The U.S. Fish and Wildlife Service will treat portions of the Pere Marquette River later this month to control invasive sea lamprey larvae that threaten the Great Lakes fishery.
The treatments are scheduled between July 28 and Aug. 6 on the Pere Marquette River in Mason and Lake counties. The agency said the application dates are tentative and may change depending on weather or stream conditions.
Service personnel will apply lampricides to kill sea lamprey larvae that live burrowed in the stream bottom before they mature and migrate into Lake Michigan.
Sea lampreys are parasitic fish native to the Atlantic Ocean that entered the Great Lakes through shipping canals in the early 1900s. They attach to fish with a suction-cup mouth lined with sharp teeth and feed on body fluids. According to the U.S. Fish and Wildlife Service, a single sea lamprey can kill up to 40 pounds of fish during its parasitic stage.
Each spawning pair can produce up to 100,000 eggs. The larvae remain in tributary streams for several years before transforming into parasites that migrate to the Great Lakes.
The Fish and Wildlife Service said infested tributaries must be treated regularly with lampricides to control sea lamprey populations. Without treatment, the invasive species can cause significant damage to the Great Lakes fishery.
Before treatment begins, trained personnel will collect stream chemistry and discharge data and may conduct toxicity tests and streamflow studies. The agency said non-toxic dyes may be used during those studies, causing stream water to temporarily appear red or green.
During treatment, lampricides will be carefully metered into the river for about 12 hours. Concentrations will be continuously monitored at predetermined downstream locations to ensure the proper dosage is maintained. The applications are conducted by certified aquatic pesticide applicators.
More information about the Great Lakes sea lamprey control program is available at fws.gov/invasive-sea-lamprey.
Please Support Local News and Sports Coverage
Receive daily MCP and OCP news briefings along with email news alerts for $10 a month. Your contribution will help us to continue to provide you with free local news.
The payment can be paid monthly through PayPal: Click this link.
To sign up for an annual subscription, email editor@mediagroup31.com. In the subject line write: Subscription. Please supply your name, email address, mailing address, and phone number (indicate cell phone). We will not share your information with any outside sources.
For more than one email address in a household, the cost is $15 per month per email address.
We can send you an invoice for a yearly payment of $120, which you can conveniently pay online or by check. If you are interested in this method, please email editor@mediagroup31.com and we can sign you up. You can also mail a yearly check for $120 to Media Group 31, PO Box 21, Scottville, MI 49454 (please include your email address).
Payment must be made in advance prior to subscription activation.
We appreciate all our readers regardless of whether they choose to continue to access our service for free or with a monthly financial support.
_____
This story and original photography are copyrighted © 2026, all rights reserved by Media Group 31, LLC, PO Box 21, Scottville, MI 49454. No portion of this story or images may be reproduced in any way, including print or broadcast, without expressed written consent.
As the services of Media Group 31, LLC are news services, the information posted within the sites are archivable for public record and historical posterity. For this reason it is the policy and practice of this company to not delete postings. It is the editor’s discretion to update or edit a story when/if new information becomes available. This may be done by editing the posted story or posting a new “follow-up” story. Media Group 31, LLC or any of its agents have the right to make any changes to this policy. Refer to Use Policy for more information.
.png)
