Spawning Period and Size at Maturity of the Ocellate Spot Skate Okamejei kenojei in the West Sea of Korea

Abstract

This study aimed to investigate the gonadal development process and size at maturity of the ocellate spot skate Okamejei kenojei (Müller and Henle, 1841). In total, 1234 specimens were collected from the center of the Korean West Sea between January 2019 and December 2020. The maturity stage of the gonads of each individual was determined visually based on size, color, and egg size. To estimate the spawning period, each specimen was measured for disc width, body weight, and gonad weight, and the monthly gonadosomatic index (GSI) was derived. The GSI of the specimens peaked in April and May, and the main spawning period occurred during June and July. Egg capsules were first observed in specimens collected in March and were most commonly observed in specimens collected in July (56.8%). The maturity ogives for disc widths of female specimens at 50%, 75%, and 97.5% maturity were 26.6, 27.9, and 30.8 cm, respectively, whereas those of male specimens were 26.2, 27.5, and 30.7 cm. The findings of this study provide basic information on reproductive ecology related to the fertility of the ocellate spot skate.