its trained response. Preliminary experiments showed the 

 yellowfin to be capable of hearing sounds as high as 2,000 

 cycles per second with a maximum sensitivity near 500 cycles 

 per second. For comparison, the highest pitch to which the 

 yellowfin responded (2,000 cycles per second) was consider- 

 ably lower than the maximum pitch of 15,000 to 20.000 cycles 

 per second for normal human ears. 



REWARD PUNISHMENT 

 OS- 



FACILITIES FOR UNDERWATER SOUND EXPERIMENTS 



\ / 



VISUAL STIMDLDS 

 \ 



(^S\ 



-REWARD (FOOD AREA! 

 -PATH OF FISH 



^PUNISHMENT I ELECTRIC SHOCK) 

 PATH OF FISH ^= 



—CHOICE POINT 



VISDAL STIMOIOS TORNEB OFF 



Figure 1. --Diagram of tank used in visual acuity 

 tests, showing testing procedure and behavior 

 of a trained fish. 



POOL DIAMETER 24 FT. ; 4 FT DEEP 



ROPE STRETCHED 

 ACROSS POOL 



FOOD TOSSED HERE 



PATH FOLLOWED BY FISH 



LOUDSPEAKER UNDER 

 WATER 



NET HANGING IN WATER 



OBSERVER S PLATFORM AND 

 EQUIPMENT HUT 



Figure 2. — Diagram of circular tank used to test 

 underwater sound perception in yellowfin, show- 

 ing testing procedure and behavior of a trained 

 fish. 



Since tunas swim constantly, knowledge of their swimming 

 behavior is essential to understanding their reactions. By 

 means of motion pictures, swimming speed and its relation to 

 tail-beat rate have been calculated for skipjack tuna, yellowfin 

 tuna, and Pacific bonito. All of the fish studied were about 

 1.2 feet infork length. Relative to tail-beat frequency, yellow- 

 fin tuna moved the fastest and Pacific bonito the slowest (fig. 3). 

 Maximum speeds observed in tunas that were feeding were 

 12 miles per hour for yellowfin, 15 for skipjack, and 8 for 

 Pacific bonito. Although these data demonstrate that scom- 

 brids can swim fast, they usually swim slowly; for example. 

 Pacific bonito slightly over a foot long usually swim about 

 2 miles per hour throughout the day. 



We recently observed that, contrary to popular belief, scom- 

 brids do engage in highly specific courtship behavior. Obser- 

 vations made on the behavior of Pacific bonito in conjunction 

 with Marineland of the Pacific at Palos Verdes, California, 



