Bony fishes and the marsh frog’s external structure

The skeleton of bony fishes is made of bone; the class has several orders. Sturgeon-like (bony-cartilaginous) fishes have an elongated body with 5 rows of bony plates, a mostly cartilage skeleton and a lifelong notochord. The Aral basin once had many ship sturgeons up to 2 m long, but today they are very rare; in the Amu Darya the rare false shovelnoses, listed in Uzbekistan’s Red Book, still survive. Salmon-like fishes (salmon, chum, pink salmon, trout) have an extra fin behind the dorsal fin; most go from sea to rivers to breed. Carp-like fishes are the commonest bony order: carp, barbel, roach; the grass carp and silver carp were acclimatised from the Far East. The lobe-finned coelacanth has a fin skeleton resembling land vertebrate limbs. Fish meat and roe are valued food, fish oil is a vitamin medicine, and waste yields fishmeal. Because many eggs and fry die in nature, fish are bred at special hatcheries and released into water bodies. Fishes are thought to have arisen from simple chordates like the lancelet. Rare species must be protected and fishing rules followed.