ウマヅラハギNavodon modestusの肥満度についての大繁殖期と小繁殖期との比較

ウマヅラハギの肥満度を小繁殖期の1964年に採集した標本と大繁殖期に該当する1976年と1980年に採集した標本について雌雄別に求め,体長範囲がほぼ等しい標本間で相互に比較し,検討した。大繁殖期の肥満度は1.46－2.39であって,小繁殖期の肥満度1.94－2.89と比較してかなり小さく,その平均値の差は統計的に有意である。このような肥満度の差は大繁殖期と小繁殖期とにおける生息密度の差に起因する個体当りの餌生物量の多少によるものと推察される。

なお,大繁殖期と小繁殖期の両期ともに,同一標本の雌雄間においては肥満度の平均値に差は認められない。

The present paper aims to represent an example of the density effect in fish populations.

In order to compare the coefficient of fatness, which is induced from the cubic representation, of fish between two different populations, i.e., an exuberant population and a relatively sparse population, the file-fish (Navodon modestus) was sampled in the Seto Inland Sea and the adjacent sea waters (Fig. 1). The file-fish from the exuberant population was sampled in 1976 and 1980, and those of the sparse population in 1964 as shown in Table 1. The range of standard length of each sample from both populations was nearly equal except for Sample II in Table 1 (Fig. 3-5).

The coefficient of fatness of the file-fish from a relatively sparse population ranged from 1.94 to 2.89. On the other hand, that of an exuberant population except Sample II fell into the region of 1.46－2.39 (Table 2, Fig. 6). Accordingly, significant differences existed statistically between the mean values of the coefficients of the two different populations. And there existed no significant difference in the mean coefficient between female and male in the same population (Table 4). It is presumed that these differences in the coefficient of fatness of the file-fish between an exuberant and a relatively sparse populations may be caused by the difference of the volume of food organisms per individual.