A major change in the philosophy underlying the activities of biologists took place in the 19th Century. It became clear that there was more to Biology than merely describing the structure and relationships of animals and plants. These organisms should be manipulated to the benefit of Mankind by improved husbandry and especially by selective breeding. Fish were no exception and increasing interest in marine and freshwater hatcheries in the late 19 Century led to a requirement for controlling reproduction, the optimal use of broodstock and the rearing of young life history stages.