Bristol Bay’s sockeye are returning by the millions to their natal streams. But not all salmon find their way back home — some find new areas to spawn.
Peter Westley is a Fisheries Professor at the University of Alaska Fairbanks. His research explores the act of salmon straying, and whether that’s a choice or a mistake.
“If a fish does stray, it tends to end up in a stream that's pretty close to its home stream, which sort of suggests that it's making the choice pretty close to home,” said Westley.
He says that while straying appears to mostly be an intentional decision, there are a lot of factors at play like age, habitat changes, and even peer pressure.
“The explanation for that is sort of rooted in collective behavior and sharing of information that it essentially takes,” he said. “If the group is bigger, it takes fewer individuals that are good at navigating and orienting to be able to lead the group home”
Westley says older fish tend to stray more.
“I'm only in my mid 40s, but my memory starts to slip a little bit,” Westley said. “So the idea is that, if you're older, you might just kind of start forgetting what home smells like.”
In addition to those memory lapses, a stream’s smell could change over the time a salmon is at sea. Some stream changes may even be significant enough that it’s no longer suitable habitat for spawning. In that case, Westley says fish will take their chances and head for new waters.
“These fish — they give their life for love,” said Westley, “so they’ve got one shot to reproduce. And so if they've got one chance, you might as well give it a go somewhere else”
Westley’s research focuses on a region that’s increasingly attracting stray salmon: the Arctic. He says the northward expansion of range has been observed in all five salmon species.
“Indigenous knowledge tells us that salmon have been around for a long time in the ocean and in the near-shore,” he said. “People have encountered them from time to time, but it does seem like it's starting to increase.”
He says a significant contributing factor to this expansion is warming water in the Arctic caused by climate change.
“They're sort of knocking on the door of the Arctic as it gets warmer and warmer and becomes more suitable to the full life stages of salmon,” Westley said.
According to NOAA, areas of the Arctic Ocean that are ice-free in August have warmed by 2.3 degrees Fahrenheit over the last four decades.
In the Arctic, Westley studies the range expansion of chum salmon. He says the chum that are moving into the region are coming from all over.
“About half of them come from Alaska populations, probably along the north slope in the western part of Alaska,” said Westley. “But the other half comes from the Asian side, so Korea and Russia—that's their ancestry. So we are having exchange between continents.”
But Westley says it’s not easy being a newcomer.
“Local fish have traits that make them well suited to those local sites, so they have essentially home field advantage,” he said. “So strays are coming into a sort of a foreign court and tend not to do as well.”
Despite the challenges of spawning in new territory, Westley says this is how every salmon population got its start, including Bristol Bay’s storied stocks.
“People should never forget that 10,000 years ago, Bristol Bay was covered in ice, and those great lakes were carved out by glaciers, and all of the salmon that now embody Bristol Bay, they were all not long ago in the grand scheme of things immigrants, they were they were coming from elsewhere,” Westley said. “So Bristol Bay was founded by strays.”
So far this season, over 40 million salmon have decided that Bristol Bay is still a good fit, and have returned to their home waters to spawn.
Get in touch with the author at jessie@kdlg.org
