Why are some fish reared in cages in the sea and some in tanks or ponds on land?
Mostly, fish that are raised in tanks or ponds on land are freshwater fish. Some, such as catfish, do well in still water and are farmed in ponds, while others, such as trout, require flowing water and are grown in tanks or raceways. Where freshwater is available, these are good methods of farming fish. However, freshwater is an increasingly scarce resource and it is difficult, now, to find areas where water is available that can be used for fish farming. There is much more salt water in the world. In fact, 97% of the earth’s water is in the oceans. Also, most of the fish we eat are saltwater fish. Because of this, much of the emphasis in the development of modern fish farming has focused on farming marine fish species in saltwater and this can be done in two ways. Either water can be pumped from the sea into ponds, tanks or raceways on land (‘pump ashore’ methods), or floating cages can be placed in the sea, where the natural forces of wind and tide provide the continuous flow of clea
