Bass virus continues to spread in Michigan waters: MI

Article Posted: May 24, 2004

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Bass virus continues to spread in Michigan waters

State fisheries officials today announced Largemouth Bass Virus continues to spread in southern Michigan lakes, and called upon anglers to help contain the disease and protect fish populations.

Largemouth Bass Virus is among more than 100 naturally-occurring viruses that affect fish. It is not known to infect humans, and infected fish are considered safe to eat. However, it is recommended that all fish should be thoroughly cooked as a precaution.

When LMBV was detected in the fall of 2000 in Lake George, on the Michigan-Indiana border, it was the first time the disease had ever been found in Michigan and was the furthest north LMBV had ever been found in the United States. The disease was first discovered in 1995, in South Carolina’s Santee-Cooper Reservoir, following a die-off of largemouth bass. Since then, it has been detected in wild fish from 17 states including Indiana, Illinois and


The Department of Natural Resources surveyed lakes in Southern Michigan for LMBV in 2002 and continued in 2003. Based on these and earlier data, the virus has been confirmed in 15 of 30 lakes examined. A list of surveyed lakes is available on the DNR web site,

Michigan DNR Fisheries Division and Michigan State University researchers continue to investigate LMBV and will monitor lakes throughout Michigan this summer.

Michigan DNR Fish Production Manager Gary Whelan said LMBV appears to infect other fish species, including smallmouth bass, bluegill, and crappies, but has caused mortality only to largemouth bass. The disease typically kills large adult fish and die-offs impact approximately 10 percent of these fish in a given lake.

There are few outward signs that a fish has the virus. Mortality occurs when fish are most stressed. Potential stressors include very hot weather, high angling pressure, and possibly aquatic weed or other treatments during very hot periods. Any measures that can be taken to minimize stress on these fish will reduce the impact of the disease and mortality.

“The DNR cannot eradicate this virus or treat affected wild fish populations,” Whelan said. “However, as we continue investigating this disease, we appreciate receiving reports of unusual fish mortalities.”

The DNR called on anglers who target largemouth bass to voluntarily help reduce angling stress on bass populations during warm weather, and reminded anglers and boaters to take the following steps to help prevent the spread of the virus:

* Clean boats, trailers, other equipment thoroughly between fishing trips to keep from transporting LMBV, as well as other undesirable pathogens and organisms, from one water body to another with special care to clean fishing equipment when you are done fishing known locations of the virus.

* Do not move fish or fish parts from one body of water to another, and do not release live bait into any water body.

* Handle bass as gently as possible if you intend to release them and release them as quickly as possible.

* Refrain from hauling the fish for long periods in live wells if you intend to release them.

* Minimize targeting of largemouth bass during the period from mid-July to mid-August, especially during exceptionally hot weather conditions.

* Report dead or dying adult largemouth bass fish to Michigan Department of Natural Resources Fisheries Division offices.

* Volunteer to help agencies collect bass for LMBV monitoring.

* Educate other anglers about LMBV.

The Michigan DNR will continue to communicate new information learned about the disease in Michigan. For more information, visit:

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