COMPARATIVE STUDY OF SCOMBROID FISHES. 
391 
with our species or not. The Hawaiian species looks quite similar to our species 
in external characters ; hut minute examination is necessary for identification. 
So far as I know the plecostean Ashes are most rich in number of species 
in our waters. Among our tunnies, Thunnus orientalis is rather widely distribut¬ 
ed. Neothunnus rarus is found only in Kyushyu and the south-western part of 
the Japan Sea. In the Japan Sea we find only three species of tunny ;— 
Thunnus orientalis, Neothunnus macropterus, and Neothunnus rarus. The latter 
two species, however, are very few in number, and there is no regular fishing 
for them. All the species of tunuies found in the Japan Sea live near 
the surface and approach the coast. The tunnies inhabiting off-shore grounds 
and descending into rather deep strata of water have not yet been found in the 
Japan Sea. This is most probably due to the fact that the temperature of 
the sea is too cold for these species. Bonitos are also found in the Japan 
Sea ; but rather few in number, and Euthynnus yaito is very rare. 
The scombroid fishes with the air-bladder have generally a wider range 
of vertical distribution than those without it. The latter group of fish is 
often restricted to the surface of the water. Or they are near the surface 
in some seasons, and descend to deeper layers of the sea in other seasons. 
They can not change their abode suddenly, but when the change is gradual 
they can endure it. Most scombroid fishes swim in shallow strata of 
water, but tunnies generally, especially Farathunnus mehachi, are found in 
deeper strata of Avater than bonitos. Bonitos and voracious species of the 
Cybiidae frequent the surface of the sea and are readily attracted to artificial 
baits. These fishes are rarely found in deeper strata than about 80 m. 
The scombroid fishes are found in warm seas, the majority of them be¬ 
longing to the tropical and subtropical regions, and most of them are very widely 
distributed. They swim very fast in search of prey, and many of them have 
their own blood-temperature as higher animals. Our common mackerel and the 
striped bonito are cosmopolitan species. The long-finned tunny ( Thunmis germo ) 
and Acanthocybium solandri, too, seem to be Avidely distributed, though a 
critical determination of the species from different parts of the world has not 
yet been made. The following tables illustrate the distribution of scombroid 
fishes in our waters and adjacent regions. 
