10 



pools. If one of every three or four transferred fish 

 escaped recapture, the percentage of these fish 

 that actually returned to home pools was consid- 

 erably greater than the data indicate. 



b. At times, high water and turbidity reduced 

 efficiency of the electric seine below average. 



c. The number of times pools could be re- 

 checked was limited by practical considerations. 

 Chances of recovering returned fish would have 

 been increased with a larger number of rechecking 

 operations. Formation of ice on Jordan Creek put 

 an abrupt end to rechecking in November, 1950. 



d. Some transferred fish may have returned 

 to home pools and have been recovered without 

 being recognized. Circumstantial evidence was 

 found that indicated some transferred fish had lost 

 opercular tags. However, no fish was collected 

 that showed direct evidence of having recently lost 

 a tag, and several fish retained tags through 

 the winter. 



2. The mortality rate of the experimental fish 

 was not known. Undoubtedly, some fish suffered 

 natural deaths, and some may have been taken by 

 anglers or have died from injuries received while 

 being collected and tagged. However, the stream 

 was fished very little during the experimental 

 period, and there was no direct evidence of mortal- 

 ity from handling. 



3. The number of smallmouth bass used in each 

 experiment was small, mainly because a single pool 

 in such a small stream could not support many large 

 fish. Because of this situation, the response of 

 each fish was emphasized more than if a larger 

 sampling had been possible. 



In this study, the strength of the homing be- 

 havior and attachment to home pools was judged 

 by the percentage of transferred smallmouths that 

 returned to their home pools, the speed of their re- 

 turn, and the number of times individual fish 

 exhibited successive homing movements. Consid- 

 eration was given to a number of factors believed 

 to influence homing behavior in fish: direction of 

 movement (upstream or downstream), water level, 

 size offish, and available habitat. As the transfer 

 experiments were conducted only in the fall, the 

 influence of time of year was not measured. Con- 

 ceivably, different results might have been obtained 

 at other seasons. 



Of the 23 smallmouth bass used in Experiments 

 A, B, and C, 12 (52 per cent) displayed positive 

 homing responses. The direction a fish had to take 

 (upstream or downstream) to return to its home pool 

 did not appear to influence homing behavior. 



The effect of low water on homing behavior was 

 observed in 1951 when movement of transferred 



smallmouths was impeded by the shallowness of 

 the riffles in some sections of Jordan Creek. Ap- 

 parently, fish were unable or unwilling to navigate 

 the stream between the pool to which they had 

 been transferred and their home pool. Thompson 

 (1933) suggested that the random movements of the 

 fish he studied may have reflected in some degree 

 the effects of the drought prevailing at the time of 

 his investigation. His observations are worth 

 noting here, even though neither the types of 

 stream nor the species he studied are comparable 

 to those of the Jordan Creek experiments. To 

 what extent water levels different from those in 

 Jordan Creek at the time of the 1950 and 1951 ex- 

 periments might have modified the homing behavior 

 of the fish is a subject for speculation and further 

 investigation. 



Large fish displayed stronger homing tendencies 

 than small fish. Of the 11 smallmouths that failed 

 to return to the pools from which they had been 

 removed, 7 had not been taken previously in the 

 particular sections of the stream in which the pools 

 were located. This evidence may indicate that 

 some of the smallmouths in any pool may be only 

 temporary residents and therefore should not be 

 expected to return. The fact that five of these 

 seven fish were 9.0 inches or less in total length 

 suggests that the small immature fish tend to 

 wander more than larger ones. Of the eight small 

 bass used in the three experiments, only three were 

 recovered from pools assumed to be their home 

 pools. These three were the only bass of small 

 size that had been taken previously in the stream 

 sections from which they were transferred. 



The influence of size of fish is especially 

 evident in the results of Experiment A. No small- 

 mouths of less than 10 inches were used in this 

 experiment. Five of the seven smallmouths returned 

 at least once to their home pool. Of 13 transfers 

 made from this pool, 9 (69 per cent) were followed 

 by homing responses. This rate of return is 

 considerably higher than that for the combined 

 experiments, 55 per cent (17 returns from 31 

 transfers), table 2. 



Homing, as demonstrated in these experiments, 

 cannot be explained simply as a random locating 

 and claiming of suitable available territory. If it 

 could, the large domineering fish would have been 

 likely to establish new territories before returning 

 to their home pools, as most returning individuals 

 passed through many pools suitable for smallmouths 

 before reaching their home pools. These experi- 

 ments showed that the tendency to return to home 

 pools was stronger among these large fish than 

 among smaller individuals. 



