TRAIL, Ore. — Dave Pease always gets a bit nervous when he sends a few hundred thousand of his charges to freedom in a not-so-ceremonious way.
Two Cole Rivers Hatchery technicians force the spring chinook salmon smolts out of the concrete pen that has been their nursery for the past six months. They are swept down a dark, grate-covered canal and then spit out of a pipe and into the Rogue River for a harrowing 157-mile venture to the sea.
“Always a little nervous when we’re kicking them out of the nest,” says Pease, the hatchery’s manager. “You spend all this time raising them, you don’t want anything to go wrong.”
But something has gone wrong with Cole Rivers’ spring chinook. They are not returning as adults in large enough numbers to satisfy sport anglers forced to angle largely for wild spring chinook that they must release during most of the Rogue’s famed spring chinook run.
But the fish Pease and his technicians sent down the Rogue Tuesday are more than just one batch of the 1.7 million spring chinook smolts kicked loose annually from Cole Rivers.
They are part of a series of short- and long-term experiments meant to hone a new smolt-release strategy that will be designed to get more hatchery spring chinook to survive their two or three years in the ocean and return to fill coolers, barbecues and smokers the way past generations of hatchery fish have.
On the table are such things as truck-rides to salt water as well as tracking myriad variables such as ocean temperatures, fall coast winds and even September rainstorms to gauge whether any of these factors play a role in smolt survival once they join wild chinook smolts in the ocean.
“People are upset that we aren’t getting enough hatchery fish back, and we get that,” says Pete Samarin, an Oregon Department of Fish and Wildlife biologist heading up the experiments.
“The goal here is to maximize the survival of hatchery fish as much as we can,” Samarin says. “We can’t help them survive in the ocean, but if we can time their entry right, we feel we’ll be giving them the best chance for survival.”
In the wild, spring chinook spawn in the fall and their progeny hatch in late winter, fending for themselves until mid to late summer when they work their way downstream and enter the ocean at around five inches long.
Hatchery chinook are spawned in buckets, hatched in plastic trays and reared in concrete ponds before they are flushed into the Rogue, where they make a beeline for the sea.
“They’re going to the ocean, and they’re not eating their way to the ocean like wild fish do,” Samarin says.
To test that, hatchery technicians are using coded-wire tags and clipped fins on about 62,000 smolts to note their sub-group. Half of them will be released at Cole Rivers and the other half were trucked in late August to Gold Beach for release directly into the estuary.
When they return to the hatchery as adults, their relative survival rates will be logged and compared.
“We’re expecting them to return to the hatchery at the same rate,” Samarin says. “We don’t expect them to imprint on the estuary, return and swim in circles there.”
A separate release strategy looks to imitate the life-history of some of the spring chinook that were born and reared in the icy cold waters now blocked from the ocean by Lost Creek dam, Samarin says.
Some of those chinook stuck around a full year before heading to sea as smolts. To recreate that, Cole Rivers has raised about 91,000 smolts a full year and released them into the Rogue at Gold Hill last March.
Surviving adults that return to Cole Rivers in future years will be compared against return rates from other subsets to gauge their relative success.
The remaining 1.57 million spring chinook are released August through October directly from the hatchery, such as those kicked loose Tuesday.
Plans are to juggle releases and log various environmental conditions when they were released. Those conditions include such things as ocean water temperatures and wind velocities that help boost the near-shore food chain as the smolts hit the ocean.
Other possibilities include keeping track of fall rains to see if fish released before or after a September storm survived at different rates.
If smolts released after the rains survive better than smolts released before them, then Pease’s crew could be on notice to empty that concrete nest accordingly.
“There are a lot of pieces to the puzzle, and it takes time to put it all together,” Samarin says.
Information from: Mail Tribune, http://www.mailtribune.com/
