Advisor: Brian Sloss
Estimating the genetic heritage of lake trout produced at Lake Michigan’s mid-lake reef complex
Lake trout (Salvelinus namaycush) were extirpated from Lake Michigan in the 1950s. Following this extirpation, stocking efforts were begun in 1965 with the goal of restoring a self-sustaining population of lake trout that is capable of withstanding commercial harvest. Currently, four lake trout hatchery strains are used for stocking the mid-lake reef complex area of Lake Michigan, with the idea being that at least one of these strains may be better adapted to survival in contemporary Lake Michigan conditions than the other strains. The mid-lake reef complex is an area consisting of four deep-water reefs (deeper than 80 meters) and is considered to be the best lake trout spawning habitat in Lake Michigan. After over 40 years of stocking, however, Lake Michigan’s lake trout populations are still not self-sustaining. A small amount of natural reproduction has been recorded, but this reproduction is not enough to constitute true success. If fishery managers and biologists are able to determine which of the four hatchery strains are successfully reproducing, stocking efforts could be focused on those successful strains.
With
genetic approaches, biologists are able to determine the hatchery strain
of origin of pure strain lake trout by using seven microsatellite
genetic markers adapted to lake trout from other salmonid species.
However, under natural conditions multiple strain spawning aggregates
are expected to form, which likely result in interstrain hybrid
offspring. The computer algorithms that are used to identify pure strain
lake trout based on the microsatellite genetic data are untested in the
identification of interstrain hybrid lake trout, and will need to be
tested under these conditions to determine their performance
capabilities prior to use for making lake trout restoration and
management decisions. I will test the performance capabilities of six
computer algorithms used for individual population assignment or
admixture analysis by creating a simulated population of first
generation hybrids (F1), second generation hybrids (F2), and backcross
hybrids from the four hatchery strains currently used for stocking. By
using individuals with a known source, I will be able to test the
precision and accuracy of the algorithms for identifying hybrid origin
lake trout. The algorithm(s) found to have the highest performance
capabilities will be used to identify the strain(s) of origin of lake
trout eggs and fry collected from the mid-lake reef complex of Lake
Michigan. If the algorithms are found to have poor performance
capabilities with the seven currently used microsatellites, I will work
to develop lake trout specific microsatellite markers that can be used
in addition to the seven markers currently in use. These new markers
will provide for additional ways to distinguish between the multiple
hatchery strains and for identification of interstrain hybrid offspring,
thereby providing fishery managers and biologists with the information
necessary to focus stocking efforts towards those lake trout strains
with proven spawning success in the contemporary Lake Michigan
ecosystem. Stocking these successfully spawning strains could lead to an
increase in naturally produced lake trout which eventually could lead to
a self-sustaining lake trout population in Lake Michigan.