Figure 2.--Personnel of the Idaho Fish and Game Depart- 

 ment attaching disk tag to Chinook salmon. Fish is partially 

 submerged in water supplied by hose in left foreground. 

 Canvas cover over head of salmon helps quiet it during 

 taggmg. 



Petersen Disk Tag 



Tagging and release of disk-tagged fish dif- 

 fered in certain details during the 3 years of 

 the study. In 1960, fish were tagged at the 

 Oxbow trap and transported directly to release 

 sites in the river or the reservoir. In 1961, 

 untagged fish were transported to the release 

 site and discharged into a holding pen ; individ- 

 ual fish were then removed, anesthetized, 

 tagged, and released at the site. In 1962. fish 

 were taken from the Oxbow trap in groups of 

 as many as 30, anesthetized en masse, tagged, 

 put in a tank truck with fresh water to re- 

 cover, hauled to the river or reservoir release 

 site, and discharged into an open-ended holding 

 pen. They swam over a submerged weir at 

 the open end of the pen to resume migi-ation. 

 Individuals that did not leave the pen in 24 

 hours were eliminated from the experiment. 



Releases of tagged and untagged fish in 1962 

 varied between migration periods. During the 

 early and late stages of migration, fish were 

 released daily for 6 successive days at a single 

 site. For example, tagged fish were released in 

 the Snake River on the first day of a week and 

 in the reservoir on the next day. On the third 

 day of the series, only untagged fish were re- 

 leased in the reservoir. This sequence was re- 



peated over the next 3 days. No tagging was 

 done on the seventh day, but fish captured in 

 the trap at Oxbow Dam were transported and 

 released in the reservoir by the Idaho Power 

 Company as part of their usual fish-passage 

 work. At the peak of migration (September 

 24 to October 14), tagged fish were released 

 daily at both sites for 5 days a week. No more 

 than 30 fish with Petersen tags were released 

 at either site on any day. (In this same period, 

 fin-clipped fish were released in the reservoir 

 along with untagged fish that were excess to 

 the tagging needs. ) On the other 2 days of the 

 week, only untagged fish were released in the 

 reservoir. 



Fin Clip 



Fish marked by an adipose fin clip were re- 

 leased at the reservoir site only in 1962. These 

 fish had been anesthetized and inspected during 

 selection for spawn taking at the Oxbow hatch- 

 ery but were not retained for that purpose. 

 They were fin clipped to differentiate them 

 from untagged fish that were released during 

 the early stage of the 1962 experiment (Sep- 

 tember 10-16), but most were released during 

 the peak stage of migration (September 24 to 

 October 14). 



Sonic Tag 



Each sonic tag, used in 1961-62, was fas- 

 tened by a metal clip or hog-ring which was 

 crimped into the flesh behind the dorsal fin. 

 The battery-powered tags emitted 132-kc. sig- 

 nals, detectable by receiving equipment within 

 a range of about 1 km. ; the operational life 

 was about 5 days. 



Salmon bearing sonic tags were released only 

 in the reservoir in 1961 and only in the Snake 

 River in 1962. In 1961, they were tagged at 

 the reservoir release site and allowed to resume 

 their migration from an open-ended holding 

 pen. In 1962, the fish were tagged in groups 

 of 6 to 14 at the Oxbow trap, coincident with 

 the Petersen-disk tagging, and transported with 

 the other tagged fish to an open-ended holding 

 pen at the Snake River release site. 



The sonic tags enabled us to obtain detailed 



38 



U.S. FISH AND WILDLIFE SERVICE 



