roMPAKATnE STUDY OF sroxinnoTn fishes. 381 



Biology and Ecology. 

 IL\.BIT. 



The scombroid fishes ai'e said to ho ix'lagic, hut only the fishes of the 

 IMfCostei are ti'iily pelagic. The luuckorels, ScomI.er and Ikistrellifjer, live in 

 littoral waters, and most scerfishes too. The tunnies nud Ijonitos, h(wevor, feed, 

 spawn, and giww in the open sea. 



Scoml)roid fishes generally swim to the sliallower stratsi of water at night, 

 and retm-n to the deeper layer in day-time, probablj- following the movement 

 of the plankton, and also that of those aninmLs \\lii(li fce<l on pljiukton. Thus 

 the twilight is the best time for fishing these fishes. 



Scombroid fishes swim near the surface of the sea, in and aftsr tlie spawn- 

 ing sciuson. Tliese fishes are alert and veiy diflicult to catch. They approach 

 the shore in warm seasons, and retire to deeper hiyers of water in ofi"-shore 

 grounds in cold seasons. When a southerly wind blows, the common tunny 

 comes near the surface of the sea, and also approaches the shore. Until recent- 

 ly, no drifters for the timny were found out on the sea, whi;n other winds 

 prevailed. Lightning and the sound of thunder are said to fi-ighten tunnies 

 and bonitos, driving them into deeper strafai of the water. 



Timnies are often said to resort to the neighborhood of deep rocky banks, 

 rising to ca 200 m below the siurface. Especially Parathunnus mebachi S'wim 

 in rather deep layers of water, about one hundred metres below the surface. 

 Tliumms (jeriao is said to descend to a depth of ca 80 m, wliile the other tun- 

 nies can descend to a depth of ca 50 m. In summer, schools of Thunnus ori- 

 entcdis and Neothunnus maa-opterus sometimes swim with the tips of the dorsal 

 fins and the anal out of the water. Bonitos swim quite near the surface of 

 the sea, and seldom descend below forty metres. 



Scombroid fishes often leap out of the water, or show the iX)Sterior por- 

 tion of theh' body, especially when they are feeding. Parathwimis mebachi is 

 Siiid to have a peculiar kibit of leaping out of the water at day-break. 



Scombroid fishes very soon suociunb after a violent convulsion, when caught 

 and taken out of the water. They are very difficult to keep alive, except the 

 common mackerel, as they dart against the fence, when confined in a narrow 

 space, and they can not exist in water of low salinity. Tunnies desert 



