132 U. S. BUREAIT OF FTSHERTES. 



greater than is indicated by these figures, for in 1919 comparatively 

 few fish of larger size were taken out for mild curing, while in 1920 

 there Avere put up 145 tierces of mild-cured kings, with 800 pounds 

 to the tierce. These were all selected from the larger sizes and would 

 have materially diminished the number required per case if all had 

 been canned. 



During the early part of the fishing season the Idng salmon were 

 silvery in color, Avithout trace of red; the testes are small, hard, and 

 purplish in color; the eggs are always small, not more than half the 

 size Avhen mature. The snout of the males was then so little pro- 

 duced as to give no certain indication of sex. This condition con- 

 tinued during the greater part of June, near the latter end of which 

 the run indicated a decided falling off. But on June 29 a second 

 run appeared of small dimensions, and it was at once apparent that 

 these fish were further along in their development. The jaws of the 

 male were now somewhat prolonged and hooked, and the enlarged 

 teeth had begun to show. They were now reddish in color, and the 

 bellies were so thin that they were little valued for mild-cure pur- 

 poses. These changes were abrupt and coincided with the sudden 

 increase in the run. 



The natural enemies which left traces of their presence on the 

 entering salmon were the white whales, or belugas, and the lamprey 

 eels. Belugas Avere very much in evidence in the lower river chan- 

 nels during the latter part of the season, the size of their schools 

 increasing as the salmon were running more abundantly. Un- 

 doubtedly they Avere feeding on the salmon, and it is safe to assume 

 that they captured and devoured a very large proportion of those 

 on Avhich they succeeded in closing their jaws. But the number of 

 salmon Avhich appeared on the cannery floor bearing unmistakable 

 tooth marks of the beluga was surprising. The sides were scored 

 lengthAvise by widely spaced lines, Avhich usually described a gentle 

 curve, but were occasionally angulated. Evidently these salmon had 

 escaped from the A^ery jaws of their pursuers. 



Other marks which attracted universal attention and Avere usually 

 mistaken for hatchery brands were the scars made by the lamprey 

 eel. This slender eel-shaped animal has an oval sucker-shaped 

 mouth provided with rows of rasping teeth. By means of the sucker 

 mouth it attaches itself to the salmon and may rasp off the skin 

 and even deeper-lying tissues for food. A scar is left which often 

 reproduces Avith great fidelity the details of the mouth, with its 

 outer fringe of filaments and its inner groups of teeth, Avhich in 

 the scar often give the impression of printed characters. 



Such lamprey scars haA^e been occasionally observed in other 

 riA'ers, but ncA^er before in such abundance as on the Yukon. This 

 fact pro})ably stands related to the large lamprey run Avhich is 

 indigenous to this stream. They enter the mouth of the river in the 

 fall after the surface has frozen and run up under the ice, to the 

 under surface of Avhich they often attach themselves Avhen resting. 

 Although the run lasts but few hours at any locality, it is of enor- 

 mous dimensions and furnishes tons of food to those who dip them 

 up through holes cut in the ice. 



Like the salmon, the lampreys enter the river for purposes of 

 propagation, and all die after the eggs are laid. The young soon 



