Abstract
The study has been conducted to know an appropriate feeding strategy and effects of the rearing density on larval growth of the rockfish, Sebastes schlegeli. The results obtained are as fellowed ; 1. Thirty-day-old larvae reached at $25.25{\pm}3.76$ mm in total length and $0.23{\pm}0.07$ g in body weight in experiment A, at which rotifer was provided from the beginning to the end of 30-day experiment, Anemia from 3th to 18th day, and artificial feed from 13th to 30th day after hatching. When rotifer was provided for 30 days, Artemia from 6th to 18th day, and artificial feed from 18th to 30th day after hatching (experiment B), these larvae grew up to $27.52{\pm}2.50$ mm in total length and $0.26{\pm}0.06$ g in body weight. On the other hand, when rotifer and artificial feed were supplied with the same time schedule as shown in experiment B, and Artemia was feed from 6th to 30th day after hatching (experiment C), the total length and body weight of those larvae were $23.22{\pm}3.44$ mm and $0.15{\pm}0.05$ g, respectively. The best result for larval growth was obtained from experiment B. The survival rates estimated were $57.6\%$ in experiment A, $66.4\%$ in experiment B, and $44.4\%$ in experiment C. 2. The growth in total length of the larvae according to their rearing days could be represented by the following equations : Experiment A : Y=4.350+0.116X+$1.887X^2$ (r=0.993) Experiment B : Y=4.500+8.931X+$2.221X^2$ (r=0.994) Experiment C : Y=4.478+5.734X+$1.881X^2$(r=0.990) The average number of Artemia nauplius intaken by the larvae was rapidly increased between 15th and 20th day afer hatching, and 9, 212, 242, 750, and 1,171 nauplius were found in the different sizes of larvae, whose total length were 5.65, 6.81, 9.45, 14.96, and 24.52 mm, respectively. 3. Larval growth in total length and body weight reared at four different densites (A: 1.8 $kg/m^3$, B; 4.0 $kg/m^3$, C; 5.0 $kg/m^3$, D; 6.2 $kg/m^3$) indicated that the best growth was found in experiment A, at which the larval were reared at the lower density and the final survival rates extimated were $92.9\%$ in exp. A, $99.5\%$ in exp. C, $89.0\%$ in exp. B, and $88.2\%$ in exp. D. The amount of production per cubic meter turned out to be 30.45 kg in exp. D, 25.89 kg in exp. C, 20.75 kg in exp. B and 10.48 kg in exp. A. therefore, considering both larval growth and survival rate, higher yields seemed to be attainable at the relatively high-rearing density.
조피볼락, Sebastes schlegeli의 초기성장에 적합한 먹이계열과 사육밀도에 따른 성장을 파악하기 위한 초기의 지수식에 있어서의 먹이계열 시험과 폐쇄순환여과식 사육장치에서 4단계의 밀도(A시험구 : 1.8 $kg/m^3$, B : 4.0 $kg/m^3$, C : 5.0 $kg/m^3$, D : 6.2 $kg/m^3$) 로 조정된 사육시험 결과는 다음과 같다. 1) 3가지 먹이계열 A (rotifer+$3\~18$ Artemia+13 diet), B (rotifer+$6\~18$ Artemia+egg+18 diet), C (rotifer+$6\~30$ Artemia+ 18 diet)로 사육한 자치어의 성장(전장, 체중)은 B ($27.52{\pm}2.50\;mm,\;0.26{\pm}0.06\;g$), A ($25.21{\pm}3.76\;mm,\;0.23{\pm}0.07\;g$), C ($23.22{\pm}3.44\;mm,\;0.15{\pm}0.05\;g$)시험구의 순위였고, 생존율은 B($66.4\%$), A ($57.6\%$), C ($44.4\%$) 시험구의 순위였다. 각 시험구별 자치어의 사육일수에 따른 전장과의 성장관계식은, A 시험구 Y=4.350+0.116X+$1.887X^2$ (r=0.993) B 시험구 Y=4.500+8.931X+$2.221X^2$ (r=0.994) C 시험구 Y=4.478+5.734X+$1.881X^2$ (r=0.990)이었다. 2) 자어의 크기에 따른 개체당 Artemia nauplius의 평균 포식량은 전장5.65 mm일때 9개체, 6.81 mm, 212개체, 9.45 mm, 242개체, 14.96 mm, 750개체, 24.52 mm일때 1,171개체로 전장 $9.45\~24.52$ mm (일령 $15\~20$일) 사이에 급격한 포식량의 증가를 보였다. 3) 폐쇄순환여과 시스템에서 4단계의 밀도별 시험구의 치어성장(평균전장과 체중)은 A ($13.75{\pm}0.76\;cm,\;48.37{\pm}10.61\;g$), B ($13.56{\pm}1.12\;cm,\;44.70{\pm}11.37\;g$), C ($13.22{\pm}1.11\;cm,\;44.03{\pm}10.12\;g$), D ($13.10{\pm}1.12\;cm,\;42.63{\pm}12.91\;g$)시험구의 순으로 저밀도구에서 양호하였고, 최종 생존율은 A $92.9\%,\;C\;91.5%\;B\;89.0\%,D\;88.2\%$ 순위였다. 최종 사육밀도별 단위면적당 총생산량($kg/m^3$)은, D (30.45$kg/m^3$), C (25.89 $kg/m^3$), B(20.75 $kg/m^3$), A (10.48 $kg/m^3$)의 순위로서 개체의 성장과 생존율의 차이는 근소한데 비하여 총생산량에서 큰 차이를 나타내어 동 시험조건에서 경제적인 면을 고려한다aus 고밀도구의 결과가 양호하였다.
(Department of Aquaculture, Cheju National University)