That’s a problem for parasite ecologists, like Natalie Mastick and Chelsea Wood from the University of Washington, who had been searching for a way to retroactively track the effects of parasites on Pacific Northwestern marine mammals.<\/p>\n
Related: ‘Zombie Worms’ Have Mysteriously Vanished, Troubling Scientists<\/a><\/strong><\/p>\n So when Wood got a call from Seattle’s Seafood Products Association, asking if she’d take boxes of dusty old expired cans of salmon \u2013 some dating back to the 1970s \u2013 off their hands, her answer was, unequivocally, yes.<\/p>\n The cans had been set aside for decades as part of the association’s quality control process, but in the hands of the ecologists<\/a>, they became an archive of excellently preserved specimens, not of salmon, but of worms.<\/p>\n Watch the video below for a summary of the research:<\/p>\n While the idea of worms in your canned fish is a bit stomach-turning, these roughly 0.4-inch (1-centimeter) long marine parasites, anisakids<\/a>, are harmless to humans when killed during the canning process.<\/p>\n “Everyone assumes that worms in your salmon is a sign that things have gone awry,” said<\/a> Wood when the research was published in 2024.<\/p>\n “But the anisakid life cycle integrates many components of the food web. I see their presence as a signal that the fish on your plate came from a healthy ecosystem.”<\/p>\n Anisakids enter the food web when they are eaten by krill<\/a>, which in turn are eaten by larger species.<\/p>\n This is how anisakids end up in the salmon, and eventually, the intestines of marine mammals, where the worms complete their life cycle by reproducing. Their eggs are excreted into the ocean by the mammal, and the cycle begins again.<\/p>\n “If a host is not present \u2013 marine mammals, for example \u2013 anisakids can’t complete their life cycle and their numbers will drop,” said<\/a> Wood, the paper’s senior author.<\/p>\n Related: Microbes in Fukushima Found Surprisingly Unscathed by Radiation<\/a><\/strong><\/p>\n The 178 tin cans in the ‘archive’ contained four different salmon species caught in the Gulf of Alaska and Bristol Bay across a 42-year period (1979\u20132021), including 42 cans of chum (Oncorhynchus keta<\/a>), 22 coho (Oncorhynchus kisutch<\/a>), 62 pink (Oncorhynchus gorbuscha<\/a>), and 52 sockeye (Oncorhynchus nerka<\/a>).<\/p>\n Although the techniques used to preserve the salmon do not, thankfully, keep the worms in pristine condition, the researchers were able to dissect the filets and calculate the number of worms per gram of salmon.<\/p>\n They found worms had increased over time in chum and pink salmon, but not in sockeye or coho.<\/p>\n “Seeing their numbers rise over time, as we did with pink and chum salmon, indicates that these parasites were able to find all the right hosts and reproduce,” said<\/a> Mastick, the paper’s lead author.<\/p>\n “That could indicate a stable or recovering ecosystem, with enough of the right hosts for anisakids.”<\/p>\n But it’s harder to explain the stable levels of worms in coho and sockeye, especially since the canning process made it difficult to identify the specific species of anisakid.<\/p>\n “Though we are confident in our identification to the family level, we could not identify the [anisakids] we detected at the species level,” the authors write<\/a>.<\/p>\n “So it is possible that parasites of an increasing species tend to infect pink and chum salmon, while parasites of a stable species tend to infect coho and sockeye.”<\/p>\n![\"YouTube](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/02\/0.jpg\")
frameborder=”0\u2033 allow=”accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share” referrerpolicy=”strict-origin-when-cross-origin” allowfullscreen><\/p>\n![\"A](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/02\/NematodeInSalmon_Body.jpg\")
An anisakid worm (circled in red) in a canned salmon fillet. (Natalie Mastick\/University of Washington)<\/p>\n![\"A](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/02\/DegradedNematodeInSalmon_Body.jpg\")
A highly degraded anisakid found in canned salmon. (Natalie Mastick\/University of Washington<\/a>)<\/p>\n![\"Graph](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/02\/ece311043-fig-0001-m-642x352.jpg\")
The distribution of canned salmon samples available for each salmon species in each decade. (Mastick et al., Ecology and Evolution, 2024)<\/p>\n![\"Audition](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/01\/Mid-Article-Promos-Casting-Call-1-642x272.jpg\")
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