抄録
In the two previous papers, the floating seaweeds in the sea to the west of Kyushu in May of 1964 were described. In this third report, a rough estimate of the population size of the “mojako” in the same sea and period is dealt with, on the assumption that the “mojako” inhabits only under the floating seaweeds.
The results obtained are as follows:
1) The value of MORISITA's Iδ-index as an index of dispersion is significantly greater than 1, and the “mojako” shoal is a negative binomial in type of frequency distribution of CPUE, as shown in Fig. 1 and Fig. 2. From these facts aforementioned, it seems that the fish shoal has a tendency to follow a concentrating pattern of distribution. Such a pattern of distribution may be due to the fact that the fish are enticed by the floating seaweeds.
2) Judging from the pattern of distribution aforementioned, it seems to be only natural that the catch of the “mojako” should greatly fluctuate.
3) The population size of the “mojako” in the sea to the west of Kyushu in May of 1964 has been estimated at one hundred and fifty thousand in number as shown in Table 1. The figure is based on the relationship between the density of the fish (living under the floating seaweeds) obtained by the vessels, and the amount of the floating seaweeds observed from the air.
