378 



BIOLOGY OF THE SEAS OF THE U.S.S.R. 



length of 12-5 cm, while the Caspian A. m. p. form reaches 14-0 cm. The 

 Black Sea pipefish {Syngnatus nigrolineatus) reaches 21-5 cm in length, and 

 the Caspian (S. n. caspius) — 23-0 cm. The fact that the Baltic herring, acclima- 

 tized in the Aral Sea, is much larger in size than that in the Baltic Sea (more 

 than 20 cm) is most interesting. According to some data, Nereis and some 



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10 

 WINTER 



TEMPERATURE 



Fig. 182. Two types offish migrations in the Mediterranean, Black and Azov Seas 



(Zenkevitch). 



prawns transplanted from the Sea of Azov into the Caspian are also larger 

 in size. 



It is very curious that a reverse relationship is apparent in the case of bull- 

 heads (Gobiidae) — the majority of them are much smaller in the Caspian Sea. 

 Thus, for example, in the Sea of Azov the largest size of Gobius melanostomus 

 is 23-5 cm, and in the Caspian Sea {affinis form) only 19-6 cm; Proterorhinus 

 marmoratus in the Sea of Azov and Pr. m. nasalis in the Caspian Sea are 

 respectively 11-5 and 7-0 cm in length, etc. Svetovidov explains this difference 



