E. LÖNNBERG, THE ICHTHYOLOGY OF THE CASPIAN SE A. 



Perca fluviatilis Lin. 



The ■^>okun» is common in the Volga delta altiiough it 

 does not belong to the most important foodfishes of this re- 

 gion. It is caiight in seines together with other fishes 

 in the spring, but the greatest quantities are caught in 

 the autumn, when the fishes congregate for the purpose of 

 hibernating. It attains, now and then, a maximum weight 

 of 5 Russiau funt (a little more than 2 kilo). The first days 

 of May I found male specimens with flowing milk. The water 

 had then a temperature of +11° C. 



The perch of Volga seems never to exteud its wanderings 

 to the Caspian Sea. This is a remarkable difference in habits 

 compared with the Scandinavian perch whieh feels quite at 

 home in the Baltic. 



The three species of pikeperch which inhabit this region, 

 Stizostedium lucioperca (Lix.), Stizostedium volgense (Pallas) 

 and Stizostedium marinum (Kessler) are in the following 

 treated of together for the purpose of better allowing a com- 

 parison. Their relative measurements may be seen from the 

 following table: 



Total length 



% of total length: 



Length of head 



Greatest height of body . . . 

 Least » i> » . . . 



Prseorbital length 



Postorbital » 



Distance from snout to dorsal fin 



» Si» anal > 



> 5 » j ventral > 



Postabdominal length 



Base of I dorsal fin . 



» > II ; » . 



» '- anal » 



Length of pectoral fin 



> ■' ventral > 



Horizontal diameter of eye in % 



of the length of head . . . . 



