220 Fish Behavior and Angling 



enzymes are affected in their action by minute amounts of many sub- 

 stances may explain the wide range of compounds that possess odors (to 

 humans). The abihty of an animal (or human) to recognize faint odors 

 in the presence of a constant strong odor is explained by the rapid 

 reversability of inhibitory effects on enzymes of odors continuously ap- 

 plied at a constant level. The strong odor of a soy bean processing plant 

 (while not unpleasant to many people) does not obscure a weaker but 

 more delectable odor of broiling steak. 



There is no indication that the acuity of olfaction in fishes is any less 

 than that of terrestrial animals. 



Location of Taste Organs 



In many species, taste buds occur on the outer surface of the body as 

 well as in the mouth. This is often demonstrated by lowering a piece of 

 raw meat on a string into an aquarium so that it approaches the tail of 

 a black bullhead. The fish will immediately turn and grasp the meat. 

 Experiments have shown that taste buds are most abundant in the barbels 

 of the bullhead but lesser numbers are scattered over the surface of the 

 body and tail.""^ 



This wide distribution of taste buds is characteristic of fishes that 

 normally live in turbid waters such as bullheads, other catfishes, carp, 

 and some of the other fishes that live and feed on the bottom. Fishes 

 such as bass or sunfish ( Centrarchidae ) that feed primarily by sight have 

 less well developed and less widely distributed taste buds. However, 

 observations substantiate a general hypothesis that the outer surfaces of 

 most fishes are sensitive to a variety of mild chemical stimuli. 



Bullheads and other fishes that have taste organs scattered over the 

 outer surface of the body use their olfactory organs for locating food at 

 a distance.*^ Tests of bullheads with barbels removed (taste) and others 

 with olfactory tracts severed (odor perception) demonstrated that odor 

 perception was more important than taste in locating earthworms in a 

 cheesecloth sack. 



Olmsted '^' tested bullheads with many natural substances to determine 

 which ones proved stimulating to them. Using 30 pairs of fish throughout 

 a fairly long period of time he charted the number of bites made by 

 each pair during trials extending for one-half hour. Materials used for 

 testing the fish were graded by using an arbitrary scale from 100 to 0; 

 most stimulating materials were rated near 100 and lesser ones accord- 

 ingly lower. In these experiments he discovered that human saliva rated 

 below earthworms and liver, but was rather high in its over-all rating. 

 Thus the custom of "spitting on one's bait" is apparently more than a 

 superstition. 



