播磨灘,大阪湾におけるイカナゴ発生量変動に関する研究-IV : 産卵量との関係

概要

論文の詳細を見る
The present paper deals with the relation between the number of eggs spawned and the fluctuation of the abundance of larval sand-lance in Harima-nada and Osaka Bay, using the data obtained between 1956 and 1966. The following results were obtained, 1) The total length of adult fish measured during the spawning season was as follows, 1-age fish 81.6±8.1mm. 2-and 3-age fish 118.9±5.8mm. In years when catch of adult was large the body length of 1-age fish was small. 2) The sex ratio of adult fish was considered to be 1:1. The catch in weight was transformed into number of individuals by using the age-com-position and the mean body weight of each age-group; and then the relative number of eggs spawned was estimated using the sex ratio and fecundity of females in each age-group, based on the assumption that the fishing rate is constant every year. 3) The number of eggs spawned by 2-and 3-age fish occupies 63-95% (Av. 76%) of total number of eggs spawned. 4) A negative correlation between the above mentioned number of eggs spawned and 0-age individuals in catch was obtained, viz. r=-0.811. This is expressed by the formula, Y=2.459-0.608X. (Where Y is log. of 0-age individuals in catch, and X is number of eggs spawned.)