28 FISHERIES OF ALASKA IN 1907. 



get the maximum value of the marking. It is probable, however, that 

 the use of a thermocautery in removing certain fins will make possible 

 the marking of fry soon after the absorption of the sac, if not earlier, 

 and will increase the speed and facility of the process. Experiments 

 already made indicate that this is a practical method of marking. 

 The Bureau of Fisheries intends to continue these experiments in 

 Alaska; and it is hoped that hatchery authorities or others will 

 make no identification marks on salmon without consultation with 

 the Bureau, in order to avoid confusion through adoption of the same 

 or similar marks. 



Regeneration of fins after cuts or injuries of course seriously affects 

 the value of marking experiments based on the cutting or removal of 

 fins. It is known that with some salmonoids, as brook trout, cutting 

 away a portion of some of the fins may be followed by a quite com- 

 plete regeneration. This has not been observed with the adipose. 

 With the Pacific salmons the evidence at present tends to show that 

 injuries and excisions of parts of the fins do not result in regeneration 

 to any marked degree, and especially a fin which is removed by cut- 

 ting deeply to its base will not renew itself at all. 



Return of salmon marked at Fortmann hatchery. — In August, 1903, 

 1,600 red salmon fry hatched at Fortmann hatchery were marked at 

 the age of about three months, by Mr. F. M. Chamberlain, of the 

 Bureau of Fisheries, and released in the Naha above Heckman Lake. 

 The mark consisted in the complete removal of both ventral fins by 

 means of small scissors. No adult redfish lacking the ventrals were 

 taken at Fortmann hatchery until the fall of 1906, and then but two 

 specimens. From 50 to 1 00 of such fish, however, were reported by the 

 superintendent of Yes Lake hatchery in the spawning run of 1906 at 

 Yes Lake. In 1907 no redfish lacking both ventrals were seen at Yes 

 Lake hatchery, but about a dozen were taken having but a single ven- 

 tral. At Fortmann hatchery the spawning run of 1907 yielded 13 red- 

 fish with both ventrals gone, and 1 with a single ventral. 



Specimens of the adult salmon lacking both ventrals were seen and 

 examined at Fortmann hatchery by the salmon agent. In most cases 

 there was scarcely a trace of the position of the missing fins, the skin 

 at the site of the base of this pair of fins being overgrown with scales 

 which indicated the former position of the fins only by their some- 

 what enlarged size and irregularity of arrangement. In one case very 

 short irregularly shaped stubs remained. The completeness of the 

 removal of these fins and the obliteration with the growth of the fish 

 of all but faint traces of the former existence of a pair of ventral fins 

 is somewhat remarkable. The identity, however, of these adult 

 salmon lacking ventrals with the individuals above referred to, 

 marked as fry in 1903 b}^ the excision of these fins, is very nearly con- 

 clusive, considering the infrequency of the absence of ventral fins 



