Federal fishery researchers may have figured out a “template” for building a better springer.
Or at least rearing smolts that won’t fizzle out as minijacks.
Minijacks are male Chinook that are even smaller than jacks, which run to 24 inches, and while they may or may not go to sea, they’re reproductively viable.
In Oregon’s Hood River system, some years they’ve ended up representing as much as 40 percent of the output of state and tribal hatcheries, doing little for fisheries while also posing a threat to wild king genes.
So, the Northwest Fisheries Science Center was called in to take a crack at the problem.
According to a recent story posted on NWFSC’s website, over the course of a three-year study that began in 2010, eggs from one year-class of returning springers were reared at three different facilities, Carson National Fish Hatchery on the Wind, Parkdale Fish Facility on the Hood and Pelton Ladder on the Deschutes.
Then all were acclimated and released from Parkdale.
More than 40,000 smolts swam out with passive integrated transponders.
“In this way, any differences between the groups would be due to differences in the rearing environments alone—namely, the three hatcheries,” the story states.
The goal was to see which would achieve the highest smolt-to-adult return rate, or SAR, and thus fewest minijacks.
Pelton Ladder, which otherwise allows anadromous fish to climb the three miles between a pair of dams on the Deschutes near Madras.
“Although it’s artificial, it’s like a natural river system, with natural water temperatures and lots of foraging food and insects, instead of the managed temperatures and artificial food you see at many hatcheries,” Chris Brun, who coordinates the state-tribal Hood River Production Program.
Nicknamed the “wild fish template,” it suggests smolts raised this way “were consistently larger, better adapted to saltwater, and far less likely to become minijacks than those from the other hatcheries. They also returned in the greatest numbers as adults,” writes author Al Brown.
The researchers’ results have been published online and are set to go into print in Transactions of the American Fisheries Society.
Now, obviously hatchery operators may not have the coinage to build Pelton Ladders all over the Northwest to increase SAR, and perhaps there is some factor at play that makes the results peculiar to Columbia Gorge tribs, but it’s interesting nonetheless.