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Electrical Disruption Leads to Loss of Over 500,000 Trout at Hatchery

Giant Springs Fish Hatchery is located upstream and adjacent to the Rainbow Dam reservoir

By Beacon Staff

An unplanned electrical disruption at Rainbow Dam near Great Falls last week will result in the loss of more than 500,000 trout from the Giant Springs Fish Hatchery, state officials said.

At about 4 a.m. on May 12, the generating unit at Rainbow Dam tripped offline, according to Montana Fish, Wildlife and Parks, which operates the facility. The unplanned event caused a temporary loss of power at the dam and interrupted NorthWestern Energy’s ability to control and monitor the water elevation in the reservoir behind the dam. During a period of about 35 minutes, water levels in the reservoir increased by 18 inches, or 1.2 feet above full pool for the reservoir.

FWP staff found out about the event after arriving for work May 12. The river water had receded, but FWP’s measurements at the hatchery revealed the water had risen about one inch above the boards separating the raceways from the river.

Giant Springs Fish Hatchery is located upstream and adjacent to the Rainbow Dam reservoir. The Missouri River is known to be infected with whirling disease, a parasite that can be lethal to young trout. And though whirling disease is a concern, the unknown other pathogens that could be in the river water also made salvaging the trout problematic, according to FWP. With no way to confirm Missouri River water didn’t enter the raceways, FWP officials were forced to consider the more than 450,000 rainbow and 50,000 brook trout housed in the outside raceways infected, FWP officials said.

Most of the fish will be killed while about 20,000 will be put into the river immediately adjacent to the hatchery and 500 will go into the children’s fishing pond near the hatchery.

The inside raceways and tanks at the hatchery were not infected by river water.

“This is an extremely tough decision, but we felt the only course of action was to destroy the fish in the outside raceways,” said Eileen Ryce, FWP hatchery bureau chief and acting fisheries division administrator. “We take the health of our fisheries very seriously and our tolerance for risk to the public’s resource is very low.”

Ryce added, “More important than whirling disease is the overall exposure to the river water itself. This is a very unfortunate circumstance and the decision to euthanize these fish was not taken lightly. It affects our hatchery staff very deeply.”

Giant Springs, like other FWP hatcheries, is on a secure water system operating only on fish-free spring water. That ensures the water supply is free of fish pathogens.

“We don’t raise any trout on untreated river water because of the general disease concerns,” Ryce said.

Once the fish are destroyed and the raceways emptied, they’ll be disinfected and the hatchery will be back online.

FWP operates 12 hatcheries around the state and is also the licensing authority for Montana’s private fish hatcheries. It is agency policy not to transplant fish from infected hatcheries. Agency rules also prohibit private hatcheries that are under quarantine from planting fish in any water body.

The trout from Giant Springs were being raised for stocking efforts for reservoirs, lakes and ponds around Montana.  The planned fish stocking will continue with trout from other state hatcheries and donations from hatcheries operated by the U.S. Fish and Wildlife Service.

“We’re able to spread the burden of replacing these fish around to our other hatcheries and we’re also fortunate to have hatchery partners to help us find ways to make up for this loss,” Ryce said.  “We anticipate being able to fulfill most of our stocking plans for this year.”

NorthWestern Energy has a longstanding partnership with FWP and has worked closely with the agency since the unplanned event at Rainbow Dam. NorthWestern has agreed to share in the cost of disposing of the fish and the subsequent hatchery clean-up. The company will also work with FWP on the development of protective reservoir-level monitoring system for the hatchery.

NorthWestern is taking steps to improve the power feed system to Rainbow Dam, according to FWP. The company will develop a redundant reservoir-elevation monitoring system and establish a plan to provide early notification of future potential changes in water levels in the reservoir that could affect hatchery operations.

Rainbow Dam and its other Montana hydroelectric facilities operate under a Federal Energy Regulatory Commission (FERC) license and NorthWestern has notified FERC of the event. Along with the notification, NorthWestern outlined to FERC the corrective actions it will take to prevent reoccurrence.

“NorthWestern takes its hydro operations compliance responsibilities very seriously and is working to develop corrective actions to prevent reoccurrence of this Rainbow full-pool exceedance,” said Jon Jourdonnais, leader of hydropower license compliance at NorthWestern Energy. “NorthWestern also considers Montana Fish, Wildlife and Parks to be an effective and valued  state-wide partner on many mutually managed public river resource and recreational issues.”