Growth rates of fishes are reflected in the 

 spacing of scale circuli: the faster the growth 

 rate, the wider the spacing between circuli. The 

 present findings, therefore, suggest that mark- 

 ing through the excision of adipose and right 

 pectoral fins in chinook salmon may have been 

 responsible for the slower growth rate of the 

 marked fish. Biologists, using various fin marks, 

 working on various species of fish, and experi- 

 menting under various conditions, have obtain- 

 ed contradictory results in this respect. Ricker 

 (1949), for instance, excised the pectoral, both 

 ventrals, or one pectoral and both ventrals of 

 the largemouth bass and found that recoveries 

 of these and unmarked fish indicated that the 

 marked fish were significantly smaller than the 

 unmarked ones. He believes that marking pos- 

 sibly affected the growth rate directly; how- 

 ever, when he marked 2-year-old bluegills, the 

 growth of marked and unmarked fish was the 

 same. Armstrong (1949) studied lake trout 

 fingerlings and found no appreciable difference 

 in length and weight between those that were 

 unmarked and those that had had the adipose 

 removed. Shetter (1951) also shows that re- 

 moval of the dorsal and adipose fins, right pec- 

 toral fin, or right pelvic fin from the fingerling 

 lake trout had no effect on the growth of the 

 marked fish but that removal of the left pectoral 

 appeared to have slowed the growth of the fish. 

 Again, on a study of growth of marked and 

 unmarked lake trout fingerlings in the presence 

 of predatory fish, Shetter (1952) found no 

 significant difference in the growth rate be- 

 tween marked and unmarked groups. 



In the Cultus Lake experiments on the sock- 

 eye salmon, Foerster (1934, 1936a, 1936b) 

 shows that unmarked smolts had a return rate 

 two and one-half times greater than marked 

 smolts that had both pelvics and adipose or 

 both pelvics and dorsal removed. He shows 

 further that this differential mortality was due 

 to the effect of marking upon marine survival, 

 since marking did not affect lake survival. No 

 data on fish length or scale growth were given, 

 however, so it is not known whether marking 

 did have an adverse effect on growth. 



The reasons for the apparent paradoxical 

 results on the effect of marking on the growth 

 rate of fish by various workers may be quite 



SCALES OF CHINOOK SALMON 



varied. The different results could be due to 

 different fins being clipped, different species be- 

 ing experimented on, different techniques being 

 applied, or different conditions under which the 

 experiments were made. 



SCALE GROWTH OF FALL CHINOOK 



SALMON, RELEASED BETWEEN 



MAY AND FEBRUARY 



At Little White Salmon Hatchery (fig. 1), 

 another Federal installation some 10 miles 

 downriver from the Spring Creek Hatchery, 

 the Bureau of Commercial Fisheries has con- 

 ducted further marking experiments on fall 

 Chinook salmon. Here, for the brood years 

 1956-58, young chinook salmon were reared for 

 various lengths of time and released at five dif- 

 ferent times of the year from May to February 

 (see under "Materials and Methods"). A dif- 

 ferent mark was applied for each release, so 

 that at return a marked fish could be positively 

 identified as to its date of release. 



The returns from these experiments offer 

 excellent scale samples for studying the growth 

 of nuclear zones. Fish released earliest (May) 

 should go to sea during the first year, and their 

 scales should show a typical ocean nucleus. 

 Those released latest (February of the follow- 

 ing year) spent the first winter in the hatchery, 

 and their scales should therefore have a stream 

 nucleus. Fish released between the above pe- 



FlGURE 7. — A scale of adult chinook salmon that was 

 released as a fingerling in May at the Little White 

 Salmon Hatchery (May 1957 release, 1959 return). 



173 



