This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: If you're a keen angler and regularly catch yellowtail kingfish (Seriola lalandi), you may have encountered instances of the fish's flesh turning mushy and unpalatable once cooked. Some have said it's a bit like trying to eat wet newspaper.
This can be disappointing for the angler and the hungry guests you've invited to dinner. It is also a waste of food—and of the fish's life. It's often hard to pinpoint which fish will turn mushy when cooked, as they can look, smell and taste the same when raw, such as when served as sashimi.
The issue only appears once the fish is cooked or prepared as ceviche. In other words, you need heat or a pH change for the problem to reveal itself. The mushy flesh problem is associated with the parasite Unicapsula seriolae, but it's too soon to say it's definitely the cause—that research hasn't been done yet.
What we do know is that this parasite shows up in many kingfish that turn mushy when cooked. Now, our research suggests infection with Unicapsula seriolae may be more widespread than first thought. In fact, we found even flesh that doesn't go mushy after cooking can still be infected.
I've been fascinated by the mushy kingfish problem for more than 15 years, following my own encounters in the waters off Sydney, the mid north coast of New South Wales and at the dinner table. There are reports dating back to the 1990s of people in NSW catching kingfish that later turn mushy when cooked. But our research aimed to go beyond anecdotal evidence, so we scientifically tested for and detected this parasite in kingfish caught in NSW.
For the first time, we showed it is present in kingfish from NSW. Scientists had previously only tested for and detected this parasite in kingfish caught in Queensland and Western Australia, and in aquaculture settings in Western Australia. Our recent research involved working closely with NSW-based anglers, spearfishers and charter operators to obtain donations of kingfish tissue in 2024 and 2025.
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