(3) Sodakatauo ' mandara ) ( sabota ) ( rosoku ) ^uxis auoT" 



There are two species of s'odaka.tsuo„ the maruso'dakatsuo ^uxis meruT 

 and the hir as'gdr tkat s uo _ ^'axis hira^ yo Both like high temperatures and live 

 in the Kuroshio^ The marustrdaka tsuo is a coastal fish^ prefers the sv/ift 

 currents around promontories ^ and comes into the bays in schoolo. They 

 cone north on the Pacific coast as far as Shiriya Misaki in Aomori 

 Prefecture and also enter the Japan Sea„ They use their caudal fins to 

 maintain their position in swift currents and cl*7-erly capture food vfhich 

 comes drifting down to therao At morning and evening and in cloudy weather 

 they sometimes leave the swift currents in search of food and school at the 

 surf ac 3c 



The hiraso'daka.tsuo has the body more flattened laterally than the 

 preceding specieSs and is more of a pelagic fisho It lives around islands 

 and promontories s and its nattire is much like that of the sumagatsuoo They 

 do not fora large schools p but sometimes mingle with the true skipjacks and 

 in the summer they swim into the waters of the Sanriku area Northeastern 

 are^o Both speoies are warm v/ater fish and from their migrations it is 

 possible to judge the fluctuations in the Kuroshioo Around the autumn 

 equinox the schools which have been migrating north turn southward againo 

 Because of their structure these fish d'Alm in a straight linej their bodies 

 are torpedo-shaped^ They cannot make short turns and they are lacking in 

 buoyancyo They swim strongly and continuously and have finally become 

 adapted to living in currents so that their resting places are limited 

 to places which have swift currents „ They always live in clear water and 

 are very sensitive to any intrusion of freshwater running off from the 

 lando This species has wavy markings on the baok„ the snout is short, 

 and the eye is located far forward 



Paragraph 1 Ecology of the True Skipjack 



The true skipjack ^Sat suwonus pelamisJ 7 is the most pelagic of the 

 skipjacks o It r^-ms continually in schools out at sea and performs great 

 periodic migra*' iS north to the limits of the OyashiOo The skipjack 

 fishery in Japanese waters has grown up in dependence upon this species o 



Ip Spawr 1 ( areas of the true skipjack 



The skipjack ''s spawning grounds are in areas of suitable warm water 

 where ■'-here is plenty of food for the development of the young fisho They 

 spe->m, <4nd develop in the southern waters^ and when they reach their prime, 

 th';- become aware of the instincts proper to the skipjack and start on 

 t.' '- r long mieration north. In the spring and sunmer they pass through 

 J»-panese waters and about the time of the autumn equinox they return to the 

 southern seaso In this fashion they continue for many years to migrate 

 north and souths When they reach old age and no longer have the strength 

 and spirit to go norths some cf them find a suitable place along the path 

 of migration and '-ake up their residence on a reef or shoal^ becominp; the 

 so-called "shoal skipjacV". ^dle others leave the migratory schools^?-" 

 the migration begins ■• ;.heir lives quietly in the Sorith S»- 



17 



