During preliminary Tests 1 to ±0 the cruising speed was erratic 

 and the fish often approached the observer^ apparently expecting 

 foodo The cruising speed became more regular during Tests 11 to l6o 

 The marlin flesh preparation was then siphoned into the tanko There 

 was an initial increase m cruising speedy followed by a decrease., 

 during which time (Trials 18 and 19) the yellcwfm hesitated near the 

 inlet apparently sensing the substance. Following thiSj the cruising 

 speed increased againj and then gradually decreased^ The number of 

 passes across AB also increased during the siphoning period, indicat- 

 ing attraction. From these, and similar results in other experiments^ 

 it is concluded that the yellowfin, even though in poor condition^ was 

 attracted by the mar'lin flesh preparationo 



V, Asparagine and dol-Asparagine 



One yellowfin and five tunny were present in the tank during 

 several experiments with these chemicals o Solutions ranging from 

 Ool to loO percent vv-ere usedo As no reaction? whatever were observed^ 

 the results are not included here. It may be concluded that these 

 substances were not noticed by the tunao 



vi. Copper acetate 



The question arose as to whether copper acetate might be used to 

 repel sharks without repelling tuna during long-line fishing opera- 

 tionso It was suggested that some information on this point mi^t be 

 obtained by determining the reaction of tuna in captivity to this 

 che.Tiical, While it was not possible to compare the reactions of the 

 tuna to that of sharks^, it was possible to compare them with the react- 

 ions of a few manini and baitfish which were present in the tank. 



The following concentrations of copper acetate were used: Ool> 

 0,2^ 0„5s and loO percenta Fcr each expsrimentj 3 liters of these 

 solutions were siphoned into the tank at A, at Cj or at both A aid C 

 together i, with the solutions flowing down-streamo A part of the tank 

 was thus kept clear of the solutiono Stronger concentrations were 

 not used for fear of injuring cr killing the tunao liVhen siphoned in- 

 to the tankj the solutions vfere clearly visible from above as a bluish 

 cloud.. The actual concentration of copper acetate in this cloud was 

 not determined; it changed rapidly as the cloud diffused,, 



The behavior of the tuna was similar at all concentrations of the 

 solution and the reactions differed only in degree » The first fish to 

 exhibit reactions were the manini , They swam i;5)-stream and remained 

 near the seawater inlet for the duration of each experiment. The 

 baitfish also avoided the down-stream part of the tank into which the 

 solution was being siphoned,, In generalj the yellowfin and tunny 

 cruised around the cloud of copper acetate solution but did not enter 

 ito As the o'loud diffused^ both species kept to the up-stream part 



30 



