i6o BRITISH FISHERIES 



there is the well-known habit of the salmon, 

 which ascends rivers to deposit its spawn in the 

 upper reaches. The spawning migration of the 

 eels is a very extraordinary one, and, in spite of 

 much laborious research, this is very imperfectly 

 understood. Fresh-water eels with ripe repro- 

 ductive organs are never found in the rivers. 

 When the breeding season approaches, a change 

 in the appearance of the fish — the assumption of 

 a " bridal-dress " — ^has been observed, and then a 

 migration into the sea takes place. There is little 

 doubt now that, having once spawned, the fish 

 does not return into the river, but dies soon after 

 the eggs have been deposited. This is also the 

 case with the coager eel, which is supposed to 

 spawn in very deep water. It has never been 

 possible to observe the spawning of this fish in an 

 aquarium, for the death of the parent has always 

 taken place before the eggs were laid. There is 

 reason for the belief that this is the normal 

 occurrence in the sea also, except that the eggs 

 are, of course, deposited before the degenerative 

 changes leading to death (which have been ob- 

 served in specimens kept in tanks) are thoroughly 

 advanced. It is very probable that both conger 

 eel and fresh-water eel only spawn once in their 

 lifetimes, and that dseath soon follows the act of 

 breeding. 



