138 



BULLETIN OF THE BUREAU OF FISHERIES 



by the recapture of tagged fish, that the majority of salmon do so return year after 

 year, a thesis generally known as the "parent stream theory." However, since 

 marked fish have occasionally been retaken in strange rivers, as noted above, and 

 since odd salmon appear yearly in certain streams where none have been hatched for 

 many years — in the Merrimac, for instance — it is equally certain that the "parent 

 stream" theory does not always hold. Probably the truth of the matter is that 

 while the great bulk of the fish never strays far and thus readily returns to the 

 home stream, wanderers that chance to be in the physical state leadmg to maturity 

 when they come inshore in the spring enter any large unpolluted stream they 

 encounter, however far from home. 



Enemies. — No doubt when they first go to sea the smolts fall prey to any large 

 predaceous fish — they have, indeed, been found in the stomachs of pollock — but 

 after one or two years' sojourn in salt water salmon are so heavy and strong that 

 only fish as large as tuna, swordfish, or the larger sharks can menace them. Their 

 worst enemy is the harbor seal, which is a common denizen of the northeastern 

 coasts of the Gulf of Maine. 



Fig. 51. — Brook trout {Salvdinus fontinalis) 



48. Brook trout {Salvelinus fontinalis Mitchill) 



Sea trout; Salter 



Jordan and Evermann, 1895-1900, p. 506. 



Description. — Although brook trout vary widely in general form in different 

 streams, when taken in salt water they are usually salmonlike in shape — that is, 

 with stout bodies usually about one-fourth as deep as long and tapering gracefully 

 to a small head. Tlae nose of a trout, however, is blunter than that of a salmon, and 

 its head is longer in proportion, the total length of the fish (not coimting the caudal 

 fin) being about four and one-half times that of the head,^^ while its mouth (gaping 

 back of the eye) is relatively larger. The general arrangement of the fins, including 

 the " adipose," parallels that of the salmon, but the ventral fins stand under the mid- 

 dle of the dorsal — that is, they are farther forward in relation to the latter than in 

 its larger relative. All the fins, too, are relatively larger, particularly the ventrals. 

 As a rule the anal has one fewer ray (usually 8) , but the number of dorsal rays 

 .(about 11) is the same. The tail of the sea trout is less forked than that of a young 

 salmon of equal size. 



•' Some trout are even longer headed. 



