A disease outbreak killed roughly 75 percent of the summer steelhead smolts being reared at a Hanford Reach hatchery, a blow to a fishery and program that have had a tough few years.
WDFW reports that it was able to release somewhere around 50,000 of the juvenile fish from Ringold Springs into the cooler waters of the Columbia River to give them “a fighting chance,” but couldn’t find backup stock for the other 150,000 or so that were lost.
“We actively tried to find replacements, but it was too late in the rearing cycle,” said Brian Lyon, the state hatchery complex manager, this morning. “We would’ve replaced them if we could have, believe me.”
The news was first reported on WDFW’s Medium blog Jan. 13.
Crews first detected what is known as “Ich,” or Ichthyophthirius multifilis, in December and treated a 2.5-acre pond used to rear nearly 200,000 steelhead, but were unable to stop the outbreak, so after a week and a half released the survivors.
The disease, which is spread by a parasite and affects the gills and skin of fish, was also found in other ponds at Ringold that hold coho and rainbow trout, but treatments were successful and few of those fish were lost, according to WDFW.
It wasn’t clear how the steelhead came to be infected.
Ich exists in the Columbia and could have been carried into hatchery waters by predators — Lyon says that if a bird ate an infected fish then pooped as it flew over the ponds, it could transmit the disease that way.
Otters might have also been to blame. WDFW says there are deterrents at the hatchery but sometimes hungry critters can worm their way in.
The last Ich outbreak at Ringold was 10 years ago, WDFW reported, but the 60-degree spring waters that feed the ponds are ideal growing conditions for the disease, according to Lyon.
Releasing the surviving steelhead into the cooler waters of the Columbia should have given them a “better” chance of survival, his agency reported. In December the big river was running in the upper 40s and it is now in the upper 30s below Priest Rapids Dam, at the head of the Hanford Reach.
Lyon said the smolts were about a year old at the time of the outbreak but unfortunately no surplus fish were available at other hatcheries, including Wells further up the Columbia.
The steelhead were being reared for return in 2021’s lower Hanford Reach fishery. Angling for summer-runs there has been poor in recent seasons, with the waters closed to retention this past fall and shut down early in 2018 to try and ensure that broodstock goals were reached.
Ich was blamed for the loss of about 6,100 wild and hatchery adult Chinook in Willapa Basin streams in 2015, while this past fall another naturally occurring disease, cryptobia, hit fall kings in rivers on Oregon’s North Coast.
WDFW said it is reviewing the Ich outbreak at Ringold “to determine whether measures can be put in place to prevent a re-occurrence.”