218 BULLETIN OF THE BUREAU OF FISHERIES 



fish would have been in their ninth year, an age greater than tlie maximum attained 

 by sockeye salmon. Chambei'lain later observed fish with both ventrals lacking 

 and concluded that they were not of his marking.^ 



Another unsatisfactory mark, which has been used on several occasions on the 

 Columbia River, is the removal of a small piece of the caudal fin. In some cases 

 the tip of the dorsal lobe of the fin was removed, but more frequently a small 

 U-shaped piece was clipped out of the posterior margin of the fin. These marks 

 are unsatisfactory for two reasons: First, because the caudal fin frequently is muti- 

 lated in nature; and second, because, as mentioned above, fin rays regenerate rapidly 

 unless they are removed at their base. Supposed marks of this nature are brought 

 to the attention of the authors every season. They have been found on all species 

 of salmon and on the steelhead and cutthroat trout, although no such marks have 

 been applied to any but chinook sahnon. The condition observed most frequently is a 

 U or V shaped notch in the posterior margin of the fin. The rays that form the margm 

 of the notch generally are bent and distorted. Occasionally tlie distortion extends for 

 a considerable distance back into the fin, indicating that the notch was much larger 

 originally and that it was reduced by regeneration. Some of these supposed marks 

 obviously are the results of attacks by seals or sea lions. In some cases this is indi- 

 cated clearly by tooth marks, which can be traced across the side of the fish and 

 across the caudal fin to the apex of the notch. 



By marldng two or more widely separated fins in the present series of experiments 

 we believe we have obviated, as nearly as may be, the possiblity of having our marks 

 dupHcated by accidental means. The validity of every record of recovery of marked 

 fish has been checked by careful examination of the scars resulting from the removal 

 of the fins. Where there has been any question as to the validity of the marks the 

 records have been excluded. The scars, particularly those resulting from the removal 

 of the ventral fins, have been found to be so uniform and characteristic in appearance 

 as to make it seem almost impossible for them to be produced by other means than 

 amputation with a clean-cuttmg instrument. It is not hard to conceive that an 

 occasional fish might lose one or more of its fins as the result of attack by enemies, 

 or that among the many thousands of salmon there might be a few that would fail 

 to have the full quota of fins at bu-th; but it is difficult to imagine how such loss 

 could result in scars that indicate the removal of the fins at their very insertion and 

 leave the surrounding tissue and pelvic bones normal. It is inconceivable, also, 

 that such improbable accidental loss could occur to hundreds of salmon at the same 

 time and in just such a manner as to confoimd the results of our experiments. 

 Fm-thermore, the evidence of scale readings entirely corroborates the evidence 

 of our marks — a most unlikely occurrence if the scars were the result of accidental 

 mutilation. 



Marsh and Cobb (1908), in discussing the returns from Chamberlain's experi- 

 ments, describe the "scars" of the two ventral fins as follows: "In most cases there 

 was scarcely a trace of the missing fins, the skiu at the site of the base of this pair of 

 fins being overgrown with scales." In no case in the present series of experiments 

 have the scars resulting from the removal of the ventral fins been overgrown with 



" Cliumberlain and Bower, 1913, pp. 29-31. 



