You may want to think twice before you order your next sushi dinner. New research published in Global Change Biology has revealed that the a parasitic worm known as Anisakis is 283 times more likely to be in your fish than it was in the 1970’s.
Also known as whale worms, the parasite can cause vomiting and diarrhea in people who ingest them. The good news (and bad for those who prefer their fish fresh) is that freezing or cooking the worm filled fish will kill the worm. As well, the worm is large enough for chefs to visually see them to remove the worm while preparing the fish.
Researchers analyzed hundreds of global scientific studies published since 1967 to assess the number of works per individual fish. Overall, the data included more than 55,000 specimens and 215 fish species.
The first year for which the researchers had sufficient data was in 1978 where scientists reported finding less than one whale worm on average per 100 fish. By 2015, they were finding more than one Anisakis worm on average per individual fish. This number was found for almost all fish species studied across all geographic regions.
The increased number is very concerning for a wide range of species as the worm can be passed on from krill to squid to fish to whales and dolphins. Populations of all hosts could be at risk if the abundance of the worm in a given animal is too high.
Possible explanations for why the higher percent of worms are being found is that populations of the hosts are on the increase as well. For example, as whale population have increased due to more protections, the large marine mammals provide for the ability for the worm to increase in population too.
Another possible explanation for the parasites’ abundance is that the parasites’ life cycles might be speeding up as ocean waters warm due to climate change.
The team of researchers are now studying museum fish specimens that go further back in time to determine whether today’s worm populations are a sign of longer-term environmental decline, or rebound from human damage to the ocean and its inhabitants.
The team is also investigating what such a high parasite load might mean for those marine mammals, focusing on a struggling killer whales population off the U.S. West Coast.