m. 646] 



FISH MIGRATION 



379 



stream, will journey into polluted water, spawn in places 

 where the eggs can not develop and in many cases, die 

 in such water themselves. 



Salmon are reputed to return to the lake-fed streams 

 where they were spawned and there is considerable evi- 

 dence that they are guided by temperature difference, 

 probably also by the current pressure, number of water- 

 falls, oxygen content and even by food. There is no ques- 

 tion (Meek, 1916), however, that salmon ascend streams 

 where no salmon could hitherto have spawned. 



The destruction of protecting forests, spoliation of 

 natural waterways and the utilization of streams by 

 manufacturers wishing to dispose of wastes are the fac- 

 tors which not only cause the death of fish embryos and 

 adults, but prevent the natural control of insect pests by 

 their destruction in the larval state. 



SUMMAKY 



1. Fundulus heteroclitiis is able to discriminate toxic 

 from non-toxic salts at a temperature and stream flow 

 the same as the control. 



2. Variations in temperature or in stream flow pro- 

 foundly influence the reactions and are more powerful 

 factors in the behavior of the fish than presence or ab- 

 sence of salinity. 



3. In the apparatus used, errors due to the notable re- 

 actions of fish to currents of water have been reduced 

 by presenting the control and experimental flows parallel 

 to each other. 



BIBLIOGRAPHY 



Calderwood, W. L. 



1907. The Life of the Salmon. London, 1907. 

 Chamberlain, F. M. 



1907. Some Obsen-ations on Salmon and Trout in Alaska. Eeport 

 and special papers for 1908. IT. S. Bureau of Fisheries, 

 Document 627. 

 Chidester, F. E. 



1916. A Biological Study of the More Important of the Fish Enemies 

 of the Salt Marsh Mosquitoes. Bull. N. J. Ag. Exp. Sta., 

 No. 300, pp. 1-16. 



