Mushy Kingfish

[PROS]

Over the last 5 years I was lucky enough to catch fair few kingfish in the bay in various sizes, (thanks to a great friend who taught me how to catch these aggressive breed)

Pretty much one in every 3 kingfish had a very mushy meat once cooked.
We always blamed the icing procedure even though fish is always iced straight away, however you can always make a colder slurry, gut and fill with ice inside, etc...

Yesterday, we managed to catch 3 kings.
More than enough ice in the icebox but no salt water slurry, fish was even bled and brain spiked immediately. No gutting.
Got home within 4 hours and gutted immediately all and in to the fridge.
Eating the first fish, same problem very mushy, inedible and very bad taste.
2nd fish tonight no problems.

Doing a bit of research in the net come with completely different answer below,

.... due to occasional infection of the fish with a parasite called Kudoa, probably Kudoa thyrsites, which infects the muscle tissue of the fish but is not apparent in the appearance of the fish. On death of the fish the parasite releases enzymes which change the flesh to mush.

The fish infected can be Kingfish, Tuna, Mahi Mahi, Tailor, and many others.

So do not think you have been careless with the fish by not getting enough ice on them, as it has nothing to do with that. It is a big problem in fish farms. Some research suggests about 1 in 10 kingfish are infected around Sydney, less further south and more further north.

To be sure the fish is not infected one way is to cook a small sample before freezing, as the infection is usually right through the flesh.

Due to my great friend leaving me hungry for the day, I consumed some sashimi from this infected fish in the boat.
I wonder the consequences....

Max

[PROS]

Sashimi kingfish was great actually even though it was a sick fish.
Looks like I will survive after all.....

Why are some fish ‘milky’ when cooked? The ‘milky’ problem sometimes observed in cooked Yellowtail Kingfish and other species is due to a microscopic parasite (from the class Myxosporea), which forms spores in the flesh of the fish while it is still alive. The parasite occurs in fish caught in warmer waters.

Symptoms aren’t evident until the fish is cooked – in its raw state it is perfectly fine to eat. Once cooked however, the flesh collapses into a mushy mass, which looks and tastes unappetizing – although it is not harmful in its raw or cooked state.

The collapse in the flesh is due to the action of an autolytic enzyme called protease. It becomes active at certain pH levels and certain temperatures, and then breaks down the protein and elastin in the flesh, causing it to ‘melt’ into a mushy mass. It is most active at low pH (around 3) and at cooking temperatures. Ironically the fish’s taste and texture is unaffected if eaten raw.

Similar microscopic spore-forming parasites are seen in other species of fish including Swordfish, Barracouta, Lemon Sole, Hake and Flounder. In raw Yabbies and Prawns the presence of this parasite is indicated by a white milky-coloured flesh instead of the usual translucent flesh; it is not evident in cooked crustaceans, as the flesh turns white anyway when cooked.

[bluefin59]

Fi have seen it a couple of times in kingies and we have caught heaps of them over the years but not very often usually get the mushy flesh thing with dollies that haven't made it too the ice quick enough ...Matt

[The Black Unicorn]

Have had it in the past too. All the fish that were caught one day had it. 3 or 4 from memory. All these fish were caught in summer in shallow water around the group. Water temp around 26 deg. I always thought it may have had something to do with the warm water. Have since caught some from deeper water with no issues.

[nathan dumschat]

That's Essay fix, I do not eat the rubbish we use them for red emperor bait, Nathan

[phantomphisher]

Quite unavoidable. They only start acting on the flesh once the fish dies, then it degrades in a matter of time (hence the decent sashimi). No amount of ice can save a fish from it. Should have no effect whatsoever on you though, eating the parasite isn't harmful to humans from everything that I've read.
Shame that it happened to you. It really does suck.

[GBC]

It only breaks down the proteins in the presence of heat - hence they fillet fine and freeze well. Only when you throw them on the bbq does it all go downhill. Totally unavoidable and undetectable (unless there is a kit like a cig kit?) and a good reason to plan to serve anything but dollies or kingys if you have the whole family coming for dinner and no backup plan - been there.

