Power Failare 



During a Z-week p>eriod In November 1952(, and occasion- 

 ally at other timesp the power supply to the inland and/or to the pumps 

 failedo Rather than waste valuable testing timcp pond experinnents 

 were conducted without the use of the pump„ Test material was in- 

 troduced by throwing it to the sxirface from the top of the tower when 

 the fish were distant from the attraction area. It was noted that a 

 material which was usually attractive to the fish was not sensed as 

 soon as when introduced by the punnpo Apparently it formed a layer 

 on the surface under which the fish could swim without being aware 

 of its presenceo When it was finally sensedj, it produced a reaction 

 which was stronger than usual^ probably because it was more con- 

 centrated than when introduced through the flow from the pump. 

 Again, the data would not be strictly comparable with those obtained 

 when the material was introduced in a normal fashiono 



Erratic Beha vior of the Fish 



In the tank under ideal control conditions the fish would 

 make full circles, keeping close to the walls and swimming at a 

 steady ratCo They would thus spend about one-third of their time in 

 the attraction area and each would average about 3 or 4 loops in a 

 2-mlnute periodo Howeverj ideal control conditions were not often 

 encounteredo Usually experiments were run when inspection of the 

 control data indicated fair regularity in movement and thus moderate 

 variance in the data, even though the times and counts might differ 

 considerably from the "idealo " A* timeSo particularly when one 

 tunny was the sole occupant of the tanks '* would circle for long 

 periods in either the upstream o* downstream end of the tank, giving 

 either zero or ma^tinnal times and counts o At times it would circle 

 for several successive minutes at one end ^gund would then repeat the 

 performance at the other endo At other tinaes it would swim back 

 and forth along one wallp entering the attraction airea either occasion<>- 

 ally or not at all. When behavior patterns such as these were en- 

 countereds testing was usually abandonedo with consequent loss of 

 tinneo Occasionally^ in desperationp the material was iniroduced 

 undei such conditions, in the hope that the fish would sense it and 

 show some response even though the data would not be comparable 

 with those obtained with nnore nearly normal behavior. When two 

 fish were present in the tanko even if one was not yet established^ 

 the pattern of movennent was more uniform and usually yielded con- 

 trol conditions which did not depart excessively from the ideal. 



In the pondj the laTge black yellowfin were more con- 

 spicnous and swam more slowly than the small blue-^green tunny, 



17 



