Fish parasite shows up in Wisconsin

A parasite of salmon and trout, shown here in a microscopic photo, has been detected in Wisconsin. (DNR photo)

Anglers and fishermen are being cautioned by the Department of Natural Resources (DNR) to properly clean their catch and gear. Recently in Elton Creek, which flows through Langlade County, a parasite was discovered which has not been previously detected in Wisconsin. The parasite, Myxobolus cerebralis, is a microscopic organism which damages cartilage and nerve tissue in trout and salmon. It’s also been known to cause whirling disease, characterized by a “whirling” swimming behavior triggered within afflicted fish.

“It’s unknown how Myxobolus cerebralis will impact our local trout populations at this time,” said Justine Hasz, DNR Fisheries Management Bureau Director. “In some states where the parasite has been found, trout and salmon have developed whirling disease, which has negatively impacted their local populations. However, other states with the parasite have seen no evidence of fish with whirling disease nor have they seen their trout and salmon populations impacted.”

The DNR said in a press release that while no fish has been observed with symptoms of disease caused by the parasite, it is implementing a surveillance program. By expanding testing and observation, the state agency will determine whether other trout populations are affected by the new arrival.

Elton Creek is a Class 1 trout stream, described on the DNR’s website as “high-quality trout waters that have sufficient natural reproduction to sustain populations of wild trout, at or near capacity.” In such streams, no hatchery or stocking of fish is needed, and just 40% of trout stream mileage in Wisconsin are of such quality.

The DNR is encouraging anglers and fishermen to report any fish exhibiting symptoms of the parasite or whirling disease. Those may include blackened tails, deformities, or the fish swimming in circles. However, it’s important to keep in mind that whirling disease isn’t the only ailment which may cause those symptoms. The parasite which causes the disease is also only capable of infecting salmon and trout, particularly rainbow and brook trout. Other species of fish, as well as humans, and household pets, are not in danger.

That said, the DNR also notes that the parasite is nearly impossible to eradicate once it appears in an ecosystem. Cleaning and disinfecting gear after fishing is critical, the state agency reported in a  press release. Wearing rubber-bottomed boots or waders is recommended, and all aquatic vegetation and dirt must be removed, as it might contain the parasite. Everything from boots to boats should be completely dried before being used again. The DNR also warns against disposing of fish tissue or by-products into bodies of water to further limit the parasite’s spread.

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