A yellowtail kingfish may seem completely ordinary on the cutting board yet still turn mushy by the time it’s served.
New Australian research suggests the parasite linked to the species’ notorious texture problem may be more common than expected — often staying hidden until cooking begins, an article from The Conversation shared on Phys.org reported.
Here’s what to know
By testing yellowtail kingfish caught in New South Wales, scientists found the myxosporean parasite Unicapsula seriolae in many of them, putting long-standing angler reports on a scientific footing.
According to The Conversation, the team found the parasite in 38.9% of fish sampled in 2024 and 2025.
It was the first scientific confirmation of the parasite in kingfish from NSW.
Most infected fish did not show the expected texture problem.
In 71.4% of positive samples, the flesh did not turn mushy after cooking, meaning most infected kingfish were asymptomatic.
Raw appearance is not a reliable clue, the researchers warned.
An infected fish can still look, smell, and taste normal — even when eaten as sashimi — with the texture problem showing up only after cooking or exposure to acid, such as in ceviche.
More background
Reports of kingfish going soft after cooking have circulated among NSW fishers since the 1990s, but they remained anecdotal for decades.
This study changed that by testing wild-caught fish from the state and directly confirming the parasite’s presence.
Detections of Unicapsula seriolae were limited to kingfish from Queensland and Western Australia, as well as aquaculture operations in Western Australia. The NSW results suggested that the parasite may be distributed more widely than many assumed.
Since the defect might not become obvious until a meal is already being prepared, anglers and consumers can end up wasting other food along with the fish itself.
If hidden infections are common, anglers, charter operators, and commercial sellers could all face growing pressure to better understand when and where mushy-fleshed kingfish are showing up.
What can be done?
Researchers worked with NSW anglers, spearfishers, and charter operators to collect kingfish tissue for sampling.
Thankfully, the issue was about quality and waste rather than a contamination scare.
Scientists have not yet shown that Unicapsula seriolae is definitively causing the mushy-flesh problem in every case. They also found that relying only on whether a fish turns mushy after cooking to identify the parasite’s presence would miss many infections.
While blind spots remain, progress is being made toward resolving this frustrating issue.
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Dining and Cooking