388 THE FRESH-WATER KISIIKS oF Kl'Kol'K. 



Acipenser ruthenus (LiN.). The Sterlet. 



The Sterlet is found in the Black Sea, the Sea of Azov, and Caspian, and 

 all the rivers which flow into them, though it is absent from the south of the 

 Caspian, and only stray specimens are occasionally taken in the River Kur. 

 It is also abundant in the rivers of Siberia, which fall into the Arctic Ocean, 

 and especially affects the Irtish. According- to Dr. Grimm, the Sterlet made 

 its way about forty years ago through canals into the Northern Dwina, which 

 flows into the White Sea by Archangel, and here, under the cold conditions 

 which are so necessary for it, it has not only settled down and become abundant, 

 1 ut acquired a short blunt snout and an arched back, and has developed a 

 flavour which makes it more prized in St. Petersburg than the Sterlet from the 



Fig. 177. ACIPEXSElt RVTHENUS 



Volga. Indeed, in that river it deteriorates in flavour the farther south it is 

 taken. It ascends the Danube regularly as far as Vienna, is not rare at Linz, 

 and is often got at Passau and in Bavarian waters. It rarely reaches a length 

 of three feet, and in the Danube is seldom over two feet. Fishes weighing 

 over seven pounds are scarce, and the demand has been so great that in the 

 Volga and Dnieper, Sterlet only four or five inches long are now captured. 

 The flesh and roe of this species are more esteemed than those of the larger 

 Sturgeons (Fig. 177). 



The fish is four-and-a-half times as long as its head, and there is very 

 little difference between the width of the back of the head and the fore part 

 of the body. The body is highest directly under the third dorsal shield, and 

 this measurement is half as long as the head. The small snout is rather flatly 

 compressed, and three times as long as the mouth aperture is wide. The 

 upper part of the head is covered with irregular radiated shields, which have 

 raised central points and correspond in position and relation to each other with 

 the bones which in most vertebrates roof-in the head. 



The forms of the shield are altogether characteristic, and the strongly ele- 

 vated central point gives the head a curious tuberculated appearance. The 



