**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NOT FOR CITATION WITHOUT AUTHOR PERMISSION.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 njohnson@usgs.gov. Questions? Contact the GLFC via email
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2U.S. Geological Survey,
Great Lakes Science Center, Hammond Bay Biological Station, 11188 Ray Road,
Millersburg, MI 49759
3U.S. Fish and Wildlife
Service, 3090 Wright Street, Marquette, MI 49855
4USGS, Upper Midwest
Environmental Sciences Center, 2630 Fanta Reed Road, La Crosse, WI, 54603, cmerkes@usgs.govsheries
and Oceans Canada, 1219 Queen Street East, Sault Ste. Marie, ON P6A 2E5
December 2020
ABSTRACT:
Sea lamprey (Petromyzon
marinus) are invasive in the Laurentian Great
Lakes, parasitize large-bodied fishes, and therefore are the focus of an
international control program. However, damage
caused by sea lamprey to modern day fish stocks remains uncertain because diet analysis
of juvenile sea lamprey has been challenging; they feed on blood and are
difficult to randomly sample in the lakes.
Here, both challenges were addressed in a proof of concept study showing
that DNA metabarcoding of fecal material can be used
to identify the diet of actively feeding juvenile sea lamprey, and can also be used to determine what adult sea lamprey
captured in streams fed on while parasitizing fish. Fecal samples from juvenile sea lamprey that
were feeding on lake trout in northern Lake Huron overwhelmingly contained lake
trout (Salvelinus namaycush)
DNA (90%), while smaller percentages contained lake whitefish (Coregonus clupeaformis;
5%) and longnose sucker (Catostomus catostomus;
5%) DNA. Fecal samples from adult sea
lamprey captured from a tributary to northern Lake Huron overwhelmingly
contained longnose and white sucker DNA (Catostomus spp.; 80%), while a smaller percentage contained
lake trout DNA (10%). Diet composition of
adult sea lamprey sampled in Black Mallard Creek was more diverse than juvenile
diet composition. DNA metabarcoding suggests that Catostomus spp. may be an
important host fish in northern Lake Huron for sea lamprey prior to spawning. Future research could investigate how diet
varies across years and lakes and the prevalence and sources of DNA
contamination. Adding diet analysis to
annual trapping assessments of adult sea abundance may be practical for
identifying populations of sea lamprey that feed on highly valued fishes.