Canned salmon is the unlikely heroes of the casual Nature Museum of Natural History, with decades of Alaska marine ecology, preserved in brine and tin.
Parasites can tell us a lot about the ecosystem because they are usually in the business of several types. But unless they cause any major problem for people, we have not historically paid much attention to them.
This is a problem for parasite environmentalists, such as Natalie Mastik and Chelsea Wood of the University of Washington, who were looking for a way to have the effects that parasites have on the Pacific northwestern marine mammals.
So when Wood receives a call from the Seattle Seafood Association in Seattle, asking if she would be interested in taking dusty salmon boxes – dating from the 70s of the last century – from their hands, her answer was, unequivocally, yes.
The cans have been set aside for decades as part of the process of controlling the quality of the association, but in the hands of environmentalists they have become an archive of well -preserved patterns; Not from salmon, but from worms.
While the idea of worms in your canned fish is a slightly rotating stomach, these approximately 0.4-inch (1-centimeter) marine parasites, Anisakidi, are harmless to humans when killed during the preservation process.
“Everyone accepts that the worms in your salmon are a sign that things have gone wrong,” Wood said when the study was published last year.
“But the life cycle of Anisakid integrates many components of the food network. I see their presence as a signal that the fish in your plate comes from a healthy ecosystem.”
Anisakid Worm (Circle in Red) in Canned Salmon. (Natalie Mastik/University of Washington)
Anisakids enter the food net when eaten by Krill, which in turn are eaten by larger species.
This is how the Anisakids find themselves in salmon and eventually the gut of marine mammals, where worms complete their life cycle by reproducing. Their eggs are separated into the ocean from the mammal and the cycle begins again.
“If the host is not present – marine mammals, for example, Anisakids cannot complete their life cycle and their number will fall,” says Wood, a senior newspaper author.
178 TIN CANS in the Archive contained four different types of salmon caught in Alaska and Bristol Bay during a 42-year period (1979-2021), including 42 CHUM boxes (Oncorhynchus Keta), 22 Coho (Oncorhynchus Kisutch), 62 pink (Oncorhynchus Top), and 52 SOCKEYE (Oncorhynchus Neka).
Although the techniques used to preserve salmon do not support the worms in a virgin state, the researchers have been able to dispel the fillet and calculate the number of worms per gram salmon.
They found the worms increased over time in Chum and Pink Salmon, but not in Sockeye or Coho.
“Seeing that their numbers increase over time, as we did with pink and pine salmon, shows that these parasites have been able to find all the right hosts and reproduce,” says Mastik, a leading author of the newspaper.
“This may indicate a stable or restoration of the ecosystem, with enough hosts for Anisakidi.”
The spread of canned salmon samples available for any type of salmon over every decade. (Mastick et al.. Ecology and evolution2024)
But it is more difficult to explain the stable levels of worms in Coho and Sockeye, especially since the preservation process makes it difficult to identify the specific types of Anisakid.
“Although we are confident in our family level identification, we could not identify [anisakids] We found the species at the level, “the authors write.
“So it is possible that parasites of an increasingly greater look may infect pink and salmon, while the parasites of a stable appearance tend to infect Coho and Sockeye.”
Mastik and his colleagues believe that this new approach – Dusty Old Cans has become an environmental archive – can nourish many more scientific discoveries. They seem to have opened a lot of worms.
This study has been published in Ecology and evolution.
A larger version of this article was published in April 2024.S