COMPARATIVE STUDY OF SCOMBROID FISHES. 
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vertebral column, it can not be easily bent. The tail-fin is rigid and lunate, 
its quick and powerful strokes can be understood from the quick and high 
pitched sound produced by the fish in its death-struggle on the deck of a boat 
when caught. If a landing hook is driven by mistake into the caudal peduncle of 
a tunny, we can not hold it, as the hands become paralyzed from the violent 
convulsion of the muscles. Neither can we hold, even for a few seconds, a 
landing hook driven accidentally into a tunny swimming away from our boat. 
Really bonitos and tunnies swim like meteors. The troll-line for tunnies as 
well as the line attached to a harpoon-head used in tunny-fishing require a 
reserve of at least 200 m, though the troll-line for a seerfish lias a reserve of 
only 30 m or often none at all. 
MIGRATION. 
The scombroid fishes, especially the plecosteans are good swimmers, and as 
they are voracious, they are forced to swim about incessantly in search of 
food. Like many other fishes, scombroid fishes generally swim in shallower 
strata of water at night, and seek the deeper strata in day-time. They migrate 
more or less according to the change of temperature. In the cold season 
they seek lower latitudes, in summer they go further north ; but Gybium 
comrnerson seems to be exceptional, visiting the western coast of Hondo in 
the Japan Sea in winter only. The migration of the striped boni to is also 
remarkable. On the Pacific coast the fish migrate with the warm current and 
in summer they reach the southeastern coast of Hokkaido and remain there 
till autumn. In then northerly migration they approach the coast, but in 
moving south they swim off-shore. In the Japan Sea they take a quite 
different course, approaching the coast in their southerly migration in the cold 
season. The migration of Thunnus orientalis and Th. germo in the Pacific 
coast is nearly the same as that of the striped bonito. Thunnus orientalis in 
the Japan Sea approaches the coast in going north, in early summer. 
Generally speaking of scombroid fishes, large and old are caught at the 
beginning of the fishing season, while at the end of the season only young 
and small ones are found. 
