224 Fish Behavior and Angling 



Brett and MacKinnon ^^ made a series of tests to explore the sense of 

 smell in migrating coho and spring salmon. When dilute solutions of 

 various chemicals were introduced in the path of salmon moving up a fish 

 ladder, they caused no significant change in migration rate. However, 

 a dilute rinse of mammalian skins had a distinct repellent action sug- 

 gesting that the salmon may have been conditioned against this odor. 



These experiments with salmon indicate that the olfactory organs are 

 very important in orientation and migration of these fishes. The long 

 migrations of salmon are necessary in order that the fish complete its life 

 cycle; therefore one might expect that sensory development of organs 

 useful in making the long journey might be more highly developed in 

 salmon than in fishes living a fairly localized existence. 



Odor as an Aid in Homing. Homing, home range, and territoriality of 

 fishes will be discussed later in Chapter 8. Displaced fishes find their way 

 back to home areas by using a combination of sensory organs. However, 

 Gunning ^^ was able to show that odor orientation was more important 

 than vision in the rapid return of a fish to its home area. In fact, blind 

 fishes with unimpaired olfactory organs were able to return to a home 

 range, after being displaced experimentally, as quickly and accurately 

 as control (normal) fishes. 



More detailed and technical information on the functioning of the 

 sensory organs of fishes may be found in the book "The Physiology of 

 Fishes," Vol. 2, edited by Margaret E. Brown.^^ 



TEMPERATURE PERCEPTION AND RESPONSES 



The body of a fish is almost uninsulated from the cold or warm water 

 surrounding it, presumably because fishes do not maintain a constant 

 body temperature. This does not mean that they are insensitive to 

 temperature changes or cannot be killed by high or low temperatures. 

 Fishes frequently expire through exposure when they are moved from 

 extremes of heat and cold within the north-south range of a species. For 

 example, red-ear sunfish transferred from northern Texas to central Illinois 

 lived during the summer but died over the first winter, in all probability 

 from the cold. There is also a likelihood that bluegills from northern 

 Michigan would die from high water temperatures if moved to southern 

 Alabama or Georgia. However, through a series of transplants, gambusia, 

 a live-bearing top minnow indigenous to the southern United States, was 

 purposely moved northward from its normal range nearly 700 miles during 

 a period of about 20 years. This was accomplished in 4 or 5 stages: Off- 

 spring of the fishes that survived one or more winters at one stage were 

 in turn moved northward to the next stage until they were thriving in 



