in the raceway, one order of magnitude above 

 threshold was chosen. Nevertheless, Wisby 

 (1952) reported some avoidance at this concen- 

 tration. We did not, however, observe any avoid- 

 ance where the substance was metered into the 

 raceway. It should be noted that concentrations 

 at the delivery tube could be as high as 100 ppm 

 before mixing took place. But, since the sub- 

 stance was delivered immediately below the falls 

 caused by the separating dam, mixing was as- 

 sumed to be rapid and complete. 



Although fish were treated with very low con- 

 centrations of the morpholine, EEG responses 

 were not evident until 100 ppm was reached in 

 responsive fish. But, other workers have also 

 found a relative lack of sensitivity with electro- 

 physiological methods. Home-stream responses 

 disappeared with dilution of home-stream water 

 to 5% (Oshima, Hahn, and Gorbman, 1969b), 

 and Sutterlin and Sutterlin (1971), recording 

 from the olfactory epithelium of Atlantic salm- 

 on, Salmo salar, found no response to morpholine 

 at 0.9 ppm. Yet Wisby (1952) got clear behav- 

 ioral manifestations of perception at concentra- 

 tions of 10 ~® ppm. 



Acknowledgments 



Special thanks go to Ronald Poff and Jerry 

 Kryka of the Department of Natural Resources, 

 Wisconsin for providing fish and hatchery space. 



Literature Cited 



Fagerlund, U. H. M., J. R. McBride, M. Smith, and 



N. TOMLINSON. 



1963. Olfactory perception in migrating salmon. 

 III. Stimulants for adult sockeye salmon (Oncor- 

 hynchus nerka) in home stream waters. J. Fish. 

 Res. Board Can. 20:1457-1463. 

 Hara, T. J. 



1970. An electrophysiological basis for olfactory 

 discrimination in homing salmon: A review. J. 

 Fish. Res. Board Can. 27:565-586. 

 Hara, T. J., K. Ueda, and A. Gorbman. 



1965. Electroencephalographic studies of homing 

 salmon. Science (Wash., D.C.) 149:884-885. 



Hasler, A. D. 



1966. Underwater guideposts — homing of salmon. 

 Univ. Wis. Press, Madison, 155 p. 



Idler, D. R., J. R. McBride, R. E. E. Jonas, and 



N. Tomlinson. 



1961. Olfactory perception in migrating salmon. 

 II. Studies on a laboratory bio-assay for home- 

 stream water and mammalian repellent. Can. J. 

 Biochem. Physiol. 39:1575-1584. 

 Oshima, K., W. E. Hahn, and A. Gorbman. 



1969a. Olfactory discrimination of natural waters 

 by salmon. J. Fish. Res. Board Can. 26:2111- 

 2121. 

 1969b. Electroencephalographic olfactory respon- 

 ses in adult salmon to waters traversed in the 

 homing migration. J. Fish. Res. Board Can. 26: 

 2123-2133. 

 Peck, J. W. 



1970. Straying and reproduction of coho salmon, 

 Oncorhynchus kisutch, planted in a Lake Superior 

 tributary. Trans. Am. Fish. Soc. 99:591-595. 



Siegel, S. 



1956. Nonparametric statistics for the behavioral 

 sciences. McGraw-Hill, N.Y., 312 p. 

 Sutterlin, A. M., and N. Sutterlin, 



1971. Electrical responses of the olfactory epithe- 

 lium of Atlantic salmon (Salmo salar), J. Fish. 

 Res. Board Can. 28:565-572. 



Ueda, K., T. J. Hara, and A. Gorbman. 



1967. Electroencephalographic studies on olfactory 

 discrimination in adult spawning salmon. Comp. 

 Biochem. Physiol. 21:133-143. 

 Wisby, W. J. 



1952. Olfactory responses of fishes as related to 

 parent stream behavior. Ph.D. Thesis, Univ. 

 Wisconsin, Madison, 42 p. 



Andrew E, Dizon 



Southwest Fisheries Center 



National Marine Fisheries Service, NOAA 



P.O. Box 3830 



Honolulu, HI 96812 



Ross M. Horrall 



Marine Studies Program 

 University of Wisconsin 

 Madison, WI 53706 



Laboratory of Limnology 

 University of Wisconsin 

 Madison, WI 53706 



Arthur D. Hasler 



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