98 



THE MIGRATION AND CONSERVATION OF SALMON 



eneed the action of these fish. The sulphur 

 affects the fish apparently disagreeably. 

 When the water became pure and clear and 

 had no sulphur taste, then the sockeye en- 

 tered and tried their best to utilize that 

 stream as a spawning ground or as an ac- 

 cess to a lake spawning ground which did 

 not exist. 



Another temperature influence may be 

 well illustrated by observations on Baker 

 Lake and lakes well up on the Copper River 

 in Alaska, in both of which places the 

 spawning grounds chosen were exclusively 

 in spring-fed gravel found only at certain 

 points in the lake. One could go round the 

 lake with a thermometer in the water and 

 by observation could determine that there 

 was also an inflow of cold water at places 

 where the fish were spawning and not at 

 any other point, in those lakes at least. Se- 

 lection of a spawning ground was specifi- 

 cally in spring-fed gravel with outflowing 

 colder water. 



I have said that the adult fish move con- 

 stantly upward against the current. After 

 hunting for many years I found an excep- 

 tion to that which is worth stating. Be- 

 tween the hydroelectric plant on the Baker 

 and the dam is a stretch cut off by a fence 

 from the river channel below the plant. 

 Water flows down this stretch only when 

 it is wasted from above the dam. On one 

 occasion in the morning sockeye were found 

 in the bay above the fence trying to get up 

 the stream. They had gone under the fence 

 and were working their way up the rapids 

 to the dam. At a particular moment they 

 stopped, evidently dissatisfied, and began 

 suddenly to back off downstream. That 

 moment was just when the flow of water 

 over the dam stopped and the water level in 

 the rapids began to drop rapidly. The fish 

 stopped in the first deep pool they reached 

 and then as the water became a little shal- 

 lower they turned about and darted into 

 the next deep pool, but stopped, again 

 pointing upstream. As the water kept sink- 

 ing they made another dash in the same 

 way. Thus they were forced to continue 

 until they got to the deep pools below the 

 fence and only then stopped their down- 

 stream movement. 



My work has been almost entirely de- 

 voted to observing the actual movements of 

 the fish. I have studied the living fish days 

 and weeks to see how they behaved and I 

 have found no exceptions to these behaviors. 

 I am convinced myself that there is no such 

 thing as a mysterious influence as you call 

 it. I believe the fish are guided by condi- 

 tional reflexes. 



Dr. Rich. Do you think that this condi- 

 tioning can be accomplished in the early 

 life of the fish and carried? 



Dr. Ward. The conditioning can not be 

 done in the early life of the individual fish. 

 At the start of the period of sexual devel- 

 opment the activity of the fish changes di- 

 rectly from one of seeking food to seeking 

 conditions for reproduction. 



Dr. Rich. The essential point at issue 

 between Dr. Ward and myself has been 

 whether or not the fish return to their par- 

 ent tributary. There is a very large body 

 of experimental evidence to which I re- 

 ferred yesterday, that supports the view 

 that they do return. Anything that does 

 not fit in with that theory and with the facts 

 upon which the theory is based would have 

 to stand a very careful scrutiny. I would 

 ask for evidence contrary to that theory. 



Dr. Ward. I am not dealing with the 

 migrations in the sea, but I simply say that 

 the fish carry out their activities under the 

 influence of the environmental conditions. 



Dr. Rich. The return of the fish is di- 

 rected. Those of us who accept the home 

 stream and the home tributary theory, only 

 say that these environmental conditions 

 are the guides that in some way direct the 

 fish back. They go back. So far as the Pa- 

 cific salmon are concerned I am thoroughly 

 convinced that they do return to their home 

 stream and home tributary, and any theory 

 that does not fit in with that fact is open 

 to suspicion. 



Dr. Ward. A long time ago I asked in 

 discussion : What do you mean by the home 

 stream? If fish eggs are taken to a hatch- 

 ery and hatched and the young fish are 

 planted there, is that their home stream? 

 Outside the Baker River, i.e., in other 

 branches of the Skagit River, which look 

 like better spawning grounds than Baker 



