The two organs that is responsible for ion exchange in bony fishes are gills and kidneys. They maintain the ion balance in the body of bony fishes.
The kidneys in the fishes are comparatively very small and they excrete a very small amount of urine to balance the ion in the body of the fishes.
The gills maintains the constant flow of water in the body of the fishes to compensate the ions in the body of the fishes in water, called as osmoregulation.
