tank. This is, after all, wortny of attention as it tells realistically 

 of the improvement in handling methods obtained from the experience of a 

 few experiments. After the bait was thus safely got into the tanks, 

 the vessel cruised around Suruga Wan for a few hours, but about 8 hours 

 after the fish had been placed in the tanks the surface of the sea became 

 as calm as an oil slick and the boat's motion almost ceased. Circulation 

 in the old-style tank was insufficient and the free oxygen content fell 

 below the lethal level indicated by the basic experiments to as little 

 as 1»17 cc per liter with the result that many of the fish lifted their 

 snouts out of the. water , The new-style bait tank, on the other hand, in 

 readings taken at about the same time snowed tne extremely superior 

 value of 5,01 cc of i'ree oxygen per liter, 



The facts recorded above tell now much superior the new bait tank with 

 pump-type circulation is simply from the point of view of free oxygen. 



Death from Sudden Cnanges in Temperature 



Because fishes are poikilothermic animals, their body temperature 

 is easily affected by the temperature of the surrounding water, and is 

 raised or lowered by the conduction, radiation, and convection of heat, 

 but there are, of course, limits of hign and low temperature beyond 

 which they cannot exists These limiting values appear to vary quite a 

 bit with the species of fish, but it any rate if these limits are passed, 

 the fish cannot survive. For this reason tnere are quite a few cases 

 in which, when bait fish have been loaded into tne bait tanks and the 

 vessel has headed for the skipjack grounds of the South Seas, the vessel 

 has unwittingly entered a zone of water temperatures higher than the fish 

 can withstand and the precious bait has been killed off, or wnere fish 

 held in caotivitv in sheltered waters have been damaged by a sudden drop in 



T7TT 



water temperatures in the winter V - L - L 



In the case of the former, the plan of temporarily cooling the 

 sea-water in the bait-tanks and trying to get out of the danger zone has 

 been proposed by this Station already, and at the Taiwan Fisheries 

 Experiment Station they are already planning to put this into effect, but 

 the problem which naturally arises here, is to find out how high and how 

 low the lethal temperatures for bait fisn are and now they are affected by 

 sudden changes in water temperature.. 



The resistance of fisnes to high temperatures has been studied by 

 Day, 9) KnauthelO) , and Hath away J-l) while their resistance to low tempera- 

 tures has been reported on by Dutrochet}2) Heath}3) and Carter^) <, On the 

 sardine, however,, there is nothing aside from some extremely simple notes 

 in Dr e Kishinouye's study 15) on the ecology of tne sardine. 



Therefore the autnor, in the early part of November, 1934, and the 

 latter part of June, 1935, at Mitsu Beach in Tagata-gun, Shizuoka 



VII* According to the testimony of Yuzo Masuda, Haruo lamamoto, and other 

 operators: 



19 



