in the three tributaries to the upper North Channel. The proportion of Sea Lampreys that presumably spawned at each location differed between release sites and among years due to differences in route selection probabilities at downstream bifurcations of the channel. The approaches used in this study may have broader applications, including evaluation of barriers and traps for other invasive species (e.g., Asian carp Hypophthalmichthys spp.) and fish passage structures for other diadromous fishes.
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