볼락, Sebastes inermis cuvier의 초기성장과 생식소 발달과정에 관한 연구

Abstract

The objective of this study was to examine the early growth of rockfish Sebastes inermis Cuvier from a series of reared specimens for provide information to fisheries biology and more information on the aspect of aquaculture in the larvae of this species. Rockfish were reared in farm and sampled preiodically for developmental study until 1,350 days after parturition.

An increase in total length of fish indicated continuous growth, described by the growth expression of the type TL=0.0217X (r2=0.8867, where TL is total length and X is at days after parturition) and BW=0.0001X2+0.0713X (r2=0.9858, where BW is body weight and X is at days after parturition), respectively. The expression for the relationship of body weight and total length is BW=0.0072TL3.4373 (r2=0.9945, where BW is body weight and TL is total length). The expression for the relationship of eye diameter and days after parturition is ED=-0.0000X2+0.0326X (r2=0.9886, where ED is eye diameter and X is days after parturition). Relationship of head length (HL), snout length (SL), eye diameter (ED) and postorbital head length (PHL) with total length (TL) expressed the type of HL=0.2652TL (r2=0.9758), SL=0.0613TL (r2=0.9602), ED=0.0752TL (r2=0.9715) and PHL=0.2652TL (r2=0.9501), respectively.

The early gonadal development and sexual differentiation of rockfish was described from parturition stage to 400th day after-parturition. During this period, the average total length (TL) of their body grew from 0.57 cm to 13.18 cm. The primordial germ cells (PGCs) was remarkably observed at 0,68 cm TL larva (10th day after-parturition). At 1.52 cm TL (50th day after-parturition), initial ovarian differentiation was identified by PGCs containing condensed chromatin, and their transformation into meiotic oocytes. Finally, at 10.23 cm TL (300th day after-parturition), the ovaries gradually developed to the oocytes in the primary yolk stages. While ovaries grew rapidly after sex was differentiated, testis contiued to multiply, but not undergo growth until at 6.97 cm TL (200th day after-parturition). Testis contained, at 6.97 cm TL (200th day after-parturition), the spermatocytes occurring the meiotic activity, spermatogonia, and cyst cell. The result shows that sex differentiation type of rockfish belongs to the differentiated gonochorism. The sex ratio of rockfish at 400th and 800th day after-parturition both showed higher percentage of male apperance (P<0.05).