80 



THE MIGRATION AND CONSERVATION OF SALMON 



and lakes and coastal waters in which these 

 salmon have developed natural runs, have 

 in every case been similar to the com- 

 ponents of the waters frequented by the 

 salmon in their native range. On the other 

 hand, the environmental components of the 

 foreign waters in which these salmon have 

 failed to develop natural runs have dif- 

 fered from those of the waters native to 

 the salmon." (Davidson and Hutchinson, 

 1938.) 



Aside from the fact that environmen- 

 tal conditions must be favorable three 

 other facts are outstanding. First, certain 

 streams in South Island, New Zealand, have 

 been frequently stocked with 0. tscha- 

 wytscha (chinook, quinnat or king) but 

 have never developed natural runs. This 

 is also true of North Island in which no 

 natural runs have developed. Second, 

 "Not a single individual of the quinnat 

 species has ever been planted in a Canter- 

 bury stream, yet the Canterbury rivers now 

 provide the best quinnat fishing in the 

 Dominion, the species having migrated to 

 their mouths from the Waitaki where the 

 original fry were planted. ' ' Third, the red 

 salmon ' * eggs were imported in 1902 ..." 

 " 'a number (red salmon) exist in Lake 

 Chan, having acquired a land locked habit. 

 These fish run up creeks at the head of the 

 lake and spawn there every season (year) 

 in March and April'." 



In South Island, New Zealand, we have 

 (1) streams being stocked without produc- 

 ing runs, (2) an adopted parent stream and 

 (3) red salmon becoming land locked after 

 being planted and not developing natural 

 runs. 



The first proves that if the environmen- 

 tal conditions are not right the salmon will 

 not return (stray) to the stream of its 

 origin. The second proves that salmon, 

 provided the proper gradient is present 

 will move to a stream regardless of the 

 fact that neither it nor any ancestor has 

 ever visited or originated in the stream. 

 As to the land locking of the red salmon. 

 Professor Ward (1932) has given the best 

 and perhaps the only explanation. 



Environmental factors cause the salmon 



to migrate to the sea. Response to environ- 

 mental factors in the case of the land locked 

 salmon holds them in a lake. It is a strik- 

 ing coincidence that there is no regular run 

 of salmon into a land locked salmon lake 

 and vice versa. Ward, from the first, has 

 attacked the problem of salmon migration 

 from the point of view that the salmon is 

 responding to environmental factors (Ward 

 1921, 1927, 1929, 1930 and 1932). His 

 observations are in agreement with those 

 of the author. The carbon dioxide tension 

 of the waters, which are agitated in their 

 rapid descent from the glacial snowfields, 

 are necessarily approximately in equilib- 

 rium with the carbon dioxide partial pres- 

 sure of the atmosphere. The temperature 

 of these waters is continuously being raised 

 by the heat of the summer sun (Dall, 1882). 

 The carbon dioxide solubility coefficient of 

 water is lowered with rise in temperature. 

 Hence, the liberation of carbon dioxide 

 from the water would always l^g behind 

 the rise of temperature. Therefore, at the 

 same time that the red salmon is moving 

 toward a lower temperature, it is also re- 

 sponding to a lower carbon dioxide tension 

 of the water. Figure 2 demonstrates the re- 

 lation of temperature to the carbon dioxide 

 solubility coefficient in distilled water. If 

 the temperature of the water were suddfenly 

 raised to 12° C. without loss of carboir diox- 

 ide, its carbon dioxide tension would sud- 

 denly be raised approximately 53 per cent. 

 Two questions now remain, first, to what 

 extent do salmon return to the stream 

 (spawning grounds) in which they actually 

 originated? And, second, why do the 

 salmon go out to sea? In connection with 

 the first it is maintained that each spawn- 

 ing ground gives rise to a definite race. 

 This is difficult to get around. However, 

 there has been much doubt as to the valid- 

 ity of these claims as to the distinctness of 

 races (Huntsman, 1937a and 1937b). Let 

 us examine once more the tagging experi- 

 ments carried on east of the Alaska Penin- 

 sula at points from Ikatan Bay to Unga 

 Island (Gilbert and Rich, 1927a), since the 

 returns from these experiments are unique 

 but analyzable. The salmon tagged are, 



