SALMON AND TROUT IN ALASKA. 13 



Another change with residence in the sea is a rapid increase in 

 proportional depth. This is most marked in the coho. Seven exam- 

 ples from the head of Naha Bay, May 31, length 98 to 117 mm., had 

 depth 4.6 to 5, while in four examples taken August 2, at the cannery 

 wharf, 154 to 210 mm. length, the depth is 3.75 to 4.4, which approaches 

 the normal depth of the adult fish with matured sex products (3.5 to 

 4 + ). 



DETAILED DESCRIPTIONS OF THE YOUNG. 



The following key will assist in the identification of small fingerlings. 

 In larger examples — as large fingerlings and yearlings — the specific 

 characters of the adult must be the main reliance. 



Key for Identification of Young Salmon and Trout Between 1 and 2 Inches 



IN Length. 



With adipose lin, large moutli, moderate dorsal fin, siphon-shaped stomach. 

 a. Anal fin long, at least 12 developed rays, the last of these much shorter than the 



first, giving the fin a straight or concave margin or outline Salmon. 



b. Showing no distinct parr marks. Back dark in dead examples gorbiischa. 



bb. Usually with distinct parr marks. 



c. Parr marks less distinct, mainly above lateral line, body comparatively 

 slender; gillrakers short, equal to less than 2 interspaces; eye small. 



keta. 

 cc. Parr marks more distinct, showing below lateral line; body rather slen- 

 der or deep; eye large. 

 d. Gillrakers long, ec^ual to or greater than 2 interspaces; body rather 



slender; parr marks tending to become circular nerka. 



dd. Gillrakers short; lx)dy deep; parr marks well defined bars. 



e. Parr marks narrower than interspaces, often orange coloration on 

 fins; branchiostegals and anal rays few, 13 or 14; anal with 



marginal stripes kisutch. 



ee. Parr marks wider than interspaces, branchiostegals and anal 



rays many, 15 to 16, anal not striped tschawytscha. 



aa. Anal fin short, fewer than 12 developed rays, the last not much shorter than 

 the first, the entire fin thus having a convex outline or margin, the height 



great in proportion to length of base Trout and Charr. 



b. Parr marks as bars, body compressed, depth earned well toward tail. .Trout. 



bb. Parr marks as roundish Vjlotches with mottling above and below, body less 



compressed, tapering rapidly toward tail Charr. 



The Humpback Salmon, Oncorhynchus gorbuscha (Walbaum). 



The humpback fry (pi. i, fig. 3) at the time of closure of the ventral walls average 

 about 35 to 36 mm. in total length. Depth, greatest just behind pectorals, 6 in length 

 (exclusive of caudal rays); in ill-nourished examples the slenderness becomes marked, 

 this usually quite notable in late migrants; head about 3.5; eye 2.5 in head; nose 

 round and blunt, tip of lower jaw scarcely reaching profile; contour in front of dor- 

 sal fin little arched; lunation of caudal slight; pectoral rounded, 2 or a little more in 

 head (measured from axil to tip of longest ray); longest ray of dorsal about 2.5 to 3; 

 longest ray of anal 3 to 3.75; greatest length of ventral equal to or somewhat greater 

 than gi-eatest height of anal; gillrakers long and close-set, about 5-13 developed, 

 longest equal to half diameter of pupil, and to the distance from first to fourth (3 

 interspaces) at upper end of lower limb. 



