A decrease in salmon size could pose a threat to businesses and the Alaskan ecosystem
A new study in Nature Communications finds that the size of salmon returning to Alaskan rivers from the ocean has declined dramatically over the past 60 years.
Researchers from the University of California, Santa Cruz, and the University of Alaska at Fairbanks analyzed over six decades of data — from 1957 to 2018 — on over 12.5 million fish. The data looked at four different species of salmon: chinook, chum, coho, and sockeye.
Salmon are a critical part of both the economy and ecosystems in Alaska, and a decrease in size of the fish could severely impact both. Salmon transport nutrients for animals such as bears and insects from the oceans to small water bodies, and many fishermen depend on the fish for their livelihood.
“There are two ways they could be getting smaller — they could be growing less and be the same age but smaller, or they could be younger — and we saw a strong and consistent pattern that the salmon are returning to the rivers younger than they did historically,” corresponding author Eric Palkovacs, professor at UC Santa Cruz said in a press release.
So where does climate change come in? According to researchers, salmon are returning to freshwater streams at younger ages. “We know that climate drives changes in ocean productivity, and we see a consistent signal of climate factors associated with decreasing salmon size,” Palkovacs said.
Yet what, exactly, is happening in the ocean to drive this shift is still unknown. The researchers say uncovering those details will be their next step.