[PROS]

I see commercial opportunity to make a calamari/octopus tenderiser out of this parasite in low doses, instead of usual milk or kiwi fruit fix....

[deegee]

Have had it in the past too. All the fish that were caught one day had it. 3 or 4 from memory. All these fish were caught in summer in shallow water around the group. Water temp around 26 deg. I always thought it may have had something to do with the warm water. Have since caught some from deeper water with no issues.

I tend to agree with this theory, I have noticed that it is more likely to occur with fish caught in summer and much less likely with fish caught in winter.

I've also been told that it is seldom found in fish caught in the colder waters off Vic or SA even in summer.

[Aussie123]

Kudoa only affects the fish after it has been killed and the parasite releases an enzyme into the muscle tissue which causes the flesh to break down.
After about 2 hours you can begin see which fish have been infected by pressing down on the skin with your thumb or finger.
On a good fish the thumb mark will come back out but with an infected fish the thumb mark will stay depressed into the flesh.
When I fished commercially for Kings,it was probably only 1 out of several hundred fish that carried the parasite.
I could catch hundreds and not see it but occasionally a school of fish would turn up and it would be very prevalent.
Whilst unloading every Kingfish catch off the boat we would test every fish by pressing on it and discard any fish that were sus.
The longer the fish has been dead, the easier it is to see and any fish in the box for a full day or overnight will feel like they have flesh that has been pulverized with a base ball bat.

[Ben D]

In kings in Moreton Bay, its usually not Kudoa, but another myxosporean parasite Unicapsula seriolae, which is also related to cnidarians (jellyfish). The enzymes from Kudoa makes the flesh mushy once the fish dies and before it is cooked. Unicapsula only makes the flesh mushy once its cooked slowly. If you ice affected kings immediately and cook them quickly, like on a hot BBQ, there is a chance you can get away with it without it becoming a major issue. Unicapsula is very common in Moreton Bay kingfish, most of them have it, but only really heavily infected fish go mushy. How do I know ? I look at their flesh with a microscope and view the spores, so I know how many are in there, what type of spores they are (Kudoa have 4 polar capsules, Unicapsula only one), and once I know this I therefore know how best to cook them. See http://onlinelibrary.wiley.com/doi/1...340.x/abstract

[GBC]

Sent from my iPhone using Tapatalk

[Moonlighter]

Ben, thanks for that info. Great to have some scientific input here on occasions, between you and Daryl we have some great resources on this forum!

i gathered that these parasitic infestations are more prevalent in hotter water, and thus the Kings caught around Sydney in colder waters are less affected - is that right?

I also recall that some years ago there was a proposal from some mob to establish fish farms in Moreton Bay, with YTK's one of the planned species to be grown, until a number of factors including the likelihood of this parasite issue, put paid to that idea?

cheers

[NAGG]

never had any issues with mushy kingfish caught in waters south of South West Rocks (NSW) ..... nor in NZ - but have experienced it in Qld waters & have commonly heard of the problem in Qld .


without doubt the best eating qualities have always come from fish caught in cooler waters


Chris

[Ben D]

Ben, thanks for that info. Great to have some scientific input here on occasions, between you and Daryl we have some great resources on this forum!

i gathered that these parasitic infestations are more prevalent in hotter water, and thus the Kings caught around Sydney in colder waters are less affected - is that right?

I also recall that some years ago there was a proposal from some mob to establish fish farms in Moreton Bay, with YTK's one of the planned species to be grown, until a number of factors including the likelihood of this parasite issue, put paid to that idea?

cheers

No worries,

Most myxosporeans have an indirect lifecycle and in the case of Unicapsula, it is likely the intermediate host is a tropical species of some type of polychaete or oligochaete worm that does not occur further south. This would explain why the kingies down south don't appear to have the mushy flesh issue near as often (if at all, although I could imagine some northern kingfish travelling south during the summer months could cause trouble). The lifecycle of Unicapsula is not known, however, perhaps a good student project that one...

re: the Moreton Bay fish farms, it was more a political agreement I think at the start - if they had talked to someone who actually knew about aquaculture and the biology/diseases of the species they were talking about culturing, they would not have even considered the proposal, nor would they have wasted the money they did. Just ignorance really.