FISHERIES OF ALASKA, 1908. 



57 



Temperature Record at Salmon Rack at Lake Aleknagik, Alaska, Summer 

 OP 1908, IN Fahrenheit Degrees — Continued. 



SALMON-MARKING EXPERIMENTS. 



Trials have been made with the thermocautery as a means of 

 removing or marking the fins of salmon fry shortly after the absorp- 

 tion of the sac, and the fry have been held and are still under obser- 

 vation. Since the chief question here is that of regeneration of the 

 lost parts, the final determination of the value of this means of mark- 

 ing must be awaited. At present the indications are favorable. 

 Extended trials have been made with a brand of the character of the 

 letter S, burned by means of a thermocautery into the skin of the fry 

 at the stage mentioned above. These marks do not persist even 

 when deeply burned and attempts to obtain in this way a mark for 

 salmon fry which shall be permanent in the adult are therefore fail- 

 ures. It does not follow from these results that such a brand of 

 proper size placed on older fish would not persist as a plain scar of 

 definite form; but the younger fry are the ones for which a practi- 

 cable mark is the present desideratum, since it is already demon- 

 strated that fingerlings may be successfully marked. Experiments 

 will be continued along the lines already begun. 



RETURN OF THE SALMON MARKED AT FORTMANN HATCHERY. 



In the 190S run at Fortmann and Yes Lake hatcheries 5 adult 

 redfish lacking both ventrals were taken at the former and 3 at the 

 latter. These are returns from the Chamberlain marks of the sum- 

 mer of 1903, both ventrals having been completely excised from 

 1,600 tliree-months old redfish fry. The return has covered three 

 successive seasons, 1906 to 1908, inclusive, and amounts now, count- 

 ing only certainly identified specimens, to 23 salmon, or 1.4 per cent 

 of the number marked and liberated. The importance of returns 

 from these marks lies in adding certainty to the identification of 



