Canned salmon dating back to 1970s shows that marine mammals face increasing risks of intestinal parasitism

107th Annual Meeting: “A Change is Gonna Come”

August 3, 2022
For immediate release

Media contact: Heidi Swanson, (202) 833-8773 ext. 211, gro.asenull@idieh
Presenter contact: Natalie Mastick, moc.liamgnull@kcitsameilatan     

Over the past 40 years, whales and dolphins have become increasingly likely to consume prey containing parasitic worms that can cause acute gastritis in marine mammals, says new research from the University of Washington. The discovery comes from a unique source: cans of salmon processed between 1979 and 2019.

Salmon are intermediate hosts of parasitic intestinal nematodes known as anisakids, and marine mammals become the final hosts of these worms when they consume infected salmon.

An anisakid nematode, found in a can of salmon. Photo by Aspen Katla.

The three types of salmon that the researchers examined – pink, sockeye and chum – are all common prey of Alaskan marine mammals, including killer whales, beluga whales, northern fur seals, Steller sea lions and Pacific white-sided dolphins.

The study is the first to use cooked, canned fish to detect a trend in parasite burden over time.

Natalie Mastick, a Ph.D. candidate at the University of Washington, will present her findings at the Ecological Society of America’s 2022 Annual Meeting in Montreal, Quebec.

The idea for the project arose when a local seafood inspection company, the Seafood Products Association (SPA), contacted Mastick’s advisor, Chelsea Wood, about a collection of canned fish they had been storing in their basement since the 1970s. The SPA had stored the cans to determine how the product ages and how the cans hold up over time.

“The SPA had heard that Dr. Wood’s lab was working to uncover historical baselines of parasite infections in fish, and offered up their collection to us to determine if there’s been a change in parasite infections in the products,” said Mastick. “To our knowledge, no one had tried counting parasites in cooked, canned fish before, but I was eager to give it a try.”

The researchers dissected each salmon filet and quantified the number of worms per gram of salmon tissue.

Despite their presence in human food, the worms in canned salmon are cooked and present little risk to humans eating them.

“Even if someone ate a live parasite in a piece of raw salmon, humans are not the preferred host, so the parasite wouldn’t survive,” Mastick said. “The infected person would have food poisoning-like symptoms for a day or two, and then would be back to normal. There’s been some research on people developing sensitivities to the antigens in anisakids, even in cooked fish, but this seems to only be a problem if they eat a lot of the parasites.”

Steller sea lions are one of the final hosts of anisakids. Photo by U.S. Fish and Wildlife Service, CC BY 2.0.

The worms can, however, cause problems for marine mammals, particularly when a population is small and already under pressure from other stressors.

Mastick and her team found that marine mammals consuming chum and pink salmon have experienced an increasing risk of intestinal parasitism over the 40-year study period.

“Infectious diseases and parasite infections are more difficult to fight off when an immune system is already compromised by threats like bioaccumulation of pollutants,” said Mastick. “For example, the St. Lawrence Estuary beluga whale population is at 1% of historic population size, and faces a myriad of threats, including high levels of contaminants. Infectious diseases cause about a third of St. Lawrence Estuary beluga deaths, including anisakid infections.”

Mastick’s presentation, on Monday, August 15, at 4:15 PM EDT, is part of a session on Back and Forecasting in Ecology. This session includes additional talks on:

• Investigating changes over 120+ years in North-west Atlantic marine food webs using seabird feathers – Molly Morrissey, Memorial University of Newfoundland
• Fewer but higher quality pollinator visits determine plant invasion success in simulated plant-pollinator networks – Sabine Dritz, University of California, Davis
• Improving the predictability and interpretability of co-occurrence modelling through feature-based joint species distribution ensembles – Francisca Powell-Romero, The University of Queensland
• Multimodel community forecasts of vegetation phenology: Results from year 1 of the NEON Forecasting Challenge – Michael C. Dietze, Boston University
• A century of ecosystem change in the North Pacific Ocean: using isotopes to investigate the trophic dynamics of sockeye salmon – Celeste N. Kieran, Simon Fraser University

COS 22-4 – Opening a can of worms: Historical change in infectious disease risk for marine mammals revealed by archived canned salmon

• Monday, August 15, 4:15 PM EDT
• 513A, Palais des congrès de Montréal
• Natalie C. Mastick (University of Washington), Rachel L. Welicky (Neumann University), Aspen Katla (University of Washington), Bruce Odegaard (Seafood Products Association), Virginia Ng (Seafood Products Association), Chelsea L. Wood (University of Washington)
• Presentation abstract
• Contact: moc.liamgnull@kcitsameilatan

2022 Annual Meeting in Montreal, Quebec
August 14-19, 2022Ecologists from around the world will converge on Montreal, Quebec, this August for the 107^th Annual Meeting of the Ecological Society of America. Thousands of attendees are expected to gather for scientific presentations on breaking research and new ecological concepts at the Palais des congrès de Montréal on August 14^th through 19^th, 2022.

ESA invites press and institutional public information officers to attend for free. On-site press registrants will be able to attend all scientific sessions at the conference and will have access to a press room where they can enjoy refreshments, internet access, a printer and an interview area.

A virtual registration option is also available; virtual media resources will include an online newsroom with press releases and tip sheets of potentially newsworthy presentations, as well as complimentary access to the full program schedule and abstracts. Virtual content will be limited for this year’s meeting and will include recordings of plenary sessions, a selection of presentation slides and audio and a Q&A platform to allow for on-demand interaction with presenters. Presentation slides will be available starting after the corresponding in-person presentation is delivered.

To apply, please contact ESA Public Information Manager Heidi Swanson at gro.asenull@idieh.

• Annual Meeting website
• Media information
• Press registration
• Program

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The Ecological Society of America, founded in 1915, is the world’s largest community of professional ecologists and a trusted source of ecological knowledge, committed to advancing the understanding of life on Earth. The 9,000 member Society publishes five journals and a membership bulletin and broadly shares ecological information through policy, media outreach, and education initiatives. The Society’s Annual Meeting attracts 4,000 attendees and features the most recent advances in ecological science. Visit the ESA website at https://www.esa.org.

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