강도다리 Platichthys stellatus 치어의 암모니아 배설에 미치는 수온의 영향

Effect of Water Temperature on Ammonia Excretion of Juvenile Starry Flounder Platichthys stellatus

강도다리 치어(평균 $42.4{\pm}3.4g$, 총 45마리)의 수온(10, 15 그리고 $20^{\circ}C$)에 따른 절식과 식후 총암모니아성 질소 (total ammonia nitrogen, TAN) 배설을 조사하였다. 절식 및 식후 TAN 배설은 순환여과식 시스템 내에서 24시간 동안 3반복으로 측정하였다. 절식 TAN 배설은 실험 수온에 10일 이상 순치한 후 암모니아 측정 시스템에 옮겨 3일간 절식 후 측정하였고, 식후 TAN 배설은 상품 사료(단백질 함량 50.2%)를 하루에 두 번(08 : 00, 16 : 00 h), 7일간 공급한 뒤 실시하였다. 절식과 사료 공급에 따른 TAN 배설은 수온 상승에 따라 증가하였다(p<0.05). 절식 시 수온 10, 15 그리고 $20^{\circ}C$에서 시간당 평균 TAN 배설률은 각각 10.9, 11.2 그리고 $12.2mg\;TAN\;kg\;fish^{-1}\;h^{-1}$이었고, $20^{\circ}C$가 $10^{\circ}C$와 $15^{\circ}C$에 비해 유의적으로 높았다(p<0.05). 식후 시간당 평균 TAN 배설률의 경우 수온 10, 15 그리고 $20^{\circ}C$에서 각각 33.0, 43.4 그리고 $55.3mg\;TAN\;kg\;fish^{-1}\;h^{-1}$으로 나타났다. 두 번의 peak TAN 배설률이 나타났으며, 두 번째 peak가 첫 번째보다 높았다. 최대 TAN 배설률은 최초 사료 공급 10시간 후 나타났으며, 수온 10, 15 그리고 $20^{\circ}C$에서 각각 45.3, 64.5 그리고 $83.2mg\;TAN\;kg\;fish^{-1}\;h^{-1}$이었다. 수온 10, 15 그리고 $20^{\circ}C$에서 섭취한 질소에 대한 TAN 배설 비율은 각각 43.0, 45.7 그리고 48.8%로 나타나 $20^{\circ}C$가 $10^{\circ}C$와 $15^{\circ}C$에 비해 유의적으로 높았다(p<0.05). 이상의 결과는 강도다리 치어의 수온에 따른 암모니아 배설을 추정하고 수질관리 및 사육관리를 위한 실험적 자료를 제공한다.

The effect of water temperature on fasting and post-prandial total ammonia excretion (TAN) of the starry flounder Platichthys stellatus (mean body weigh : $42.4{\pm}3.4g$) was studied. The fasting and post-prandial TAN excretions were measured under three different water temperatures (10, 15 and $20^{\circ}C$) for 24 hours using a recirculating system. In each treatment three replicates were set up and total 45 fish were used. Fish were taken to the indoor aquarium, acclimated over 10 days at three temperatures, and transferred to TAN measuring system for measurements of TAN excretion at the same temperatures. After 3 days of starvation, fasting TAN excretion was measured at each temperature. To investigate post-prandial TAN excretion, fish were hand-fed to satiation level with a commercial diet containing 50.2% crude protein for 7 days, two times daily 08 : 00 and 16 : 00 h. The fasting and postprandial TAN excretion increased with increased water temperature (p<0.05). Mean fasting TAN excretion rates at 10, 15 and $20^{\circ}C$ were 10.9, 11.2 and $12.2mg\;TAN\;kg\;fish^{-1}\;h^{-1}$, respectively. The value at $20^{\circ}C$ was higher than those at 10 and $15^{\circ}C$ (p<0.05), but there was no significant difference between $10^{\circ}C$ and $15^{\circ}C$. Mean post-prandial TAN excretion rates at 10, 15 and $20^{\circ}C$ were 33.0, 43.4 and $55.3mg\;TAN\;kg\;fish^{-1}\;h^{-1}$, respectively. Two peaks of post-prandial TAN excretions were observed, and the second peak was always greater than the first. The post-prandial TAN excretion rate reached to the maximum after 10 hours from the first feeding at $10^{\circ}C$($45.3mg\;TAN\;kg\;fish^{-1}\;h^{-1}$), $15^{\circ}C$ ($64.5mg\;TAN\;kg\;fish^{-1}\;h^{-1}$) and $20^{\circ}C$ ($83.2mg\;TAN\;kg\;fish^{-1}\;h^{-1}$), respectively. The TAN loss for ingested nitrogen at $20^{\circ}C$ (48.8%) was higher than that for $10^{\circ}C$ (43.0%) and $15^{\circ}C$ (45.7%). This study provides empirical data for estimating ammonia excretion and managing culture management of starry flounder under given temperatures.