Journal of the Faculty of Fisheries and Animal Husbandry, Hiroshima University Volume 4 Issue 1-2
1962-12-20 発行

Comparison of catches of two pound nets located at different distances from the shore

Kakuda, Shunpei
Onbe, Takashi
The whole daily catches by the two masu-ami (a kind of the pound net) operated in Kasaoka Bay were investigated, with reference to the species and size composition, at about weekly intervals during the one-year period from June, I96I through June, I962, for the purpose of clarifying the difference between the catches. These nets, which were selected as the sample out of the many masu-ami operated in this region, were located off Terama village of Konoshima, one 60 m. and the other 350 m. from the shore. Water depths at the locations of these nets were 3.5 and 5.5 m. below the mean water level respectively. There was no significant difference in such hydrographic conditions as water temperature, chlorinity and dissolved oxygen between the locations of the two nets. From comparison of the catches of the two nets, the following results were obtained:

1) The species composition of the catches of these masu-ami showed considerable seasonal variations and local differences.
2) The catch of the nearshore net was, in general, richer in species, greater in weight and fewer in number of individuals than that of the offshore net. The correlation coefficient between the catches of the two nets either in weight or in number of individuals, was highly significant except in August and September.
3) The number of the captured species was relatively numerous in July and August when water temperature was high. Thereafter, it gradually decreased with the falling water temperature, and remained nearly constant during November and December. The species composition of catches of the two nets, however, always differed from each other.
4) The fishes, larger in size and higher in market value in the catches of masuami, such as Mylio macrocephalus Mugil cephalus and Liza haematocheila except Platycephalus indicus were mainly caught by the nearshore net and seldom came into the offshore net. The number per haul of these fishes was usually small.
5) A large number of young Decapterus maruadsi were caught almost exclusively by the offshore net, practically none of them appeared in the catch of the near shore net. They occurred in Kasaoka Bay in large schools from July through October.
6) There was an indication that small-sized or young fishes are taken more numerously by the offshore net than the nearshore net.
7) The following fishes were presumed to come into Kasaoka Bay in schools. They are Engraulis japonia, Saurida elongata, Allanetta bleekeri, Sphyraena pinguis, Lateolabrax japonicus, Argyrosomus argentatus, Limanda yokohamae and Kareius bicoloratus.