**ABSTRACT NOT
FOR CITATION WITHOUT AUTHOR PERMISSION. The title, authors, and abstract
for this completion report are provided below.
For a copy of the full completion report, please contact the author via e-mail
at ureinhard@emich.edu. Questions? Contact the GLFC via email at frp@glfc.org or via telephone at 734-662-3209.**
FIELD COMPARISON OF
EEL-LADDER-STYLE AND TRADITIONAL SEA LAMPREY TRAPS
April 2014
ABSTRACT:
We tested if an eel-ladder-style trap (ELST) can be
used to trap adult sea lampreys, Petromyzon marinus, in routine trapping operations over two
spawning seasons. The ELST consisted of a wetted inclined ramp with vertical
pegs arranged in a regular pattern, leading to a vertical drop into a
collection box. We assessed catch rate
of ELST compared to traditional funnel traps with “fingers” at three locations,
the St. Marys River (2012 only), Cheboygan River, and
Ocqueoc River. At the Brule River in 2013, we tested
if the ELST ccould be used in sorting adult sea
lampreys from fin-fish. In addition, at the Cheboygan and Ocqueoc
rivers we observed lamprey behavior on the ELST using PIT tags and video and
tested for any trap bias using a differential marking scheme. We found sea
lamprey capture rates of ELSTs to be lower than that of the traditional funnel
traps at the Ocqueoc River, but higher at the
Cheboygan River. However, unlike the funnel trap, the ELST did not trap any
fin-fish. Using an ELST at the St Marys River did not
improve the overall capture rate at the test locations. At the Brule River, the
spawning run was small, but all sea lampreys entered the ELST, effectively
sorting them from hundreds of fin-fish. ELSTs were 100% effective at retaining
captured sea lampreys, while the funnel trap at the Cheboygan River allowed considerable
escapement. Fish caught in the ELST, marked and released showed trap happiness,
i.e. returned to the ELST in preference over the paired funnel trap. The
success rate of fish attempting to enter the ELSTs varied between years and
locations between 16% to 79% probability of finishing an attempt. Particularly
in the Ocqueoc River, many climbing attempts were
aborted early in the climbing phase. The visual impression was that most aborted
attempts were voluntary, i.e. not due to fatigue. No physical differences
between lampreys retrieved from the ELST and paired funnel trap were found at
the Ocqueoc location, while at the Cheboygan location,
smaller males, more females and females with lower GSI were found in the ELST. Due
to their perfect selectivity and retention, eel-ladder style traps can become a
valuable tool for sea lamprey management. With further research on attraction
flow and ELST ramp substrate, the entry and success rate of the ELST can be
increased to match or surpass the catch rate of the traditional funnel traps.