淡水魚類における個体の比成長と集団の増重量にかんする研究-I

Abstract

The author intended to make clear the variation of the specific growth of an individual fish (R2) in a population and to compare the specific growth of the population ( ?? 1) with the average ( ?? 2) of the R2's obtained. The brown trout measuring eighteen with each fish marked by different tag, were reared in a small pond from July 2 to Augst 28, 1957, and total length of each fish was measured during the course. The results were obtained as follows: 1) although it was recognized that ?? 2 did not coincide with ?? 1 arose from formula (2) and (3) respectively, their difference was very small (Table 1). 2) It was observed that the larger the length of fish, the larger the R2 obtained, and producing a linear relation between them in each of the two periods of growth (Figs. 1 and 2). If the linear relation was expressed as R2=bγ+a (where γ means the representative of the length of a fish in one growth period), then it may be possible to connect ?? 1 with ?? 2 through the formula (5). The ?? 2 in Table 1 also derived from (5) actually produced precise estimate of ?? 2. 3) The fact of positive cor-relation existing between R2 and the length of fish will result the increase of the variation in the length in accordance with the growth of fish. Of population in natural body of water we would expect a more complicated relation existing between R2 and the length of fish than in the present case of confined water. The writer's another experiment of fingerling rainbow trout stocked in a mountain brook well demonstrated the fact, the variation of length of fish being extremely high and increase with the growth of fish.