Spawning of Tule fall Chinook is underway at the Spring Creek National Fish Hatchery (NFH) in Underwood. The process began Sept. 16 with the return of the fish to the hatchery.
Last Friday, the Spring Creek hatchery was in full swing to spawn as many holding ponds as it could before the fish expired before laying, and fertilizing, their eggs.
“We’ve had sturgeon hanging around — see we still have a lot of fish coming in,” explained Mark Ahrens when peering down the fish latter at the hatchery. Spawning is in its third week and a mass of Tule fall Chinook still crowd the fish ladder entrance that leads to the holding ponds at the hatchery.
“They are returning home into our hatchery naturally, on their own,” Ahrens explained. “It’s like a chicken and egg thing: it’s a circle and this is the point in the circle where we’re getting the adults back.”
“Fish hone on their stream and water of origin, they’ll rear and develop in that home water source just like a river,” said Ahrens. For fish raised in the hatchery, the water that streams from the fish ladder is familiar and draws them back to the point of their origin.
“And when they get ready to migrate, and even before that, there’s imprinting going on just kind of like — I describe it to people that it’s much like us compared to the childhood and teen years,” Ahrens explained. “You get a sense of home and then you always have that, now the people that move too much don’t get that and that’s a problem with fish too. If you move them around too much and they don’t imprint right and they can have problems finding home.”
“But when you know, or grow up in an area that’s pretty stable, you get a good sense of home,” Ahrens explained that it’s similar with the fish, “but then at the same time when you hit the late teens that urge to leave home, puberty and on, just gets stronger and stronger. When fish are ready to go it’s a process called smoltification.”
The Smoltification process, also known as Parr-Smolt transformation, is a series of physiological changes where juvenile salmonid fish adapt from living in fresh water to living in seawater. Some changes include an altered body shape, increased silvery coloration, and some changes to the gill’s sodium-potassium pump.
The imprinted fish from the hatchery are also drawn to the ladder because the water running through it is a little cooler at 47 degrees compared to the Columbia’s, which is why the sturgeon have been hanging around.
“We’re going to have the ladder going probably through the first week of October, and then it will be slowing down dramatically,” Ahrens explained. Returning fish range from two to five years old, “…and the twos are almost always going to be early returning males; ‘Jacks’ are what we call them. And in a rare year you’ll get things like an early returning female and we’ll call them a ‘Jill,’ and they’re pretty rare. We get a few of those a year,” Ahrens noted.
Once the Chinook make it up the ladder they pass through an automatic fish counter, and Passive Integrated Transponder (PIT) tag detectors, which are three large PVC pipe squares, embedded into the entrance of the holding ponds. The PIT tags are the same type used to tag pets, in the fish they’re used to collect data and monitor the migratory habits of the fish that pass through the dams that comprise the Federal Columbia River Power System.
The automatic fish counter also relays the size of the fish that passes through the system by transmitting infrared light that captures a silhouette of the fish, so it can tell if it’s an adult. Those who work at the hatchery set the system’s preferences, what it classifies as ‘Jacks’ or older fish, and allows for an idea of what’s being held in the ponds before collecting.
The counter also allows for monitoring of how many fish occupy the 17 holding ponds near the spawning and information building. Monitoring the amount of fish being held allows for workers to switch pond collections at the right time, preventing the fish from becoming over crowded.
“We may get forty to fifty thousand fish in here this year, and we only need to run about eight thousand through the spawn room, and we want to get a good representative collection of parents throughout the run,” Ahrens explained, “we don’t want just all the front, we could easily do that and get spawning done in a week, but we need to spread it out. The run usually lasts about three weeks, so we try to get some early, a lot middle and some late.”
Once the fish make it to the ponds they’re corralled into the Spawning Room, where the Visitor Center is located. Fish are first squeezed on their lower abdomen to see if they’ll release eggs or milt, fish sperm, before being fed in to a machine that stuns and kills the fish. Once the fish has been led to the fatal strike it’s pushed down a chute to where it’s sorted by gender.
Female fish are sliced open, the eggs are collected in a bowl, and then the carcass is tossed on the floor and into a holding area for the harvested fish. The bowl of eggs is then fertilized by milt. To release the milt a worker squeezes the lower abdomen of a male fish, effectively spouting milt into the bowl of eggs.
If the fish are left in the ponds they won’t spawn, Ahrens says, since there’s no gravel but they will exhibit spawning behavior. “The egg readiness in fish is a process of ovulation and they hit a readiness, but for fish it’s a one way situation. When a female fish is ready to ovulate, its eggs are ready, the body’s degrading, and those eggs are going to start dropping out and they’ll get weaker and weaker, and pretty soon eggs will be getting [released], we’ll see them in the ponds and they’ll start rolling over and dying,” Ahrens explained.
That’s the ultimate indicator that a pond needs to be harvested, Ahrens says, their goal is to minimize mortality rates within the population that returned. Although there is always some die off that takes place. Some of harvested fish are given to the Discovery Center in The Dalles to feed their two resident eagles, while a number of surplus fish are given to the Northwest Harvest Food Bank Network.
After the eggs are fertilized they’re taken to a holding area where they sit and incubate. After about 90 days the hatchery will start to feed the fish. Then the process starts all over again.