One of our most prolific angling writers, John Bailey, has recently stated in Improve Your Coarse Fishing magazine that in his opinion two-tone fish are of uniform colour before capture and that the two-tone effect is caused by the stress of being caught. He says that this stress affects the heart’s capacity to pump blood effectively round the body and takes place especially when the fish is lifted from the water.
Theories in the past include the most popular one, that the fish was half buried in the bottom silt in a state of semi-hibernation through winter, the dark portion of the fish being the portion that was covered with silt.
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Yet another one was that two-tone fish were simply another variety of the species, ie, in some waters there are dark coloured fish and there are light coloured fish of the same species. Two-toners were just a mix of the two.
One thing that has always puzzled me is that the dividing line between the two colours is invariably a straight line and in the same position.
Right, let’s have a look at this latest theory from John Bailey.
He says the two-tone effect is caused by the stress of being caught and lifted from the water. So let’s mull over a few pertinent questions:
Why then, does it affect mainly carp and bream? (And char, but I’ll have to take his word for that). It does happen very occasionally with other species, but so rarely we have to ask the question, “Are those other species less prone to stress?”
Carp are a strong species and bream are quite fragile, yet it is these that are most prone to two-toning. Why?
I’ve caught literally hundreds of two-tone bream from a variety of waters. The waters where most of the two-tone fish were caught were those that came under least pressure. Shouldn’t it be the other way round if stress is the culprit?
I know a water where bream are caught practically every day and where I have never yet seen a two-tone fish. Are we to believe that these fish are a stronger breed, more resilient to stress?
I’ve caught, and seen caught, hundreds of carp, but I’ve seen less than a dozen true two-tone carp. Are we to believe that the great majority are not stressed by capture?
Why is it that only mature fish are prone to two-toning?
If the effect is particularly brought on by lifting the fish from the water why, on several occasions, when I’ve observed bream from the branches of a tree, in shallow water, on a clear, sunny day, have I seen two-tone fish swimming with the shoal? And note, this was in the old closed season, at least six months after any of those fish had been caught.
Why are the fish on fishmonger’s slabs not two-tone following being netted and left to die on the bottom of a trawler?
Why are those fish netted from aquariums and popped into plastic bags to carry home not two-tone?
Plenty of questions to ponder over there, and I must admit that I can’t provide any positive answers. Of all the theories I’ve heard my favourite has to be the parasite affecting the colour changing mechanism of the fish.
The stress theory, in my view, is the least likely answer.
Let’s debate it.
