대형 수조에서 볼락 종묘 생산에 따른 수질 환경의 변화

Abstract

An experiment was carried out to investigate changing of water quality during the seed production of dark-banded rockfish Sebastes inermis in large scale tanks. Ten broodstock of dark-banded rockfish were held in three circular tanks (diameter 6.5 m; depth 2 m; water volume 50 ton) each (stocking density 0.061kg/m3 ). During the experiment the temperature ranged from 14.2 to 16.1∘C . The fingerlings were 134 with rotifers only during 1 to 9 days after parturition, rotifers with Artemia nauplii during 10 to 20 days after parturition, Artemia nauplii only during 21 to 35 days after parturition, Artemia nauplii with commercial diet during 36 to 80 days after parturition and commercial diet only during 81 to 85 days after parturition. Water quality (dissolved oxygen, pH, NH+4−N,NO−2−N,NO−3−NandPO3−4−P ) in rearing tanks measured every 5 days in long term monitoring investigation or every 2 hours in diurnal monitoring investigation. In 85 days after parturition, the body weight of fish grew up to 0.88 f and specific growth rate was 8.0%/day in body weight. In long term monitoring investigation, with the increase of the amount of supplied commercial diet, the concentration of dissolved oxygen (DO) and pH decreased, but the concentration of NH+4−N(4.5to76.3μM),NO−2−N(0.02to0.06μM),NO−3−N(3.0to5.9μM) , and PO3−4−P(0.41to0.59μM) increased. In the diurnal monitoring investigation, the concentration of NH+4−N showed great fluctuation and ranged from 3.0 to 9.1μM when fed rotifers, 16.3 to 45.8μM when fed Artemia nauplii and 36.5 to 120.1μM when fed commercial diet. After daily feeding with each of feed, the amount of dissolved inorganic nitrogen (DIN) and phosphorus (P) wastage were 7.0 g and 0.7 g when fed rotifers, 24.7 g and 0.7 g when fed Artemia nauplii and 140.9 g and 2.2 g when 134 commercial diet. The amount of DIN and phosphorous wastage during 134 commercial diet was significantly higher than that of fed rotifer and Artemia nauplii (P<0.05). Results will provide valuable information for water quality management and culture of dark-banded rockfish in commercial seed production systems.