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Glacier Salmon, Part 1

by Bill Hauser and Richard Nelson

This Fish Talk is somewhat different from most and I am fond of saying that I have been involved in the business of fish biology more than 50 years and I am still learning. Not long ago, I learned of “Salmon World” and more recently I encountered their website and this report by Richard Nelson. This is not new information but he has packaged and presented it quite nicely. (I have edited and deleted some sentences to reduce the length.) 

STRAYING SALMON

It was high summer in Glacier Bay National Park but I couldn’t see a trace of the ice that gave Glacier Bay its name. It was hard to imagine that just two centuries ago, Captain George Vancouver reported a solid wall of ice at the present mouth of the bay, with a vast glacier spreading away toward the north. Amazingly, thanks to the world’s fastest glacial retreat, this has now become a massive complex of open waterways more than 60 miles long.

I’d come here to meet Dr. Alexander “Sandy” Milner, a biologist from Birmingham University in England (formerly, from Anchorage). Each summer for 35 years Sandy has worked in Glacier Bay, where he studies the development of salmon runs in streams that emerge as the ice retreats.

Now we are beside one of those streams — Wolf Point Creek — with Sandy and two of his graduate students, Leoni and Jessica.

Let us consider the first thing everybody learns about salmon: They hatch from eggs in a river or stream, spend their adulthood at sea, and then flawlessly migrate back to spawn in the same stream where they were born.

Countless scientific studies prove salmon possess this amazing ability but research also shows a small percentage of salmon don’t come back home. Instead, they stray and end up spawning in streams another than their birthplace.

This fact is more than simply interesting…it’s also vital for understanding the history of salmon and their future in a changing world. Few people know this better than Sandy Milner. And as Sandy hustled to the spot where he had first begun studies in this stream more than three decades earlier. I imagined him working in this same place when he was a much younger man, and more importantly, when this was a much younger stream.

This day, everyone helped to set a couple dozen baited minnow traps in the stream, and then Sandy had a few moments to reflect. He explained that Wolf Point Creek is about 45 miles from the mouth of Glacier Bay, and sometime in the 1940s or '50s this very spot was still covered by an immense glacial face. But by 1977 — when Sandy’s research began — the rapidly shrinking ice had drawn back about a mile. At that time, the whole surrounding area — where the crushing ice once stood — was mostly bare ground except for small, scattered plants like fireweed. The creek itself was a torrent of murky 35 degree water. Today it’s far slower, shallower and clear, with summer water temperatures up to 62 degrees.

In fact, a bit later we all hiked to a deep pool farther upstream, cool enough for salmon yet warm enough for humans to take a dip. At the same time, I tried to envision the ice, several hundred feet thick, where we now had this idyllic swimming hole amid a green alder jungle, where thrushes and warblers chorus in the luxurious summer dawns.

The swim was a short break in a very long and concentrated workday. Back at their research site, Sandy and his crew emptied dozens of silvery “minnows” (i.e., salmon fry) into a tray of water laced with a mild anesthetic. Next they noted the species for every fish, recorded its length and weight, gently extracted its stomach contents into a vial for later analysis, then returned it to the stream unharmed. Months later in the lab, every tiny bit of food from thousands of trapped fish would be identified under a microscope to understand the diet for young pink, chum, and sockeye salmon, as well as Dolly Varden char that share the same waters. Modern biological research is remarkable for its focus on examining the meticulous details of living nature and converting these details into numbers for analysis, assuring strict objectivity and accurate conclusions. If this sometimes gets tedious, you wouldn’t know it by the animated energy of these scientists, who obviously loved their work and had completely saturated themselves with the wild beauty of Glacier Bay.

BIRTH OF A SALMON STREAM

In the late 1970s, still early in Sandy’s studies of Glacier Bay, another retreating glacier revealed the nub of a stream that became known as Stonefly Creek. Sandy Milner jumped on this rare chance to study a stream from the start of its existence, when it was totally devoid of life. Within ten years, Stonefly Creek had runs of pink salmon and Dolly Varden; and soon afterward there were also spawning coho and sockeye salmon. By 2001, up to 5,000 pink salmon were spawning in Stonefly Creek, and in Wolf Point Creek as many as 12,000 pink salmon had returned.

Genetic studies reveal each new stream is colonized by salmon from nearby waterways, so in the early years of Glacier Bay’s ice retreat strays came from outside the bay. In more recent times, streams like Stonefly and Wolf Point Creek are colonized by strays originating inside the bay. And as the ice continues to recede, these fish might themselves colonize new streams farther up the bay.

Life blossomed and diversified, so that by 2002 Stonefly Creek also had more than 80 species of freshwater invertebrates, mostly insect larvae and tiny shrimp-like creatures, which are essential food for young salmon. Analysis of the water chemistry also revealed salmon carcasses were helping to fertilize Stonefly Creek with nutrients brought in from the Pacific Ocean.

Sandy Milner’s research documents a process that’s been repeated countless times since Glacier Bay’s ice started retreating two centuries ago. In an astonishingly short time, rich communities of life have developed in these Glacier Bay streams, bringing brand new salmon runs to the Pacific Coast of North America.

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