PACIFIC SALMON 



73 



acanthias (Lutz, 1930a and 1930b, and 

 Lutz and Wyman, 1932a) and on the bran- 

 chial vessels of Squalns acanthias and Nec- 

 turus maculostis (Lutz and Wyman, 1932b) 

 and cardiac inhibition by stimulating the 

 carotid "gland" of the frog (Meyer, 1927). 

 In reptiles and birds as well as in mammals 

 there are innervated structures developed 

 in connection with the third branchial-arch 

 artery and an innervated pressor-receptor 

 zone of the aorta. It is reasonable then to 

 conclude that fish do possess these recep- 

 tors in the regions of their gills. 



As early as 1915 Shelford and Powers 

 found the herring {Clupea pallasii) was 

 quite sensitive and responded to water with 

 gradients of carbon dioxide, of oxygena- 

 tion, of acidity, of fresh-salt water mix- 

 tures and of slight temperature differences, 

 and that the humpback salmon (Onco- 

 rhynchus gorhuscha) was sensitive to gra- 

 dients of fresh-salt water mixtures. These 

 observations were followed by others by 

 Powers (1921) who showed herring to be 

 quite sensitive to slight gradients of pH. 

 Powers at that time was well aware that pH 

 differences were indices of differences of 

 carbon dioxide tension, as is stated in the 

 body of the paper. And yet these two 

 papers were misunderstood because the 

 same species of fishes were found in wide 

 differences in pH. It has been stated 

 definitely (Powers, Rostorfer, Shipe and 

 Rostorfer, 1938) that "The carbon dioxide 

 tension is the effective factor and not the 

 pH of the water. The pH is incidental to 

 carbon dioxide tension and alkali reserve 

 of each natural water." The ineffective- 

 ness of pH as such had already been dis- 

 cussed by Powers (1930). At this point it 

 is interesting to note that chemical recep- 

 tors of the carotid bodies are not sensitive 

 to pH — acidity — but to carbon dioxide ten- 

 sion (Samaan and Stella, 1935, and Comroe 

 and Schmidt, 1937). Samaan and Stella 

 state that "The responses to variations of 

 carbon dioxide tension are very prompt. ' ' 



The fact that the alkali reserve of the 

 blood of a fish is adjusted to the carbon 

 dioxide tension of the water has been shown 

 in various papers bj- the author and col- 

 leagues, and in certain of these it has been 



shown that the pH of the blood is fairly 

 stable over wide ranges of carbon dioxide 

 tension of the water (Powers, 1922 ; Powers 

 and Logan, 1925; Powers, Hopkins and 

 Hickman, 1932; Powers, Rostorfer, Shipe 

 and Rostorfer, 1938, and Powers, Rostorfer 

 and Rostorfer, 1939). Finally, it has been 

 shown, despite the fact fishes can adjust the 

 alkali reserve of their blood rapidly to a 

 definite carbon dioxide tension of the water 

 (Powers, 1938) that they become deranged 

 and die if the adjustment is back and forth 

 at too short intervals (Powers, 1937 and 

 1938; Powers and Rostorfer, 1937, and 

 Powers, Shields and Hickman, 1939). 



We have dwelt upon the physiology of 

 fishes since it is applicable to the salmon as 

 well as other fishes. The better the under- 

 standing of the physiology, the more likely 

 a true solution to the migratory movements 

 of the salmon will be- reached. 



There are certain well established facts 

 regarding migratory movements of the 

 salmon. These facts have been established 

 with regard to the (North American) Pa- 

 cific coast salmon by Gilbert and his asso- 

 ciates and others who have followed his 

 methods by checking returns of marked fry 

 and older tagged fish and by the study of 

 scales. The author of this paper will not 

 attempt to discuss the details of the find- 

 ings of these studies but will leave these to 

 those of this s.ymposium more competent to 

 follow the details. The author will point 

 out more pertinent facts as they relate to 

 his point of view. 



The so-called * ' parent stream theory ' ' has 

 almost become a proverb. Some of the 

 migratory movements of the salmon would 

 be fantastic (Gilbert, 1924) if there were 

 not absolute proof of the facts. All admit 

 that perhaps the majority of the salmon do 

 return to their parent stream. It is also 

 admitted that there is always a certain 

 amount of straying. Davidson (1937) 

 states, "Furthermore, I am not aware of 

 any biologists at the present time thor- 

 oughly familiar with the life histories of 

 the Pacific salmon who are of the opinion 

 that any of the species return to their par- 

 ent streams with unerring accuracy." We 

 all agree (Davidson, 1937) "... that the 



