Journal of the Faculty of Fisheries and Animal Husbandry, Hiroshima University Volume 15 Issue 2
1976-12-25 発行

瀬戸内海におけるウマヅラハギNavodon modestus (GÜNTHER)の漁況について

On the Catch of Navodon modestus (GÜNTHER) in the Seto Inland Sea
Kakuda, Shunpei
In order to clarify various features of the catch of the file-fish, Navodon modestus (GÜNTHER), in the Seto Inland Sea, the commercial catching data of this species were collected and analysed statistically. The data upon which this study is based are compiled from the published records of Ehime Prefecture from 1963 onward and Hiroshima Prefecture during the period 1950-1963 and from the unpublished records obtained from several Fishermen's Cooperative Associations in the Seto Inland Sea. General conclusions obtained in this study are summarized are follows:

1) The file-fish, N. modestus, has always been a common fish of commercial value in the Seto Inland Sea. Generally the catch of this species is more abundant in the western region than the eastern of the Sea in recent years. The main fishing grounds of N. modestus in the Sea are Iyo-nada, Aki-nada (western), Hiuchi-nada (central) and Harima-nada (eastern) (Fig.1). In the western region of the Sea almost all the commercial catch of this species is made with the Kogata-sokobiki-ami (a small beam trawl) and in the central and eastern regions half of the catch with the Masu-ami (a small set net) (Figs.2, 3). N modestus is captured commercially by the Sashi-ami (a gill net), the Maki-ami (a surrounding net), the Ipponzuri (the angling) and the Funabiki-ami (a boat seine), too (Figs.2, 3). While the fishing season of the Kogata-sokobiki-ami lasts from April until December, landing in most abundant in June or July and that of the Masu-ami lasts from April until June, the landing is most abundant in May (Figs. 4, 5).

2) In Hiuchi-nada, central region of the Sea, almost all the commercial catch of N. modestus is hawled in by the Masu-ami during the three months from April to June. This species was very abundant during from 1960 to 1964 in this region, and its annual catch hawled in by about 500 nets of Masu-ami seems to have been 120~150 metric tons (Fig.6). The beginning, the peak and the end in fishing of the Masu-ami are the same in all the fishing grounds in Hiuchi-nada including Kitanada in Harima-nada (Fig.7). The daily catch by the Masu-ami of N modestus shows a considerably sharp fluctuation, a similar fluctuation was observed in each of the other six fishing grounds of Shiraishi-shima, Kitagi-shima, Manabe-shima, Mu-shima, Hashiri-shima and Ohi-shima, eastern part of Hiuchi-nada in 1963 and 1964. But in the four fishing grounds of Yuge-shima, Ohama, Nio and Kitanada, we had only a slight or no significant fluctuation in the same years 1963 and 1964 (Table 1).

3) Two patterns of seasonal variations of the Masu-ami and the Sashi-ami operated near the Masu-ami show nearly the same fluctuation (Fig.8). The abundance of the daily catch of the Masu-ami seems to have a highly significant correlation with the abundance of the Sashi-ami catch operated near the Masu-ami as the result of calculating the correlation coefficient between the two. The sex ratio in N. modestus is likely to be 1: 1, but males are more abundant than females in the samples captured by the Sashi-ami and females are slightly more abundant than males in the samples captured by the Masu-ami during the latter half of the fishing season (Table 2).

4) The annual catch of N. modestus shows irregular and sharp fluctuations in the different fishing grounds (Figs.9, 10). But it is noticed that the annual variation patterns of the catch can be classified into two types in general. One is that the catch was abundant in the first half of the 1960's and about 1970, and the other is that the catch has been abundant from 1969 onward (Fig.12). Moreover, the correlation of variation patterns of the annual catch in the regions of the Seto Inland Sea was examined with the aid of the SPEARMAN'S rank correlation. By the examination it must be concluded that the western region of the Sea including Uwa-kai and the central region of the Sea are independent of each other for the similarity in abundance of the catch. The variation patterns of the western region of the Sea bear a close similarity to those of Sagami Bay (Tables 3, 4).