How One Hatchery Moved 160,000 Baby Salmon
A little too true to its name, Warm Springs National Fish Hatchery got toasty this July—putting all its cute baby salmon at high risk. Already witnessing August temperatures at the end of June, Warm Springs was forced to take action. After contemplating impossibly expensive AC systems (picture a $200,000 monthly bill), the hatchery decided it was time for a change of venue: to Little White Salmon Hatchery in the Columbia River Gorge.
We asked Mark Ahrens, the Pacific Region’s Chief of Fisheries Operations, to tell us how they did it, why warm temperatures are dangerous for salmon, and whether this problem is likely to continue.
What does moving over 160,000 salmon look like?
It’s a little different for juvenile fish versus larger fish. Getting small, fingerling–sized fish into a truck requires a different technique. We can use gear called a fish pump. It’s a very gentle suction device that doesn’t require blades. So you can elevate them about fifteen feet in the air above a tank truck. We run ‘em up to a dewatering tower, they go sliding over this slightly–angled screen where the water falls down through a drain tube, but the fish slide off the slippery end into the truck so we’re not overfilling that truck with water.
We have to run the adult fish up by hand since they’re larger. We’re not taking the water to the truck—the truck’s already full and ready for ‘em. Adults are pretty resilient, all these fish are: they can be out of water, and as long as their gills are wet, they’re happy. When we take them to the truck, it’s as fast as we can without harming them—and the trucks are rigged with oxygen and aeration pumps: they have a little contained aquarium for the road.
Did they all survive?
Any that weren’t already compromised: there were some parasites and bacterial issues we were treating for, and those fish were not doing well at Warm Springs. So we moved them urgently and early enough to save as many as we could, because things were only gonna get worse. Taking them to colder water was the only remedy for this situation. We kind of ran out of treatment options because the water was getting warmer, and flows continued to drop, and there was no hope for significant improvement because the snow’s packed so low.
These parasites and bacteria, are they caused by the warmth?
No, they’re exacerbated by it. It becomes an optimal condition when you get these warm environments, bacteria, viruses and parasites all thrive. Optimal temperatures for salmon are in the 40-50 degree range. And when you start going above 55 into 60, 65, 70, 75... it just continues to get worse. And that’s what we’re seeing in the main stem Columbia. To top it all off, when the water gets warmer, the dissolved oxygen content of water drops as well. The stress is higher when they have a harder time breathing. Their metabolic rate is higher, food can become less available, there’s a reduced availability of space, because of the levels of rives, and there are less places to hide. Predators have a much easier time finding them. There are so many challenging variables that become amplified when we get into these high temperatures.
Are you planning on moving them back?
Yes, probably when temperatures reduce and workload does in our local Columbia Gorge area—we’re thinking a good window is that early October period, if the temperatures are acceptable. We’ll get them back to Warm Springs and they’ll do just fine until next spring’s release.
How is this affecting the temporary fishing restriction in Oregon?
They’re doing it in Washington as well. The heat has slowed it all down quite a bit. The fish just aren’t biting as well. Fishing is more limited in the afternoon as temperatures are rising in tributaries and the main stem. They decided to restrict fishing to reduce stress and the risk of extra mortality on already strained fish.
Do you see this as an on going problem? I can’t imagine that it’ll be cooling down in future years...
I think we’ve seen a trend take us to this point of warmer waters. Over my 12 years, I’ve seen a trend towards milder winters. Spring Creek is very much an aquarium-like system with a lot of solar input, and it warms up quite a bit there; that has caused us some issues with health even as we get into the mid-50 degree range. Hatcheries were built with the assumption that we had normal environmental conditions to base some expectations on, and those assumptions are now needing to evolve. I think we all have been aware there’s potential for different weather down the road and we’re seeing it play out right now.
Are the affected fish mending in Columbia River Gorge?
Oh yeah. Getting to Little White Salmon where the water is 50 degrees and lower, it was an ideal switch. On the other end, mortality reduced 10 to 20 times less. The fish are much happier over there.