Parasitic Mold Showing Up On Multiple AK North Slope Fish Species For First Time Ever

The town of Nuiqsut, Alaska, sits on the Kuukpik (Colville) River near the Beaufort Sea. Residents harvest seals and ptarmigan, goose eggs and caribou. But nearly one-third of their subsistence diet comes from fish. The largest catches come during the fall, when Arctic cisco (qaaktaq), broad whitefish (aanaakłiq), and other species move from the ocean into the fresh water to feed and spawn. Local fishers set gill nets in the river or under the ice, hauling in tens of thousands of kilograms of fish annually for the village of about 425 mostly Iñupiat residents. But in recent years, an unusual illness has affected their catch.

In early October 2013, local fishers Eli Nukapigak and Edward Nukapigak Jr. alerted wildlife officials to the discovery of “sick fish” in their nets near Nuiqsut. The aanaakłiq had fuzzy grayish-white patches on their bodies, fins, and heads. Cottony masses almost covered the eyes of some fish. None of the fishers in the community recalled seeing this condition before. The impact on the community was immediate: some stopped fishing for aanaakłiq, while others refused to eat even uninfected fish that had been caught in the same net with infected fish. Some moved away from traditional fishing locations and others pulled up their nets for the season.

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The week after the Nukapigaks’ report, the state fish pathology laboratory identified the growth as a Saprolegnia-like mold. Although the condition is unsightly, the lab considers infected fish safe to eat. “I’m sure nobody ate them,” says Todd Sformo, a wildlife biologist for the North Slope Borough, who investigated the incident and reported the findings in a recent study. “I’m not real squeamish, but once you see that, you don’t want to eat it.” DNA analysis identified the mold as Saprolegnia parasitica, which is known for causing savage infections in fish eggs and juvenile fish in hatcheries around the world. Often associated with environmental stressors, it kills an estimated 10 percent of hatchery salmon globally.

Although Saprolegnia parasitica is widespread in fresh water in mild and warm climates, it is rarely seen in Alaska. Sformo says this is the first confirmed time it has been seen on the North Slope. No one knows yet why the infection has suddenly taken hold. “That’s the million-dollar question,” says Paul de la Bastide, a mycologist at the University of Victoria in British Columbia. The river’s water quality—concentrations of metals, diesel, and organics, for example—doesn’t seem to have changed in 20 years, though longer-term data is lacking, says Sformo. There are no water temperature records, but residents say that warmer temperatures and an earlier spring thaw now erode riverbanks and lead to murkier water.

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https://www.hakaimagazine.com/news/fuzzy-fish/