40-Year-Old Salmon Cans Unsealed: The Shocking Discovery Inside

Old cans of salmon, some dating back to the 1970s, are surprising tools for studying changes in marine ecosystems. These cans were originally kept for quality control by Seattle’s Seafood Products Association and recently handed over to researchers at the University of Washington. Their findings were published in Ecology and Evolution in April 2024.

When parasite ecologist Chelsea Wood received boxes of dusty, old canned salmon, she recognized a unique opportunity for research. Along with her colleague Natalie Mastick, they examined the contents of these rusted cans. Inside, they found anisakid worms—about one centimeter long—embedded in the fish section. While these worms might gross some people out, they’re harmless to humans post-canning.

Moreover, these worms serve as valuable indicators of ocean health. Wood explains, “People often think worms mean something’s wrong. But their presence indicates a healthy ecosystem capable of supporting diverse marine life.”

Understanding the lifecycle of anisakid worms sheds light on marine ecosystems. They start as eggs in the ocean, consumed by krill and then by fish like salmon. When marine mammals eat these fish, the cycle continues. If any part of this chain—like a decline in marine mammal populations—is disturbed, it can affect worm populations. This makes worm prevalence a good indicator of ecosystem stability.

By analyzing samples from 178 cans collected from the Gulf of Alaska and Bristol Bay from 1979 to 2021, the team tracked changes in worm populations over 42 years.

The study included four salmon species: pink, chum, coho, and sockeye. Researchers noticed that chum and pink salmon had increased worm loads over time, while coho and sockeye numbers remained stable. This suggests that pink and chum salmon populations were stable enough to support more parasites, indicating a recovering ecosystem. Mastick noted, “The rise in pink and chum shows these parasites found ample hosts, hinting at a stable ecosystem.”

In contrast, the stagnant numbers in coho and sockeye salmon pose questions. The canning process destroyed many worms, making it hard to identify species. The researchers could only make assumptions about different host preferences among the anisakid worms.

Despite the challenges, using expired canned fish as a biological archive is innovative. These forgotten tins allow researchers to study historic parasite trends without the cost and time associated with traditional fieldwork. This new approach could be crucial for understanding the health of our oceans, especially as ecological changes become increasingly urgent. These cans—once overlooked—now serve as remarkable time capsules of our marine history.

As we reflect on this research, it’s clear that even the most unexpected sources can provide significant insights into our environment. A recent survey from the National Oceanic and Atmospheric Administration (NOAA) reported that over 80% of marine species are still unexplored, pointing to the importance of ongoing research in this area.

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