Fishes of the Western North Atlantic 483 



bird. The energy to maintain them during their stream life when they return to spawn 

 and the resources for the development of either eggs or milt have been built up and 

 stored in their bodies during the feeding stage in salt water. 



Why Atlantic Salmon in fresh water so often rise freely to artificial flies has 

 been widely argued and still is. An experienced angler has suggested verbally that on 

 sighting the fly an occasional fish suffers an attack of temporary insanity; this ex- 

 planation is perhaps as satisfying as any other that has been proposed. 



Predators. Atlantic Salmon are preyed on throughout their life, in both stream 

 and sea, and this factor, probably as much as any other, is generally responsible for 

 the small percentage that survives to spawn (pp. 479, 480). Most of what we know 

 about this subject is confined to reports for fresh water; as Pyefinch has aptly observed 

 (jj6): "The depredations of birds and other fish in fresh or estuarine waters may be 

 impressive only because they are visible and are noticed, they may actually be much 

 less significant than the effects of other predators present, for example, in the sea." 

 The extent of predation today relative to that under primitive conditions is not known 

 {142; 143). 



Atlantic Salmon are probably preyed on throughout their range by one or another 

 of the predatory fish that cohabit the same waters. In fresh water, birds (mergansers, 

 cormorants, gulls, and herons) destroy significant numbers of young. In the Maritime 

 Provinces of Canada, mergansers (especially Mergus merganser^ and the belted king- 

 fisher {Megaceryle alcyoti) are often destructive; control of these in the Pollett River 

 (Petitcodiac R. system) is believed to have increased smolt production eightfold. Follow- 

 ing control of mergansers^* on the Northwest Miramichi (but not on the Dungarvon 

 which is also tributary to the Miramichi system and has a similar run of adults), 

 production of large parr increased more than fourfold {44). Mergansers are also serious 

 predators on young Atlantic Salmon in Sweden (pj). Salvelinus fontinalis (brook trout) 

 in America and Salmo trutta in Europe eat young Atlantic Salmon in the streams; 

 and in some areas eels reduce their number (^J: 15). 



In marine situations, both harbor seals and gray seals are reported as frequently 

 preying on Atlantic Salmon when these gather near river mouths. Indeed, depredations 

 by seals, chiefly gray seals, cause substantial losses to the fishermen who operate traps 

 and drift nets in the estuary of the Miramichi and within the mouth of the river (^7 : 

 28). Very little information is available about the predation that obviously must occur at 

 sea. Ten Salmon, 10—12 pounds each, are reported to have been found in the stomach of 

 a shark about 25 feet long, caught eight miles east by south of Peterhead, Scotland. 

 One has also been reported from the stomach of a shark taken in Greenland (p. 490). 



An inspection in both 1956 and 1957 of adults caught in the estuary of the Mira- 

 michi River, N. B., showed that 0.46 and 0.66 "/o, respectively, either had small living 

 lampreys attached to them or bore lamprey scars ; the corresponding figures for those 

 in fresh water in the Northwest Miramichi were 0.15 and 0.25 "/j; no fish were 

 found with large adult lampreys attached. These records indicate that lampreys are not 



15. White has also studied the feeding by mergansers on Salmon fry (jjp, T40, 142, 143). 



3«* 



