Another very significant genetic impact is with temperature. In cold-blooded animals, the chemical reactions are controlled by temperature and are inherited. As an example, in some fish (char) the muscles work just fine at low temps while in bass they don't. Incubating and rearing salmonids in warmer water selects for the chemicals that work in warm water. They just don't work in cold. That is likely one of the main reasons why Chambers Creek Winters performed so poorly as wild spawners. They had been, for decades, spawned, incubated, and reared in warm water. In the wild, the water was 15-20 degrees colder; they died.