エゾアワビの生態学的研究-IV : 成長に関する研究

概要

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Since it was clarified by the author that the age of the abalone, Haliotis discus hannai, can be determined by means of counting annual rings of the shell, the present study has been made to search the growth of abalones in nature in the region of Onagawa Bay, Miyagi Prefecture. While by rearing experiments the seasonal changes of growth and fatness, and the effect of the environmental factors such as water temperature and food on the growth have been investigated. 1. In rearing experiments, it is assumed that the growth of abalone is slowed down in winter, and in water temperature below 7°C almost no growth takes place. As the water temperature rises, they show rapid growth, reaching maximum in the period from April to June. In the period from August to October their growth is again slowed down and their weight decreases temporally. The decrease of growth rate in autumn is assumed not to be due to the decrease of water temperature, but to the maturation of gonad. The abalone gains flesh remarkably from February to July. Thereafter it gets thin in consequence of the spawning. In winter it begins to gain flesh again. 2. The growth rate of the natural abalone in the principal fishery areas of Onagawa Bay is shown in Table 3. Their growth differs somewhat from place to place, but in general, their shell length becomes 4.7cm in 2 years, 8.5cm in 4 years, and 10cm in 5 years.