Reproductive Biology of the Starspotted Dogfish Mustelus manazo from Tokyo Bay, Japan

Abstract

The reproductive biology of the starspotted dogfish Mustelus manazo from Tokyo Bay was examined. The specimens attained their first maturity at 687 mm TL (age 3) for males and 701 mm TL (age 3) for females. All specimens over 780 mm TL (age 5) for males and over 820 mm TL (age 6) for females were fully mature. The gonad index for males reached its minimum during June and July, and maximum ova diameter was the largest in May and June. The fertilized eggs were found in the uteri by early July, and the largest embryos occurred between May and June. It was assumed that the mating, fertilization and parturition occurred during May and June, therefore, the gestation period was estimated at 11-12 months. The litter size increased with total length of the mothers and the fecundity ranged from 2 to 13 embryos. A predominance of males in total number of embryos was observed, but yearly variations were found.