Whirling Disease

Although Whirling Disease has a silly name, it has a deep negative impact on trout and salmon in Montana waters. The non-native species of parasite that causes the fish to "whirl" is introduced into the host fish by a native worm which attaches itself to the fish naturally. The parasite multiplies rapidly in the spinal cartilage of the salmon or trout and subsequently puts pressure on its organ of equilibrium. This pressure produces erratic swimming in fish, prohibiting them from successfully feeding or avoiding predators.

It is believed that Whirling Disease came from European brown trout, which are resistant to the parasite. The parasite can be spread after a fish dies from the disease, when the parasite can then make its way into another fish's spinal cartilage, making this a difficult disease to control. Thus it is important not to transfer fish from one body of water to another, to reduce the spread of the parasite spores.

Whirling Disease has had a devastating effect on Montana fisheries and recreational fishing. Efforts are being made to prevent the spread of the disease, but recreational fishers and outdoor lovers all need to contribute by not transporting fish or fish waste to other bodies of water, and other methods of prevention. I think this link link provides good basic information on stopping the spread of the disease.