Science & Environment

Pacific salmon seem to be getting smaller. Here’s what that might mean for the future

By Paul Marshall (OPB)
Jan. 30, 2023 1:55 p.m. Updated: Jan. 30, 2023 10:03 p.m.

The number of salmon returning to Bristol Bay Alaska from the Pacific Ocean last year was higher than it’s been in at least 20 years. But the fish themselves are smaller. And that seems to be true for other salmon across the region. Science and nature writer Miranda Weiss talked to scientists and fishermen about why the fish might be getting smaller, and what impacts that will have in the Pacific Northwest.


OPB’s Paul Marshall spoke with Weiss.

Paul Marshall: You went up to Bristol Bay, Alaska, which had a huge sockeye salmon run this year. Can you just describe what it looked like in the creeks and rivers for the summer?

Miranda Weiss: I had never seen anything like it. The creeks were full of fish. They were about half water, half fish. I was with ecologist Daniel Schindler hiking up these tiny little streams. We were wearing waders and wading boots and you’re just bumping into fish with every step. You have to be careful not just step on fish and slip on fish.

FILE - A brown bear walks to a sandbar to eat a salmon it had just caught at Brooks Falls in Katmai National Park and Preserve, Alaska. The number of salmon returning to nearby Bristol Bay, Alaska, from the Pacific Ocean last year was higher than it’s been in at least 20 years. But the fish themselves are smaller. And that seems to be true for other salmon across the region.

FILE - A brown bear walks to a sandbar to eat a salmon it had just caught at Brooks Falls in Katmai National Park and Preserve, Alaska. The number of salmon returning to nearby Bristol Bay, Alaska, from the Pacific Ocean last year was higher than it’s been in at least 20 years. But the fish themselves are smaller. And that seems to be true for other salmon across the region.

Mark Thiessen / AP

Marshall: So there may be more fish this year, but overall salmon seem to be getting smaller and returning to spawn younger. You did talk to researchers who found that the weight of Bristol Bay Sockeye has declined by 10% since the 1960s. And that seems to be true for other species. Can you first talk about what some of the consequences are of having smaller sized salmon?

Weiss: One of the main concerns is that with smaller fish you get a drop in reproductive potential. So we know that big fish begat more big fish. We also know that big fish, big female salmon contain more eggs and larger eggs than smaller fish.

For example, a really large chinook or king salmon female could have something like 17,000 eggs inside of her, whereas a small chinook might only have 3,000. So as the fish gets smaller, their reproductive ability drops. There’s other kind of ecological concerns that some of these researchers are thinking about.

Salmon are basically torpedoes of fertilizers in the stream environment. So we all know that they’re born in freshwater, they go out to sea and while they’re at sea‚ they’re gorging on all this sort of marine life: plankton, crustaceans, small fish. And then when they return to fresh water to spawn, they’re bringing what’s known as marine-derived nutrients. So all the nutrients from the food that they ate comes with them in their bodies as they go upstream. As the fish are getting smaller, the amount of those nutrients goes down

But then there’s the concerns for people because smaller fish can be a hit to a fisherman’s bottom line. Smaller fish are actually — I’ve talked to some seafood processors — they’re kind of a pain in the neck for processors. Productivity is measured in the number of fish that pass through the processing line in a minute and with smaller fish you just get fewer pounds per minute.

Marshall: There are a number of different reasons why the fish might be getting smaller, but everyone seems to agree that one of them is that there are just more fish out there competing with each other. What role do hatchery fish play in that?

Weiss: It’s so interesting to think about the fact that there are more salmon in the North Pacific now than there have been for a century. It’s a little bit counterintuitive because we’ve heard about failing salmon runs all over the place.

But the truth is that there are more fish right now than there have been and hatcheries are kind of adding on to this pile up of salmon.

In 2021, hatcheries in the Pacific dumped five billion salmon fry into the ocean. This is kind of an astounding number. There are more hatchery salmon than some types of wild salmon which really just means there are a lot of hungry mouths out there to feed.

Marshall: Are there any efforts to reduce the number of hatchery fish being released or to coordinate that somehow?

Weiss: Well, this is what’s really frustrating about this story. We’re not there yet. Right now, Pacific Rim nations are all kind of independently operating their hatcheries and dumping as many salmon fry into the ocean as they want.


