Analysis Shows Pink Salmon’s ‘Incredible’ Sense of Direction

Pink salmon. Photo: NOAA Fisheries.

Results of University of Alaska Fairbanks’ DNA analysis of a massive database on pink salmon shows a remarkable ability of the fish to spawn at nearly the same spot within streams that their parents did.

The project, which reviewed genetic data from over 30,000 pink salmon, taps into an ongoing study in Alaska’s Prince William Sound that has collected DNA samples from pink salmon carcasses since 2011. The Alaska Hatchery Research Program (AHRP) samples pink salmon in 30 streams, including five where researchers try to get samples from every salmon returning to spawn.

The AHRP is a collaboration of the Alaska Department of Fish and Game (ADF&G), nonprofit hatcheries, the fishing industry and academia, largely focused on the impact of hatchery fish on wild salmon populations. The database additionally provides much information for researchers looking at other issues.

“We can connect the parents and offspring from multiple populations, along with body size, when they were sampled and where they were sampled,” said Samuel May, the postdoctoral fellow at the University of Alaska Fairbanks College of Fisheries and Ocean Sciences (UAF CFOS) who led the study. “There’s all this fine-scale diversity that we didn’t really appreciate before.”

The study found that once the salmon return to a home stream or tideland after a journey of traveling thousands of kilometers, they generally spawn within 100 meters of the spot where their parents spawned.

Genetic analysis also highlighted distinctions between areas within the streams where pinks spawn. About 75% of the salmon spawn in intertidal areas, a zone affected by regular saltwater intrusion and apparently preferred by wild pinks. Hatchery-origin pink salmon tend to travel into freshwater areas of those streams to reproduce. There they may be more likely to mate with other fish that also were stocked by hatcheries in those locations. Their origins are also associated with a variety of biological differences, including body size and reproductive success.

May noted that pink salmon haven’t received the same attention from researchers as other salmon species because they’re often viewed as homogenous — spawning pinks are all two years old and roughly the same size. Through DNA analysis, researchers are revealing a more diverse species, which should help its ability to adapt as the climate changes, he said. “All this variation impacts the ability of this species to persist in the face of change.”

Peter Westley, an associate professor at the College of Fisheries and Ocean Sciences, who contributed to the study, and is a member of the AHRP’s Science Panel, said these findings are just the beginning and that within a few years, there will be over 200,000 pinks in their genetic database.

“We’re leaning on a dataset that’s had a ton of work put into it,” he said. “This is just the tip of the iceberg.”