Three-spined sticklebacks are small, green and brown fish with spines that run along their backs. In Lake Iliamna in the Bristol Bay region, three-spined sticklebacks eat the same plankton that juvenile sockeye salmon rely on to grow.
This year, researchers from the University of Alaska Fairbanks plan to run some experiments there to better understand sockeye’s small, spiky competition, and if warming waters might give them a competitive advantage.
Elena Eberhardt is a masters student studying fisheries at the University of Alaska, Fairbanks. Three years ago, Eberhardt was working as a research technician at Lake Iliamna for the summer.
Late at night, she says she would go out into the lake to do something called surface trawls.
“ You go out at night because it has to be dark out because the fish kind of come up to the surface,” Eberhardt said. “You know Alaskan summers, it's kind of a pain to figure out when it's actually going to be dark out.”
Eberhardt says after 10 p.m., the researchers would take a boat out, stick a net in the water, and then count juvenile sockeye salmon and whatever else they ended up catching.
One night, Eberhardt was out on the lake with her advisor at the University of Alaska Fairbanks.
“He was remarking like, ‘Wow, you know, we have a pretty high proportion of sockeye catch this year… Some years we've had tons and tons of three-spined stickleback,’” Eberhardt said.
Three-spined sticklebacks can live in both fresh and salt waters across the world – including in Bristol Bay. Eberhardt says they’re good at adapting to change.
Curry Cunningham is a Professor of Fisheries at University of Alaska Fairbanks, and Eberhardt’s advisor.
“[Three-spined sticklebacks] are a small and fascinating species,” Cunningham said. “They're armored, they have bony plates, they also have spines.”
Cunningham says that they usually find way more juvenile sockeye near the surface of the lake – up to 90%.
But in 2019, the weather was especially hot. Cunningham says the lake surface was almost seven degrees Fahrenheit hotter than normal. That year, the ratio flipped, and instead of mostly sockeye, they found 70% or more three-spined sticklebacks.
One possible explanation is that it was just too hot for the sockeye. Cunningham says that so far, Bristol Bay sockeye populations haven’t been hurt by rising temperatures.
“Warming over the past 10 years has actually been quite good in many ways,” Cunningham said. Less lake ice in the winter and warmer weather in the summer has led to more plankton, which means more food for sockeye.
In 2022, the inshore sockeye run was 79 million fish, an all-time record, according to the Alaska Department of Fish and Game.
But is is possible to have too much of a good thing. Cunningham says that the year 2019 might have been too hot for sockeye.
This year, Eberhardt is going to the research camp at Lake Iliamna. She’s hoping to do some experiments on sockeye and three-spined stickleback for her masters thesis.
One of the things they’ll be considering is whether three-spined sticklebacks, in specific conditions, could affect sockeye growth. One experiment would fill a pen in the lake with just sticklebacks, and then one with just sockeye, and then one with sockeye and sticklebacks. The fish will be able to eat their natural prey, and researchers will measure the growth of both species over the course of a few weeks.
One of the goals of Eberhardt’s research is to figure out if certain scenarios give either sockeye or sticklebacks a competitive advantage.
“It's a really big lake, so there is a chance that there's enough habitat and space for everybody to take advantage of these longer growing seasons without negatively impacting each other,” Eberhardt said. “That's kind of what we're hoping to tease out.”
Eberhardt’s research is funded by the Alaska Sea Grant and the Bristol Bay Regional Seafood Development Association, or BBRSDA. BBRSDA also helps fund the Bristol Bay Fisheries Report at KDLG.
Next year is Eberhardt’s final year at school. She says her research will hopefully be finalized sometime in 2026.
