What an interesting thread….particularly in that point about the 12 year period for Bream frame/skeleton growth and after that its basically fat/spawn/tissue that fluctuates. Makes sense..very interesting !
I think this is a key point and maybe one exception…I believe Carp can change frame/skeleton size many years after being at a stable weight if there is a significant change in their diet, for example a fish that may start to take more protein, a fish that starts to take Crayfish for example. I wonder if Chub could go the same way if there is a significant increase in a protein rich food source…the influx of Signal Crays for example…
Philip what I think is happening with carp is, because they are long lived 60+ years, they don't stop growing until they are about 40 years old.
However, they grow to the confines of the environment they in, and slow down the growth to a very slow pace.
Then they get an influx of food; crayfish get in, anglers start to pile in large quantities of bait, etc. I read the other day of one guy going through 625 kgs of boilies and 125 kgs of pellet in a season.
This influx of food lifts the constriction of their environment and they start to grow again in a spurt for some years.
This view is testable though scale readings and water temperatures, providing someone has kept them over a long period. Failing that, proxy records would have to be used. The best being ground temperatures for the area with a +/- 5 % variable.
Water warms up at about the same rate as the ground does. Less so on deep waters that stratify. But on waters that have a mean depth of less than 15 ft, it holds true. Rivers are different as they are subject to surface flow and the truism is more so btw.
I do know somebody who is doing some research into chub, water temperatures, spawning, etc but that's for him to report on, as it's his research.
By reading the scales from carp you could discern where the growth slowed down because of the environmental constrictions and the point where it started to spurt again. To avoid false readings you'd need to match it up with temperature records to make sure it wasn't down to natural conditions. A run of cold summers, which it's known the grow rate of any fish is slowed down. This is represented in the scale readings by the rings being closer together.
If the water/proxy records show it should have been good growing years and the rings show very slow growth for this time period. Then it would be safe to say that's when the fish reached the confines of their environment. If the growth rate then after showing the slow growth, then went back to wider spaced rings, some environmental factor(s) lifted the environmental constraints placed on the growth of the fish.
I wouldn't discount that it's possible with other fish, this could happen, but they may not live long enough for it to really show up as it would with carp.