Blistered Bighorn Trout
By Matt Schauer

Posted: June 22, 2012

Some fish below the Yellowtail Dam Afterbay (pictured above) are pretty creepy looking this spring – pocked with blisters on their fins, head and mouth. Incidents of gas bubble trauma seem to either be more prevalent or at least more visible this spring, possibly because of a few different factors.

Gas bubble trauma is caused by nitrogen supersaturation in the water. It happens as water captures air when it plunges over dam faces or even waterfalls. The Bureau of Reclamation is at a loss to explain why the problem seems to be cropping up this year, although work is being done on the Afterbay Dam. The Afterbay regulates the flow of water into the Bighorn River below Yellowtail Dam.

Fish, Wildlife and Parks biologists believe that the problem is showing up this year because fish may have been exposed to supersaturated water several times over the past year, making it more prevalent. It may also be more visible because the water is lower so that fish that have been killed by GBT are easier to see.

The problem is concentrated on the upper end of the popular trout stream. Farther downstream, the presence of GBT seems to diminish. FWP assured anglers that eating fish that are suffering from GBT is not a problem.

Here is the link to the story: http://billingsgazette.com/lifestyles/recreation/fish-blistered-by-high-nitrogen-levels-in-bighorn-river/article_7a546ca7-46b6-5907-a4fc-64ab42ad3745.html

Listen to Brett French, Billings Gazette Outdoor Editor, live tomorrow morning on the Montana Outdoor Radio Show, from 6:00 to 8:00 a.m.  The Captain will be broadcasting live from the water on Canyon Ferry Reservoir at the Canyon Ferry Walleye Festival.