Each year, a small team of biologists make the drive up to Salmon Lake near Nome to pour giant tubs of chemicals in the water. It’s part of a decades-long project that seeks to protect salmon populations in the region.
The effort is led by Norton Sound Economic Development Corporation, the organization in charge of the region’s Community Development Quota.
Each year since 2007, NSEDC has dumped an "Alaska Mix" of nitrogen and phosphorus in the lake – two ingredients microscopic phytoplankton need to grow. More phytoplankton typically leads to more zooplankton, which salmon feed on.
NSEDC Fisheries Biologist, John Wade, said the fertilizer helps build a salmon’s diet from the bottom up.
“If there's more nutrients in the lake, more plankton, they're able to feed off of it more and just have a better chance of actually going out to the ocean and not getting eaten right away, or they have a better chance of competing in the wild,” Wade explained.
Both chemicals, nitrogen and phosphorous, already occur naturally in the lake. Wade said a common source are the salmon themselves, which seasonally return to the lake, spawn, die and decay in the water. But when there are weak salmon returns, the amount of nutrients in the water declines too.
"In those years where we didn't have as much fish, it was more important that we got more fertilizer out," Wade said.
To get the fertilizer in the water, NSEDC deploys an aluminum-hulled Lund boat fitted with a 110 gallon tank. Specially designed pipes suck in water as the boat glides across the lake, mixes it with the chemicals, and spits it out the back.
Crew Leader, Donald Smith, takes turns piloting the boat with his sister and fellow Crew Leader, Katie Smith. Depending on the day, he deploys a few different methods to get the fertilizer evenly distributed.
“You do like a toilet flush kind of dealio, where you just get smaller and smaller circles as you're going around,” Smith said. “Or you can do the zig-zag, you just go up and down hot dog style or hamburger style.”
What does the science say?
Fish fertilization in Alaska goes back to at least the 1970’s, when the Alaska Department of Fish & Game operated the Division of Fisheries Rehabilitation, Enhancement and Development (FRED).
“They did a lot of enhancement and rehabilitation projects and that petered out in the late 70s, early 80s, as funding dried up,” ADF&G Research Biologist, Heather Finkle, said.
Finkle is in charge of ADF&G’s Kodiak Island Limnology Laboratory, which tests samples from lakes and streams across the state. She said FRED ramped up its fertilization efforts in the 80’s, long before it came to Salmon Lake.
“They came up with you have to go and collect a baseline of limnological data first, and then you can go from there, as far as how to build recommendations,” Finkle said. “They came up with an amount to fertilize based on all that data.”
FRED was effectively dissolved in 1993, but the practice of fertilizing lakes carried on. NSEDC data suggests Salmon Lake has been fertilized since at least 1997. Since FRED's dissolution, the practice has become a bit of a wild-west, with no direct oversight from ADF&G.
“Ironically, there's really not any permitting that I know of. It doesn't seem like it's really heavily monitored as far as, ‘how much fertilizer are you putting in this year?’ It's pretty much at the whim of whoever's fertilizing,” she said.
Finkle said Salmon Lake has seen several boom and bust cycles over the years, making it hard to know if the fertilization is working.
“In some sense, maybe it did work, and maybe the conditions were just right,” Finkle said. “But that's the thing with fertilization, in having looked at their data, there's no direct correlation between, or relationship between what you fertilize and the number of adults that return. That's the hard part.”
Since NSEDC took over the fertilization efforts in 2007, it has dumped just over 350 tons of fertilizer in the lake. Wade believes the program is now entering a “sweet spot”.
“Where we're not doing too much and but we're also not doing nothing as well,” Wade said. “I think if we would ever want to stop fertilizing this lake, we'd have to wean it off for a couple years, slowly, slowly, slowly, just to not stop all the way and salmon could crash.”
While the jury might still be out on if the fertilization is boosting salmon populations, Wade and Finkle agree its not causing any harm to fish populations. Wade said the team at NSEDC will monitor the limnology results, and like previous years make adjustments as needed.
