12 SALMON AND TROUT IN ALASKA. 



The humpback (0. gorhuscha) is unique among the salmons in never 

 developing the parr marks. It is usually entirely silvery in all the 

 young stages, and is the only one of the salmons whose young up to 

 some 6 inches in length, taken in fresh water, will show no parr marks 

 even under the scales. As possible exceptions to this must be noted 

 the dwarf sockeye, w^hose young are as yet unknown, and perhaps 

 small mature fishes returning for spawning. 



The fingerlings of the dog salmon (0. Iceta) have the parr marks 

 sometimes much reduced, and those readily disappear in poorly 

 preserved specimens. But where several examples are at hand the 

 greater average size in the younger stages, the slightly different out- 

 line, and the presence of these marks will always distinguish them 

 from the humpback. 



Of the four species of strongly marked fingerlings the steelhead 

 (Salmo gairdneri) may be recognized by its short anal, as noted above 

 for trout, and by its small size taken at the season of migration. 

 The sockeye (0. nerica), king {0. tscJiawytscha) , and coho (0. JcisutcJi), 

 being all for some time resident in fresh water and hence very vari- 

 able in size, require close inspection for trustworthy identification. 

 In general, in the fingerling stage the sockeye will be recognized by 

 its more slender and tapering form, and b}^ the more nearly circular 

 outline of the parr marks, though this latter does not always hold 

 true. The coho is usually distinguishable by the orange tints of the 

 lower fins (a character rarely absent) and by the white front margins 

 of both anal and dorsal, but especially by the falcation of the anal 

 through the extreme production or elongation of the first developed 

 rays. The king, very similar to the coho in general outhne, does not 

 exhibit tliis extreme form of the anal, and in the specimens examined 

 from the Karluk River the parr marks are larger and the marking of 

 the back much more notable. In a careful examination the sockeye 

 can almost always be identified by the greater length and number of 

 the giUrakers, and the king by the greater number of branchiostegal 

 and anal fui rays. (See detailed descriptions following.) 



In salt water the parr marks are rapidly covered by the bril- 

 hancy of the silver, so that, except the king and coho, which are 

 spotted, aU the species soon become plain. It is not known when the 

 spots of the adult humpback first appear. Whether this obliteration 

 of the parr marks by the silver overcast is caused by the salt water 

 may be questioned, although in the trout, which are known to run 

 indifferently in salt and fresh water, the change is marked, fish from 

 salt water being much more silvery. I have taken one example of 

 sockeye yearling in Jordan Lake that seems almost as silvery as the 

 salt-water individuals of the same size, but it is entirely unlikely that 

 it had returned from the sea." 



a See under smolt, p. 10. Day, op. cit., p. 90. 



