Little Effect on Fishing Expected from Hatchery Loss

By Evin Oneale, Idaho Department of Fish and Game Nearly 250,000 hatchery rainbow trout destined for stocking in Idaho waters this spring and summer have died from a disease outbreak at the Idaho Department of Fish and Game's Nampa Fish Hatchery. Despite this mortality, department staff members expect anglers to notice little difference in their fishing on trout-stocked waters this season. "We spread the deficit across the state such that most anglers should notice little change in the stocking rates of their favorite waters," Fish and Game resident hatcheries supervisor Tom Frew said. Nearly 250,000 rainbows perished as a result of an outbreak of "Ich" - Ichthyophthirius multifilis, a parasite common to waters across the globe, and one that is the scourge of tropical fish owners. Ich does not infect humans, nor does its presence represent any threat to human health. "However, it's important to remember that although we would certainly like to have those fish back, this fish loss represents less than 10 percent of the nearly 3 million catchable-sized rainbow trout produced by the department's hatchery system on a regular basis," Frew said. Several hatcheries, including Sawtooth, Nampa and Hagerman, have battled outbreaks of the parasite during the past three years. Severity of Ich is directly related to warmer water temperature, said Doug Burton, fish pathologist at Fish and Game's Eagle Fish Health Laboratory. Nampa and Hagerman have the warmest temperatures of all our rainbow trout hatcheries, but the Pahsimeroi Hatchery also has had problems with Ich, Burton said. Ich probably kills more freshwater fish of all kinds worldwide, than any other fish disease. Following the fish loss, department staff members prioritized the distribution of the remaining rainbows to maintain quality fishing for anglers. Like most department-owned fish hatcheries across the state, Nampa Hatchery is managed for maximum fish production. "Under these crowded conditions, a disease outbreak can spread rapidly through the population and have potential serious ramifications," Frew said. Once the outbreak was discovered, hatchery staff members moved quickly to bring it under control. But reducing the parasite's effect was difficult given the treatment available for food fish. "While the hobby aquarium industry has chemicals available to quickly and effectively control Ich, these could not be used to treat fish destined for human consumption," Frew said. For information about the loss of fish at the Nampa hatchery, contact Frew at Fish and Game headquarters in Boise, 208-334-3791. Evin Oneale is the regional conservation educator in Nampa.