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Determine the origin of sea lampreys in the Upper Cheboygan River
N. S. Johnson1, A. Lochet2, S. Miehls1, M. Twohey3
1 USGS, Hammond Bay Biological Station, 11188 Ray Road, Millersburg, MI, 49759
2 Private contractor, 313 East Willow Street, Apt 319, Syracuse, NY 13203
3 USFWS, Marquette Biological Station, 3090 Wright Street, Marquette MI 49855.
The Cheboygan River, MI, is an important sea lamprey producing tributary to Lake Huron. The upper reaches of the river system are separated from the lower river by a lock and dam system located 2.5 km from Lake Huron. The sea lamprey trap near the tailrace of the dam captures more adult sea lampreys than any other trap in the Great Lakes. Despite having a refurbished trap and renovated dam the upper river remains infested with larval sea lampreys and must be treated with lampricides about every three years at a cost averaging $500,000. Upstream escapement of adult sea lampreys through a navigational lock near the dam (the key component of Michiganís Inland Waterway) has been hypothesized to be the source of infestation in the upper river (H1). This lock requires significant refurbishment or replacement in the near future. An alternative hypothesis (H2) is that the upper Cheboygan River supports a population of sea lamprey that completes its life cycle without entering Lake Huron (landlocked) because the upper watershed has two large deep lakes containing salmonid populations. To provide evidence for or against the existence of a landlocked population to inform lock refurbishment plans, we captured adult sea lamprey from the upper Cheboygan River using fyke nets to determine run timing and obtain morphology and statolith microchemistry data. Adult sea lamprey abundance in the upper river was also estimated by weekly fin clipping (marking) male sea lampreys captured in the lower river (Lake Huron source) and releasing them in the upper river (Schaefer method). Collective results provide evidence that a small landlocked population of adult sea lampreys inhabited the upper Cheboygan River during 2013 and that escapement through the lock was minimal. Only 4 adult sea lampreys were captured in the upper Cheboygan River yielding an adult sea lamprey abundance estimate of 36; although the precision of this estimate was low due to low recapture rates of marked sea lampreys (coefficient of variation = 36). An unmarked adult sea lamprey was captured in the upper river prior to lock operation and zero unmarked sea lampreys were captured in June when lock activity was greatest. Despite the small sample size of unmarked sea lampreys (n=4), we found that unmarked sea lampreys captured in the upper Cheboygan River were significantly smaller than recaptured, marked sea lampreys from the lower Cheboygan River. Furthermore, statoliths from unmarked sea lampreys had significantly lowerRb concentrations and higher Sr concentrations than statoliths from marked sea lampreys. To inform lock refurbishment, additional years of research in the upper Cheboygan River will be conducted to substantiate the existence and viability of the putative landlocked population (Funds granted from USGS). Deciding whether the Great Lakes Fishery Commission will replace a sea lamprey barrier is an economic decision driven by the expected life and efficiency of the new structure, lampricide treatment frequency, and treatment cost. The decision to invest in Cheboygan lock modifications is more complicated because the GLFC must also consider the cost and uncertainty of eradicating the putative landlocked population. In light of these challenges, the upper Cheboygan River could offer a unique experimental system by which to test alternative control techniques and sea lamprey eradication strategies, of which if successful, could be expanded to the Great Lakes.