THE FISHES OF ALASKA. 



249 



30. Oncorhynchus kisutch (Walbaum). Silrcr Salmon; Coho. (PI. xxxi and xxxii.) 



The coho i.s common in Southeast Alaska and as far north at least as Karluk. It also occurs in Bristol 

 Bay and probably in the Yukon. Nelson (18S7) records it from St. Michael and Norton Sound, where 

 he says the run in the streams begins about September 1. The first examples seen by us were caught 

 June 19, by trolling in the outer harbor at Nanaimo. After that date the fish was seen at most of the 

 canneries visited, being in greatest abundance, however, at those canneries visited late in August. 



Dr. Gilbert, speaking of this species at Unalaska, says: 



Two young were seined at Unalaska, June 16, 1890, the smaller of which, 190 mm. long, shows 

 very conspicuous parr-marks. These have disappeared in the larger specimen, 225 mm. long, which 

 has also a.ssumed more the proportions and appearance of the adult. In this specimen the spots are 

 more distinct than in the atlult, being large, well defined, and close-set on head, back and dorsal fin, 

 and the caudal fin is very indistinctly marked, the faint spots being confined to the outer rays of both 

 lobes. It is a male with the testes so well de\-eloped as to make it very probable that it would have 

 sought the spawning-grounds within a few months. Three .smaller specimens were taken in Herendeen 

 Bay July 5. The smallest of these is 145 mm., the largest 185 mm. long. The distal half of the dorsal 

 fin is black with the exception of the last two rays, which are entirely white. 



Mr. Rutter found the young common in sloughs along the edge of Karluk River near its source 

 May 22. Forty-one specimens taken on that date were each about 1.25 inches long, 16 others were 2.8 

 to 6 inches long. He gives the life color of a 6-inch specimen taken from the ocean June IS as follows: 



Back olive brown thickly spotted with black; dorsal dusky except that the last ray is pale; tip 

 of caudal dusky; the dusky portion greater on lobes; a specimen photographed to-day has distinct parr- 

 marks; pectoral yellowish; caudal also }-ellowish by transmitted light; iris somewhat golden. 



Under normal conditions the coho is the last salmon to appear, the run in Southeast Alaska usually 

 not beginning until after all the other species have gone. 



The run of cohos at Nushagak is usually not large during the canning season, but is said to be 

 larger later in the year. In Nelson Lagoon (Bristol Bay) there is a run in August, too late to be utilized 

 by the canneries. There is said to be a good run in Bear River (Bristol Bay) in July and August. The 

 species seems to be fairly abundant among the Aleutian Islands, as evidenced by the fact that, in Sep- 

 tember, 1906, a Japanese vessel secured 1,.500 fish about .\ttu Island; and it is stated that other vessels 

 secured about the same number earlier in the season. At Alitak (Kodiak Island) the run begins about 

 the latter part of August; it is chiefly in Silver Salmon Bay. The species occurs also at Yakutat. At 

 Dundas Bay the first coho seen in 1906 appeared on July 1. 



In size, the coho ranks third among the Pacific salmon. The following table gives the lengths 

 and weights of 556 individuals, representing 11 different localities. The longest fish was 33 inches in 

 total length, the shortest, 20.75 inches; the heaviest weighed 15 pounds, the lightest, 3 pounds. The 

 average length of the males (235) was 28.29 inches, of the females (321), 27.53 inches. The average 

 weight of the males was 9.03 pounds, of the females, 8.86 pounds. 



Lengths akd Weights op Coho Salmon. 



Locality. 



Nichols Bay.. I 



Hessa Inlet 



Home Bay, Klawak. 



Num- 

 ber ; 

 exam- ] 

 lined. I 



Shipley Bay 



Hunter Bay (Nutkwa 

 Stream) 



YaliUtat 



Pillar Bay ! 



Nanaimo 



Karta Bay... 

 Dundas Bay. 



Chignik Bay. 



26 

 78 

 44 i 



Length. 



Maxi- 

 mum. 



Inches. 

 31.75 

 30.75 

 33.00 

 30.60 

 30.50 

 29.75 

 31.00 

 29.75 

 30.50 

 29.50 

 30.00 

 29.00 

 33.00 

 29.00 

 22.50 

 20.50 



Mini- 

 mum. 



Inches. 

 26.50 

 24.50 

 26.00 

 20.75 

 25 50 

 24.25 

 24.25 

 22.75 

 24,00 

 23.25 

 23.00 

 24.00 

 27.00 

 20.75 

 21.50 

 26. SO 



Average. 



Inches. 

 29.14 

 2S.29 

 29.59 

 27.99 

 28.64 

 27.58 

 27.84 

 26.82 

 27.67 

 26.54 

 26. .56 

 27.50 

 29.75 

 27.58 

 22.00 

 26.50 

 27.17 

 27.25 

 29.63 

 28.50 



Weight. 



Maxi- 

 mum. 



Mini- 

 mum. 



Lbs. 

 14.00 

 12.25 

 14.00 

 12.00 

 16.00 

 11.50 

 13.00 

 11.00 

 12.00 

 11.50 

 12.00 

 11.00 

 11.75 

 8.25 

 4.25 

 7.00 



Lbs. 

 6.00 

 5.00 

 7.50 

 4.00 

 6.00 

 4.00 

 6.00 

 5.00 

 5.00 

 5.00 

 4.00 

 6.00 

 8.25 

 7.00 

 3.00 

 7.00 



Average. 



Lbs. 



10.71 

 9.55 



10.97 

 9.85 

 9.95 

 8.70 

 8.35 

 7.06 

 9.11 

 8.31 

 7.88 

 8.67 

 9.62 

 7.58 

 3.63 

 7.00 

 8.00 

 8. .50 



12.50 



10.00 



Total 

 num- 

 ber 

 exam- 

 ined. 



104 

 100 

 100 

 105 

 100 



Average 

 length. 



Inches. 

 28.50 



28.69 



27.95 



27.34 



27.10 



26. 81 



28.82 



27.13 

 29. 06 



-■Vverage 

 weight. 



9. 84 

 10.34 

 9.14 

 8.02 

 8.71 

 8.09 

 8.75 



8.13 

 11.25 



