40-Year-Old Salmon Cans Reveal a Hidden Sign of Ocean Recovery
- Presence of anisakid worms in 40-year-old canned salmon indicates a healthy marine ecosystem.
The post 40-Year-Old Salmon Cans Reveal a Hidden Sign of Ocean Recovery appeared first on A-Z Animals .
Worms in your fish. The mere thought causes most people to shudder and just say no thanks. But what if their presence is actually a positive sign? According to a new study , the presence of worms in the fish isn’t something that should sound the alarm. To the contrary, it is a sign that the fish came from a healthy marine ecosystem.
While finding worms in fish is usually unwelcome, certain types can actually indicate a healthy environment. According to Chelsea Wood, a University of Washington associate professor of aquatic and fishery sciences, finding a specific kind of tiny parasitic worm – an anisakid – is an indicator that the waters where the fish lived are healthy and thriving.
Anisakids are small parasitic worms that live in the flesh of fish, including salmon.
©WH_Pics/Shutterstock.com
She said in a recent article discussing the study, “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.”
In the case of the fish examined in this study – salmon from the Gulf of Alaska and Bristol Bay – the presence of anisakids was a welcome find.
How and Why Was the Study Conducted?
The waters of the Gulf of Alaska and Bristol Bay are home to some of the world’s most important salmon fisheries. The health of the entire ecosystem is supported by complex marine food webs. As climate change intensifies, scientists are eager to understand how the changes are impacting salmon populations and health. While they could measure current changes by studying fish caught in recent years, they had no baseline to understand how healthy the ecosystem was decades ago.
Bristol Bay has one of the world’s biggest salmon populations.
©liveyourlife/Shutterstock.com
Natalie Mastick, currently a postdoctoral researcher at the Peabody Museum of Natural History at Yale University , came up with a novel approach while she was working on her doctorate at the University of Washington in Seattle. She turned to decades-old tins of canned salmon to get the data.
The canned salmon used in the study was supplied by the Seattle-based trade group Seafood Products Association. These cans had been preserved for quality control purposes but were no longer needed.
The tins contained fillets from four different salmon species collected over 42 years in the Gulf of Alaska and Bristol Bay. Mastick and her team opened and examined 178 cans, dissecting the preserved fish fillets and counting the anisakids embedded within them. The presence of anisakids is one indicator of the strength of the marine ecosystem.
What Did the Study Find?
Mastick and her team discovered that anisakid levels increased in chum and pink salmon caught and canned between 1979 and 2021. Coho and sockeye salmon, the two other species studied, showed parasite levels that remained steady.
Mastick, lead author of the study, said in the article about the study , “Anisakids have a complex life cycle that requires many types of hosts. 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.” The presence of enough hosts to allow the anisakids to thrive could be a sign of a stable ecosystem.
Pink salmon congregate in Alaska waters.
©Troutnut/Shutterstock.com
As to why two salmon species showed anisakid level increases while two remained unchanged, researchers couldn’t draw a definitive conclusion. Different anisakid species need their own combination of hosts to thrive. While the canning process kept the parasites’ outer structure intact, the internal features that scientists would normally use to differentiate the different anisakid species were destroyed.
Why Anisakids Are a Gauge of Marine Ecosystem Health
These tiny parasites start out as free-floating organisms in the ocean. When a tiny creature like krill eats them, the anisakids begin their long journey up the food chain. Krill infected with anisakids are eaten by larger predators, which in turn are eaten by even larger predators. This pattern continues until the anisakids eventually reach marine mammals. Once a marine mammal ingests the anisakid-infected fish, the parasites are finally able to reproduce. Their eggs are released back into the ocean, and the cycle starts over.
Seals are one marine mammal that anisakids rely on to reproduce.
©Nick Pecker/Shutterstock.com
As Mastick noted in the article, “Anisakids can only reproduce in the intestines of a marine mammal, so this could be a sign that, over our study period – from 1979 to 2021 – anisakid levels were rising because of more opportunities to reproduce.”
If the marine environment is compromised and a necessary host is not available, anisakids can’t complete their life cycles, and their numbers go down. That’s why finding anisakids in the canned salmon was a potential indicator that the marine environment over the decades studied was relatively healthy.
Why Are Anisakid Levels Rising?
Mastick believes there are several reasons that could be contributing to rising anisakid populations. One is the Marine Mammal Protection Act of 1972. It helped populations of many marine mammals, including seals and sea lions, recover after years of decline. Growing marine mammal populations give anisakids more opportunities to reproduce. The Clean Water Act, enacted in 1972, could also be a factor.
The post 40-Year-Old Salmon Cans Reveal a Hidden Sign of Ocean Recovery appeared first on A-Z Animals .
