58 FISHEKIES OF ALASKA, 1908. 



marked fish with those returning, and in the spreading of the return 

 over three successive years and into other waters than the parent 

 stream, rather than in any demonstration of the numerical proportion 

 of fish returning and the consequent effect of similar plants on the 

 general salmon supply. Considering the indeterminate number of 

 incompletely identified salmon taken at Yes Lake in 1906 and sup- 

 posed to bear this mark, and the returns which have undoubtedly 

 occurred unobserved, it is not well to make much inference concerning 

 the size of the total return, save that the percentage given is certainly 

 a minimum. 



It is not improbable that the result of this marking experiment will 

 prolong itself into another season, and more individuals occur in the 

 run of 1900. 



EXAMINATION OF SALMON FOR NATURAL MARKS. 



The examination of salmon for marks, imperfections, and injuries 

 to the fins, or absence of fins, presumably from natural causes, referred 

 to in the report for 1907, has been continued. This examination is to 

 determine the extent to which natural marks may simulate artificial 

 ones. At a cannery on Nushagak Bay during June and July, 12,700 

 red salmon were examined with respect to all fins. All the fins are 

 subject to imperfections of one sort or another, the caudal showing 

 most. Fins entirely missing are rare. Of the number cited, onl}^ one 

 right and one left ventral, from different individuals, were completely 

 gone, and in no case was the pair of ventrals lacking, as in the artifi- 

 cially marked fish above described. The adipose fin, on the other hand, 

 was missing in 5 of the salmon, or 1 in about 2,500. Besides these, 6 

 adipose fins were injured or imperfect. In considering the return of 

 salmon marked by the removal of the adipose fin, it is evidently nec- 

 essary to deduct from the observed return a certain number repre- 

 senting the proportion of adipose fms naturally lost. The larger the 

 number of salmon examined in regions in which artificial marks have 

 not been made the more accurate will be the basis for whatever cor- 

 rection of this nature is necessary. Full data on this subject will be 

 published when the examinations are finished. 



Several so-called ''marks" were brought to attention during the 

 summer. Three of these were of the same general character — an ellipti- 

 cal or nearly circular mark with milled edge, dotted inside with spots 

 of more or less definite arrangement. These marks are suggestive of 

 the impression of a coin or other artificial die, and readily appeal to 

 the uninitiated as a hatchery mark, A few specimens turn up nearly 

 every year. They are the scars left by the suctorial mouth of the 

 lamprey, probably the common Pacific form (Entosphenus tridentatus) , 

 with whose oral cusps the impressions generally agree. These scars 



