小田和湾の藻場におけるウミタナゴ類3種の生長および再生産

Abstract

1) The seasonal growth pattern and the reproductive processes of embiotocid fishes around Odawa Bay, Kanagawa Prefecture, are examined on the basis of measuring age, body length and weight, fat weight, gonad weight, and the size and number of young in brood. 2) Two regression straight lines fit the data of relations between body length and body weight for females and two or three regression lines may be applied to the data of relations between total body length and body weight for embryos at the stage of gestation in the ovary of female mother of three species of embiotocid fishes. 3) The value of the coefficient of variation is shown to continue to rise up until the individuals reach about 70mm in fork length, then gradually decreased as the individuals grew older. 4) The growing season is seen to occur roughly from May to September and the non-growing season from October to February of the next year. In D. viridis and D. temmincki, the males are 2 or 3mm bigger in mean body length than the females during the growing season of the first year but during the growing season of second year, the females are bigger than the males. 5) A time lag of about six months between males and females of D. viridis and D. temmincki is seen in the reproductive cycle and the fat contained have a close relation to sexual maturation. 6) Embryos are born at the stage of juvenile or young after about 3 months gestation in the ovaries of females. In 1+year old mother, D. viridis has generally 12-13 young, N. ransonneti has 10-11 young and D. temmincki has 8-9 young. The size of young born is the biggest in D. temmincki and the smallest in N. ransonneti.