PACIFIC SALMON 



61 



somewhat more precisely stated by Foer- 

 ster: ''The parent stream theory as ad- 

 vanced and substantiated by Gilbert (1914- 

 24), and Fraser (1920) and others requires 

 that each salmon under normal conditions 

 return to the area from which it came and 

 in which it was reared." This ''parent 

 stream theory" is phrased within much 

 narrower limits as the "parent tributary 

 theory." The objections to these theories 

 are numerous and serious from the scien- 

 tific point of view and I desire to call at- 

 tention to what I consider defects in this 

 interpretation. 



First of all the statement is in no sense an 

 explanation. The use of the term ' ' instinct ' ' 

 has long been criticized by students of animal 

 activities and its lack of meaning been so 

 clearly set forth that it is unnecessary here 

 to repeat the arguments advanced in the dis- 

 cussion. Well established evidences show 

 that the supposed return of the salmon is 

 not without its exceptions and further study 

 may be expected to show that specific fac- 

 tors determine the movements of that mi- 

 nority as well as those of the majority of the 

 fish. To overlook the need of finding an 

 explanation of these movements and to con- 

 tent oneself with a blind phrase leads in- 

 evitably to misunderstandings and also turns 

 attention aw^ay from the study of those en- 

 vironmental influences which are important 

 in work for the conservation of the species as 

 well as essential to the scientific interpreta- 

 tion of the salmon migration. 



I maintain unreservedly that the desig- 

 nation "parent stream" leads to misunder- 

 standings that are unfortunate. Some 

 salmon certainly wander into other streams ; 

 the degree to which the fish scatter has not 

 yet been determined. The difficulties in 

 the way of exercising control are very great 

 and conclusions reached are often colored 

 at least by the numerous assumptions intro- 

 duced into the argument. One series of 

 experiments deserve especial consideration 

 because of the larger degree of control over 

 the movements of the fish that was main- 

 tained; this is the work done by Foerster 

 at Cultus Lake, British Columbia (Foer- 

 ster, 1929, etc.). Here the construction of 



permanent control apparatus installed at 

 the outlet of a small lake and its constant 

 supervision have given precise data on the 

 departure of yearling sockeye and the return 

 of adults. Thus in 1927 the downstream 

 migrants numbered 249,700, of which 91,- 

 600 had been marked by excising the pelvic 

 fins. Of these 4,737 returned as adults in 

 1929 and 1930, among which 3,930 were 

 unmarked and 804 marked. The percentage 

 of return was 0.88 for marked fish and 2.49 

 for unmarked fish (Foerster, 1934: 352). 

 The discrepancy in the return might have 

 been due to some unfavorable effect of the 

 marking operation or to inwandering of un- 

 marked sockeye from other areas. The 

 young were liberated immediately after 

 marking and were closely observed ; neither 

 infection nor increased mortality was shown 

 and the group appeared lively and perfectly 

 normal on comparison with the unmarked 

 group. This clearly favors the second ex- 

 planation suggested. Foerster noted partic- 

 ularly that no marked sockeyes wandering to 

 other areas had been reported. He stated 

 further "It is felt that such straying . . . 

 is the result of some exceptional circum- 

 stance. . . , Only one situation [exists] 

 ... in which the return of sockeyes to the 

 parent stream may not take place, that is 

 where eggs have been transferred from one 

 spawning area for planting in another." 

 To me these conclusions appear too narrow. 

 Elsewhere Foerster states that this evidence 

 . . . must be accepted with reservations. 



When one considers the conditions on the 

 Pacific coast, the great distances involved, 

 the large number of streams sheltering sal- 

 mon, the hordes of fish swarming in, the 

 widely scattered spawning grounds, the 

 swarms of fishermen with different gear and 

 methods, the confusion and speed of mass 

 production in the canneries, lack of knowl- 

 edge and often of interest in competing in- 

 dustrial plants endeavoring to secure the 

 maximum catch and finished product in the 

 brief season with frequent interruptions 

 from unfavorable weather conditions, as 

 well as other difficulties, one may well 

 wonder that any marked fish are ever se- 

 cured from other points than at just such a 