No one is coordinating and many of these fish aren’t even marked in a way that researchers can tell where they’re from and we just don’t have that information.

There’s mounting evidence now that we just can’t keep dumping hatchery fish into the ocean without any repercussions. I’m at least encouraged that there’s increased awareness of this issue. It used to be the idea when these hatcheries were built was that the more fry you pumped into the ocean, the more fish would return. But what research is showing us is that the ocean’s pie is not infinite. Marine resources are limited.

Let’s say you put more hatchery fish in the ocean over here while you’re going to be taking away something else over there. There is an international organization that is really starting to address this issue. It’s called the North Pacific Anadromous Fish Commission. They’re essentially formed around the ban on high seas fishing when it became illegal to fish salmon on the high seas. There is some cooperation around that issue among Pacific countries, but we just haven’t yet seen cooperation on the hatchery issue.

Marshall: Climate change has this multilayered impact on the fish and its survival ability. How does that impact play out?

Weiss: Yeah, the way climate change is working on our oceans is complicated. Salmon are incredibly temperature sensitive. They need cold, clean water to survive. So one of the things that’s happening with climate change is that as waters warm, it’s basically shrinking fish habitat, some waterways are just no longer hospitable to salmon. The other thing that’s happening with climate change is that it’s shifting around marine food webs in ways that we don’t really even understand.

We’ve all heard about these massive sea bird die-offs in recent years. We’ve seen hundreds of thousands of seabirds just starve to death and something has messed with their food chain. In the Gulf of Alaska, the bottom dropped out of the Pacific cod population. We know that these complex and mysterious shifts are happening in marine food webs. And the other thing that’s happening with salmon and climate change is that it’s essentially making fish hungrier as the water warms.

It kind of ratchets up their metabolism so there might be the same amount or even less food to go around.

You have a lot of hungry fish and what we’re also seeing with climate change is that for salmon, there are some winners and there are some losers.

We’re seeing pink salmon be able to not just survive warmer temperatures, but even thrive in them and colonize new streams. We’re seeing them move farther north. Whereas other types of salmon aren’t doing as well when it gets warm.

Marshall: Though the returns may be bigger this year, there is an overall trend in decreasing salmon populations. And that decrease in salmon population has an impact on cultural traditions being passed down. Can you talk about that?

Weiss: It’s pretty amazing to witness the connection between salmon and people of Bristol Bay, especially the Indigenous people of Bristol Bay. I visited with a couple named Dee Dee and J.D. Bennis and every year their family comes together to harvest salmon and to process it.

They’re both of Indigenous descent and their families go back generations in the region — and their children and grandchildren come. They’re all kind of surrounded after they catch the fish on the beach with a setnet. They gather at the house around this old plywood fish cutting table and everybody is lending a hand and they’re passing on the tradition of how to cut king salmon filets, and how do you strip it and smoke it?

This is an anchor in their lives. It’s a joyous time. It’s what makes people feel connected to their place and to their ancestors and to the fish and to the resource.

Marshall: You did mention that you went snorkeling. Was it the researcher’s suggestion or was it your idea to go snorkeling?

Weiss: It was the researcher’s suggestion. It required a dry suit and a snorkel and mask. I waded upstream in a clear running creek that was a little bit deeper than my waist.

The water was cold and it felt kind of like ice water on my hands. I just crouched down into the flow of the current and I put my mask in the water. I’ve got my snorkel sticking out and I just kind of lowered myself in the water and let the flow of the stream take me down the creek.

At first, I only saw a few sockeye here and there but then all of a sudden I hit this mass of fish, it’s like a wall of fish that’s kind of waiting to run upstream. This creek wasn’t very deep, but these salmon are stacked like four fish deep, one over the other. Some of these males’ humps are so big, it looks like they’ve swallowed a frisbee. And you see these huge fish. Some of the salmon are starting to rot and their bodies are covered in this sort of lacy white fungus.

It was really so beautiful to be immersed in their world and just to be able to witness them and be part of this enormous and historic return of salmon last summer. How often do we really get the chance to immerse ourselves in a natural phenomenon like that, that has nothing to do with ourselves?

I just felt so lucky to be in the midst of that. It was really beautiful.

Support for Miranda Weiss’s story was provided by bioGraphic and the Food and Environment Reporting Network.