Physiological Responses of Grey Mullet (Mugil cephalus) and Nile Tilapia (Oreochromis niloticus) by Rapid Changes in Salinity of Rearing Water

사육수의 급격한 염분변화에 따른 숭어 (Mugil cephalus)와 틸라피아 (Oreochromis niloticus)의 생리적 반응

Physiological responses (cortisol, glucose, GPT, GOT, total protein, hematocrit, sodium, chloride, potassium, total calcium and osmolality), growth and survival rates of grey mullet (Mugil cephalus) and Nile tilapia (Oreochromis niloticus) by the manipulation of salinity were studied. Salinity was increased directly from freshwater to $33\%_{\circ}$ and remained for 15 days. Then, salinity was decreased directly from seawater to freshwater and remained for other 15 days. All tilapias were dead at the third day, but $96.5\%$ of grey mullet were survived at the 30th day. The grey mullet showed no significant differences for cortisol and glucose concentrations in the seawater and freshwater. However, those of the Nile tilapia were increased in seawater. The grey mullet showed no significant differences for sodium, chloride and potassium concentrations during experimental period. However, those of the Nile tilapia were significantly increased when exposed to seawater. The osmolality of grey mullet ranged between 293.5 mOsm/kg and 335.0 mOsm/kg for the whole experimental period.

염분변화에 따른 생리적 반응과 성장 및 생존율에 관한 기초자료를 얻고자, 해수와 담수에서 광염성 어류로 알려진 숭어와 틸라피아를 재료로 급격한 염분변화 조건에서 어체의 생리적 변화를 조사하였다. 숭어의 코티졸 농도와 글루코스 농도는 해수사육과 담수사육에 유의한 차이를 보이지 않았다. 틸라피아는 해수사육에 따른 증가하는 경향을 나타냈다. 숭어의 $Na^+,\;Cl^-$ 및 $K^+$ 농도는 실험개시시와 차이를 나타내지 않았다. 그러나 틸라피아는 해수사육에 따른 유의한 증가를 보였다. 숭어의 삼투질농도는 293.5$\~$335mOsm/kg 범위를 보였다. 틸라피아는 해수사육 3일째 유의한 증가를 보였다. 생존율에 있어 숭어는 $96.5\%$를 보였고, 틸라피아는 해수사육 3일만에 전량 폐사하였다.