SCIARROTTA and NELSON: DIEL BEHAVIOR OF HI. IK SHARK 



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FIGURE 4. — Data from two individual trackings of blue sharks typical of the late June to early October period. Top, shark positions at 

 approximately 0.5-h intervals. Bottom, telemetered sensor data. Note the absence of shoreward movement, the increased swimming 

 speed and depth at night (left), and the greater frequency of sudden direction change, i.e., multiple-direction recordings, at night I right ). 



the day, e.g., on blacksmith, Chromis punctipinnis 

 (R. R. Given pers. commun.; D. R. Nelson unpubl. 

 data) and on northern anchovy, Engraulis mordax 

 (T. C. Sciarrotta unpubl. data). 



The large size of the blue shark's eye suggests 

 adaptation to low light, as in general, nocturnal 

 fishes have relatively large eyes. However, large 

 eyes are also associated with moderately deep 



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