Is heat conducive to carp growth?

Many anglers are careful, that carp only grow to impressive sizes in warm climates. However, it turns out, that there are other factors as well.
Water reservoirs in southern Europe have warmer water all year round. For this reason too, carp have a much faster metabolism, they forage more often by eating more food, and thus reach impressive dimensions.
Does the above statement seem known from somewhere else?? Or maybe you think so too? if so, I will be happy to share with you my own theory on this topic and try to explain, why I believe, that the above view on the growth and reproduction rate of carp in natural water bodies, is the cause of so much misunderstanding.
I often get extremely fancy theories, for example, fish have recently grown to larger sizes due to the continual warming of our planet's climate. I personally doubt it very much. After all, fish reached record sizes many years ago, before discussions about the "greenhouse effect" even started. For example, if no one is puzzled by the fact, that in the North of Russia, Scandinavia or Alaska, pikes, perch, trout, salmon, sea ​​trout, zander and chub grow to such enormous sizes? “But they are coldwater fish – many of you will answer. Fish that feed mainly on the bottom, such as bream, catfish and carp, however, they grow to record sizes only in a very warm climate ". Are you sure?

Giant fish in the north

In some Danish and Swedish lakes, bream very often grow up to seven kilograms; even in northern Sweden it is possible to catch bream weighing 5 kg. „No, and sums – these fish definitely need to live in warm water, to reach large sizes?”
Also, this "theory" is not confirmed in reality. Totals weighing over 100 kg were also caught many times in Sweden.
“But the carp definitely need warm water. So far, very few large carp were caught in the north. This is the best proof, that these fish grow to the largest size only in warm climates ".
I also disagree with this statement, if only for this reason, that in Scandinavia and Alaska, carp weighing over 20 kg. It is true that summer in those latitudes is very hot, however, the winters are long and cold. However, carp do not mind and many of them grow up to the weight of over 25 kg.
Danish fisheries are covered with such a thick layer of ice from time to time in winter, that you can drive a car on it without the slightest fear. So please imagine, how cold the climate is there. Nevertheless, the carps living there are really big.

Frosty carps

The geographical location of the fishery and the prevailing climate there do not determine the growth of carp. In Hungary, for example, carp weighing more than 30 kg, although winter, with really cold days, lasts over a hundred days a year in Puszta.

So that the carp can grow to great sizes, and this applies to all reservoirs, four basic conditions must be met. Fish must have:
1. genetic predisposition;
2. unlimited amount of natural food;
3. stress-free life (none, they live in should not be caught by anglers or only to a minimum extent);
4. an unpolluted environment.

If these four points correspond to reality, carps grow to the largest size, Carps can adapt to almost any living conditions. The water temperature does not matter in the slightest. A good example of this are the alpine lakes in Austria and Switzerland. Some of them are home to giant carps, although in winter these reservoirs freeze for several months.

Carps weighing more than are certainly living in the lake near Bied in the Slovenian Alps 25 kg (one such fish broke literally a few centimeters in front of the landing net) and 50 kg totals.
If cold water were to inhibit growth, why the fish in the Twente canal in the Netherlands are getting bigger after each winter, even in fisheries far away from the hot water supply? Between the West Hengelo Bridge and the Deldon Bridge, fish weighing regularly are caught 15-20 kg (however, much less in much warmer water in Hengelo itself). Only two of the four factors I have mentioned work in this fishery (a large amount of food and the mat fishing pressure). The size of the carp likely depends on the conditions, in which the fish live for the first fifteen years. If four are met during this period, the aforementioned conditions, the fish is reaching record sizes, In the French Lac Cassien lake, many juvenile carp are growing at an impressive rate. Most of these fish, however, are restocked and lack the appropriate genetic makeup, characteristic of the giant carps that naturally occur in this lake.