Figure 34.— Correlation between stage of maturation and contents of: (a) iron, (b) copper, (c) zinc in 

 the liver and gonad, and (d) the relationship between the amounts of crude fat and of iron and copper 

 in the liver, Auxis rochei (Suzuki and Morio 1947). 



schools is strong not only among the adults but also 

 among juveniles. Data collected during fishing opera- 

 tions suggest that individuals tend to school by size 

 because those caught are more or less of the same 

 length. The fish scatter when disturbed but soon school 

 again. In Japanese waters, A. thazard, which usually 

 school near the surface during morning and evening and 

 also during f>eriods of cloudy weather, do not form large 

 schools (Imamura 1949). But the formation of dense 

 schools appears to be quite common in other areas; for 

 example, Nakamura (1938) reported that dense schools 

 of Auxi-s migrate into coastal waters of Taiwan during 

 certain times of the year and Serventy (1941) observed 

 schools comp)osed of hundreds of Auxis in southwestern 

 Australia in the summer. In East African waters, 

 Wheeler and Ommanney (1953) observed schools com- 

 posed of 100 to 1,000 fish whereas Serventy described 

 those around the Seychelles as "large" but gave no es- 

 timate of the numbers involved. 



Schools nf A. thazard are known to mix with those of 

 A. rochei, other tunas, and tunalike fishes. In Hawaiian 

 waters, Auxis are occasionally found mixed with schools 



of kawakawa (Gosline and Brock 1960), and both A. 

 thazard and A rochei have been reported captured from 

 one school (Matsumoto 1960a). Similar observations 

 were made by Kishinouye (1915) of Auxis in Japanese 

 waters and by Jones (pers. commun. with Matsumoto in 

 1959) of those that occur in Indian waters. Imamura 

 (1949) observed that A. thazard in Japanese waters are 

 also found occasionally mixed with skipjack tuna. 



There also appears to be some evidence that A. rochei 

 schools distribute themselves throughout the water 

 column by size. Morita (1972), who studied the move- 

 ment of tagged A. rochei off Japan, indicated that small 

 fish usually school near the surface and move faster than 

 schools of large fish, which usually occupy the middle 

 and deeper layers of the water column. 



3.53 Responses to stimuli 



The importance of light in relation to the diurnal ac- 

 tivity of tunas has been discussed by Whitney (1969). 

 Experimental work on the activity of various tunas in 

 captivity showed that captive A. rochei is negatively 



39 



