536 Memoir Sears Foundation for Marine Research 



would ordinarily remain in salt water, or at least in brackish water, they may return 

 temporarily to the stream mouth in pursuit of prey. Thus they re-enter the Fox 

 Island River, Newfoundland, in June and July, apparently to feed on the smelt 

 that spawn there, and return to the sea afterwards with the spent smelt ;2' also. Brook 

 Trout that have wintered in the sea revisit the Dunk River on the north shore of 

 Prince Edward Island in April, or a little afterwards, when the smelt enter the brooks 

 to spawn. ^^ 



Relation to Temperature. S.fontinalis feed most actively at temperatures of about 

 45°-65°F (7.2°-! 8.3° C); they do not thrive in water warmer than 68° F (20° C); 

 and they cannot long survive a temperature higher than about 70° F (2i.i°C) unless 

 the water is especially well aerated, when they can withstand 75° F (23.9° C) for a short 

 time. At the other extreme, they become inactive and refuse food if the temperature 

 falls much below about 38°F (2°C), which accords with White's observation that the 

 annual downstream movement oi fontinalis in the Moser River system is interrupted 

 if the temperature of the water temporarily falls that low (^y6: 260, fig. 2). 



Food. The diet of the fingerling Salters is the same while they are in fresh water as 

 that of their nonmigratory relatives; i. e. chiefly the aquatic stages of various insects 

 such as midges (chironomids), caddis flies (Trichoptera), May flies (Ephemeridae), and 

 black flies (Simulidae). They also eat snails and freshwater gammarid crustaceans if 

 these are available, besides terrestrial insects that may fall into the water. 



During their sojourn in brackish or salt water they feed chiefly on small fishes, 

 of whatever kinds are the most easily available locally, or on small crustaceans. Ever- 

 mann, for example, found Brook Trout in the tidal waters of Casco Bay, Maine, "gorged 

 with young eels of the translucent stage" (20: 105). The diet list reported for Salters of 

 the Moser River includes young eels, young hake (Urophycis), young searavens {Henii- 

 tripterus), killifishes {Fundulus), rock eels (Pho/is), sticklebacks (Gasterosteus), and ale- 

 wife fry (Pomolobus); and smelts {Osmerus) as well as silversides (Menidia) have been 

 reported as being eaten by them at Prince Edward Island {y^: 184; yy: 472). They 

 feed greedily on decapod shrimps, amphipods, and isopods, which, together with 

 Fundulus, are their chief food in the Cape Cod region. Weed {y2: 130) has written 

 that Salters caught in the bays of Labrador had their stomachs crammed with beach 

 fleas (Gammarus). Others had been feeding on the tiny swimming larvae of the rock 

 crab {Cancer). And they have been found gorged with sea worms {Nereis) at Prince 

 Edward Island. 



They eat very little, if anything, however, after they re-enter fresh water, probably 

 because of the scarcity there of prey of the sizes to which they have become accustomed 

 in salt water. And it is likely that such of the spent fish as winter in fresh water (p. 534) 

 continue on starvation rations, if they feed at all, until they move down again to the 

 head of tide in the spring. 



Predators and Parasites. The smaller Salters are preyed upon, no doubt, by the 

 larger predaceous fishes, such as eels, striped bass {Roccus saxatilis), pollock {Pollachius 



29. Information contributed by W. P.Templeman. 30. Information contributed by P. S. Martin. 



