Two-Tone Fish

[GrahamM]

That was a really interesting theory Phil and I take it on board with all the other theories (except the stress one, which is ridiculous).

I think the exact truth - and again we can only speculate until someone does a thorough scientific study - is that two-toning can be caused by more than one factor, brain damage, damage to the colour changing mechanism, and old age probably being the most likely.

 

[BUDGIE BURGESS]

Quote "two-toning can be caused by more than one factor,brain damage,damage to the colour changing mechanism,and old age probably being the most likely"

If this is correct then why is John Bailey himself not two-tone?

 

[william kirkwood]

you have to turn"em over in frying pan
to brown "em both sides.
This stops the two-tone effect!

 

[Scott Thomson]

The only experience i have of this is in tropical fish (discus) a faulty filter caused the PH of my water to drop to about 4.3 the result of this was that my 5 discus turned black over the next few weeks the colour returned except that they were now showing a two-tone effect similar to the bream mentioned. As Discus normaly turn a darker shade when stressed i found on occasions that the front half would turn dark and the original colour would return at the rear. these fish bred on many occasions and never once were the fry ever two-tone, so perhaps its a combination of stress and water quality that effects them and bream seem to suffer more than most.

 

[Tony Miles]

Interesting thread, this. I am firmly of the opinion that the phenomenon is centred around melanin, the black/dark brown pigment present in all living creatures. Varying amounts of the pigment account for the varying body tones of humans, from pure white to jet black, and all graduations in between. Melanin is an important agent in protecting against the effects of ultra violet radiation from the sun. That is why albino humans (showing severe melanin deficiency) are so prone to sunburn.
Studies have shown in humans that there are specific melanin sensitive reagents in cell walls from brain tissue, and that such cells melanise during infection, particularly fungal infections. At the most severe, this can lead to non malignant skin cancers, with characteristic skin darkening effects, right up to malignant melanoma, where large areas of skin can be almost black.
Localised or irregular skin darkening can also be a symtom of progressive pigmentation imbalance as a result of ageing. Even in healthy humans, it is very common for us to develop brown or black spots or patches as we get older.
I am not saying that our two tone bream have skin cancers, but I can accept a strong possibility that, as the fish grow, the odd individual will develop pigmentation imbalance as a result of a fungal infection. And why should not the odd specimen develop a malignant skin tumour. All other living creatures do.

 

[Mike Fidler]

Genetic irregularity. Occurs in all creatures, birth marks and what we used to call port wine stains on humans, caused as Tony says above by melanin imbalance. Does it happen in bream as well? It's got my vote at least.

 

[Phil Hackett]

Some more thoughts on two-toning brought on by Tony’s comments. Fish do not contain calcium in the skeleton structure it is stored in the scales only. Therefore as the fish gets older like humans it starts to deplete and the body can not metabolise new inputs as efficiently as it did in the early to middle age. This may possible account for the darkening of the scale. I should point out that the flesh under the scales in my experience shows no signs of darkening.

 

[john conway]

Sorry to drag up an old topic up once again, but I've just read the bream section of Graham's book “Advanced Coarse Fishing” on page 74 he states "A few hours after death a two tone bream reverts back to one colour, the lighter shade". In these circumstance I'm of the opinion that two toning may be as previously suggested, a genetic defect affecting the central nervous system. Other reasons for colour changes I do not think would result in the abrupt geometrical changes in the colour pattern we associate with two toning.
By the way Graham, excellent book, when are you going to release an updated version?

 

[Steve Muir]

Phil
Could it be damage or disease to the cells in the dermis?
As the colours seen in fish are produced by cells in the dermis
(Melanophores,Erythrophores,Xanthophores,Iridophores)
i would think fish can change colour from one moment to the next by movement of melanin
grains within each cell.

Any thoughts on Chromatophores or Guanin

Regards Steve