SALMON AND TROUT— SCHULTZ 369 



A review of the literature describing the nest-building activities of 

 salmon and trout indicates that practically all the older accounts 

 have confused it with the spawning act, the latter an entirely different 

 behavior. The following authors, among others, have given the same 

 interpretation to the nest-building act as described above: White 

 (1930, pp. 103-107) on eastern brook trout; Greeley (1932, pp. 242- 

 243) on brook, brown, and rainbow trout; Hazzard (1932, p. 345) on 

 eastern brook trout; Schultz and Students (1935, pp. 71-72) on land- 

 locked sockeye salmon. 



The process of nest building, the most obvious activity over the 

 nest, is done mostly by the females, although now and then certain 

 males flex their bodies three to five times, while other males never 

 participate in the construction of the nest. Usually during the 2 to 4 

 seconds that it takes the female to flex her body for purposes of dis- 

 turbing and hfting the gravel so that the current carries it downstream, 

 the male, if present, stands by inactively near the lower part of the 

 nest. The time that it takes to construct a single nest-pit varies 

 considerably with the individual, taking but a few hours or a few days. 



In the case of breeding salmon and trout, the careful observer has 

 little difficulty in distinguishing the two sexes, because the breeding 

 male is usually more highly colored than the female, and his body is 

 compressed (sides flattened), that of the female more rounded. Often 

 the snout is somewhat arched in the male trout and definitely hooked 

 (pi. 1, fig. 1) in the male of Pacific salmon; the female's snout is normal. 

 Experienced fish-culturists are able to tell the sex of spawning salm- 

 onids by feeling of them with their hands, the males having on the 

 underside of the abdomen two hard ridges which are lacking in females. 



The completed nests of salmon and trout are saucerhke depressions 

 with a small mound of sand and gravel on the downstream side. Their 

 depth and size depend on the size of the individual that constructs the 

 nest, and their shape on the rate of flow of the water over the nest. 

 Nearly round depressions occur in slowly moving water and oblong-oval 

 nests where the current is rapid. A fish about a foot long builds a 

 nest from 2 to 4 inches deep, depending on the type of stream bottom. 

 In moderately flowing water the width of the nest is one or two times 

 the length of the owner, and the length of the nest is two or three 

 times that of the female which excavated it. The mound of sand and 

 gravel at the lower end of the nest Hes from 1 to 3 inches above the 

 average level of the stream bottom and extends downstream below the 

 depression 2 or 3 feet. Several of these nests, or redds, may occur in 

 the same riffle of a stream. In the case of large king salmon, a single 

 nest may occupy several square yards of the stream bottom. 



The nests are continually changing, because after the female deposits 

 a portion of her eggs, she covers them with gravel, and as she pro- 



