Researchers find parasite trends in decades-old canned salmon.
Researchers at the University of Washington have used 50-year-old canned salmon samples to identify long-term trends in parasite prevalence across North Pacific ecosystems.
The project began after the Association of Seafood Producers contacted ecologists Natalie Mastick and Chelsea Wood about disposing of aging quality-control stocks. Some of the cans, originating from Alaska processors, dated back to the late 1970s. The researchers examined 178 tins covering chum, coho, pink and sockeye salmon harvested between 1979 and 2021 in the Gulf of Alaska and Bristol Bay.
The samples contained anisakid marine worms, typically about one centimetre long and harmless to humans once cooked. Although often associated with product defects, anisakid presence is linked to ecosystem function because the parasites rely on a food-web sequence that includes krill, fish and marine mammals.
According to the study, published in Ecology and Evolution, worm counts increased over time in chum and pink salmon, while remaining broadly stable in coho and sockeye. The researchers suggest the rise indicates the parasite has continued access to required intermediate and final hosts, implying a stable or recovering ecosystem.
The team was not able to determine the precise anisakid species present in the samples, leaving open the possibility that some species are expanding while others are unchanged.
The study highlights the value of legacy food archives as sources of ecological data, enabling multi-decade assessments that would otherwise be unavailable.
