** The title, authors, and abstract for this
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Determining routes
of adult sea lamprey escapement to the upper Cheboygan River and impacts on
adult abundance estimates with acoustic telemetry
Margaret Docker
2Hammond Bay
Biological Station, 11188 Ray Road, Millersburg, MI
3USFWS, Marquette Biological Station, 3090
Wright St., Marquette, MI 49855
March 2013
Abstract
The Cheboygan River is an important sea lamprey
producing tributary to Lake Huron. The
trap near its mouth captures more adult sea lampreys than any other in the Great
Lakes. Despite having an efficient trap and refurbished dam, the upper river
(upstream of lock and dam) remains infested with sea lampreys and has been
treated with lampricides on a 3-year cycle for nearly
50 years at an average treatment cost of $500,000 per treatment. Upstream escapement of sea lampreys through a
navigational lock near the dam has been hypothesized to be the source of
infestation in the upper river. Here, we
used telemetry data to estimate reach-specific probabilities of movement, including
trap capture and dam passage, for sea lampreys in the lower Cheboygan River, MI
by fitting the data to a Bayesian state-space model (BSSM). Movement probabilities through individual
river reaches were combined to estimate of the proportion of the population
present at each telemetry receiver and trap location, and further expanded by
the trap catch to estimate abundance at each location. Of an estimated 22 104 to 29 683 (95%
credibility interval) adult sea lampreys that entered the river, we estimated
that 46-61% were caught in the trap (i.e. exploitation). Although no tagged lampreys passed the above
the dam (0/148), the structure could not be considered a complete barrier to
sea lamprey migration because we estimated that 0-2% of the population, or 0 to
513 sea lamprey, passed upstream of the dam .
The BSSM provided a rigorous framework for inferring spatial dynamics
and allowed sampling variability to be considered when estimates were 0 or
1. Given our results, enhanced trapping
at existing sites in the Cheboygan River may have greater potential to increase
exploitation than adding traps at new locations because an estimated 82-95% of
the population reached the trap site, but only 51-68% of those were caught. Furthermore, given the low estimated rate of
escapement upstream of dam (fewer than 513 sea lampreys), yet consistent yearly
recruitment success, determining if the
upper river supports a sea lamprey population that completes its life cycle
without entering Lake Huron (landlocked) should be a priority before management
actions are taken at the lock and dam to ensure 100% sea lamprey blockage. If a landlocked population resides in the
upper river, plans to eradicate sea lampreys from the upper river should be
formulated prior to rebuilding the lock (a project currently being
explored). Otherwise, continued
lampricide treatments in the upper river would be necessary.