Department of Natural Resources
Piscirickettsia - A New Pathogen in Lake St. Clair Muskies - A Fact Sheet of our Current Knowledge
Resource Background: The muskellunge fishery of Lake St. Clair has a reputation among muskie anglers for unusually high catch rates. The fishery draws anglers from the local area as well as from across the continent. Numerous charter fishing businesses specialize in muskie trips. Countless individual anglers fish exclusively for muskellunge while the season is open. A large Detroit area angling club is dedicated to the sport of muskie fishing. Many Lake St. Clair muskellunge anglers espouse a strict catch-and-release ethic. The Lake St. Clair muskellunge fishery is completely self-sustaining, thus any threat to the continued successful recruitment of muskellunge in the lake is a serious concern for fisheries managers.
Pathogen Detection in Lake St. Clair: : In May of 2002, the Michigan Department of Natural Resources (MDNR) collected several muskellunge exhibiting unusual red skin rashes from the Anchor Bay area of Lake St. Clair. The rounded rashes reached up to one inch in diameter (Figure 1). Laboratory analysis at Michigan State University by Dr. Mohamed Faisal, revealed the association of these lesions with a Gram-negative, curved, intracellular bacterium that occurred as rings or curved rods (Figure 2). Based on their shape and culture characteristics, the organism was determined to be a Piscirickettsia-like organism.
Pathogen Impacts in Lake St. Clair: While the Piscirickettsia-like organism has been found in Lake St. Clair, MDNR surveys and reports by fishermen have not indicated negative impacts in the muskellunge fishery.
Fisheries Division Action Plan: The discovery of this infection in Lake St. Clair muskellunge has raised the following questions:
In response to public concerns, the MDNR has assembled a team of fishery biologists, managers, and specialized veterinarians to investigate this case and to find answers to the above-mentioned questions. This summer, Fisheries Division with cooperating muskie anglers' assistance will be surveying Lake St. Clair to better describe the distribution and prevalence of this pathogen in muskies. Muskie anglers wishing to assist in the survey effort and anglers that catch a muskie in Lake St. Clair bearing red sores similar to those shown above are asked to report their observation to the Mt. Clemens Fisheries Research Station using the contact information below.
For more information on Piscirickettsia in Lake St. Clair's muskellunge:
Michael V. Thomas, Fisheries Research Biologist
Mount Clemens Fisheries Research Station
Figure 1. A Lake St. Clair muskellunge bearing the red lesions or sores characteristic of the Piscirickettsia infection.
Figure 2. Electron microscopy image of the Piscirickettsia sp. bacterium isolated from Lake St. Clair muskellunge in 2002.