The same skeleton as sharks
From the Acipenseridae family, sturgeon are characterised by a mainly cartilaginous skeleton, like sharks. They have rows of bony plates (scutes) instead of scales. Their ventral protractile mouth is preceded by 4 barbs which gives them a burrowing action. There are 24 varieties of sturgeons. They are all protected in annex II of the Washington Convention on International Trade in Endangered Species. They are threatened by bad water quality, late reproduction and the exploitation of their eggs: caviar.