THE EUROPEAN SEAS. 



207 



Most of the fishes which have been here enume- 

 rated, such as the Grey Mullets, the Gobies, the 

 Atherines, and flat-fishes, are well known to us as 

 being found elsewhere, in estuaries and brackish 

 waters ; but it is by the next series, or by the rela- 

 tive proportion of the cartilaginous fishes, that the 

 Black Sea and Sea of Azof are mainly characterized. 



Though the Sturgeon (Aciperser sturio) is taken in 

 all the Atlantic seas of Europe, yet it nowhere can 

 be said to be a common fish. It is only a rare visit- 

 ant to our coast, and the specimens taken are 

 always adults. It becomes somewhat more frequent 

 in the marine province to the north of ours, and 

 also in the Lusitanian and Western Mediterranean 

 region, but it is by no means frequent there. The 

 habits of the several species of this genus are not 

 the same. The common Sturgeon is the most 

 pelagic, or the greatest wanderer ; but, considering 

 the great distance at which they are taken up the 

 courses of the rivers which empty into the Elack 

 Sea and Caspian, that they spawn in these rivers, 

 and hibernate there, they would seem rather to be 

 river fishes which descend periodically to the sea 

 than sea fishes which ascend rivers. Though they 

 are captured more frequently in the larger Mediter- 

 ranean rivers than in Atlantic ones, yet even there 

 they only occur as single fish. 



As many as five species of Sturgeon have been 

 distinguished, and they all belong to that great 

 system of rivers which flow south and east into 



