Analysis of Physical and Chemical Factors of Sea Water in Commercial Breeding of Epinephelus coioides

Key words: 
• Epinephelus coioides /
• breeding way /
• physical and chemical elements

Abstract: Sea water in the breeding ponds for commercial breeding of Epinephelus coioides based on detrital food chain was analyzed to observe the changes of and relation among its physical and chemical elements such as ammonia nitrogen,Nitrate （ NO₃^--N） ,nitrite （ NO₂^--N） ,dissolved oxygen,pH,etc. to improve its breeding method. With the breeding time going on,nitrate （ NO₃^--N） and nitrite nitrogen （NO₂^--N） content tended to increase and showed a significant linear relationship:y=4. 3854x0.287,R² =0.8625; the dissolved oxygen content of the sea water was over 5. 7 mg·L^-1 ; pH ranged from 7. 15 to 7. 92; the ammonia nitrogen content was above 5 mg·L^-1 in the late stage of breeding; temperature ranged from 27 ℃ to 29 ℃ ; salinity changed from 30 to 34; average light intensity ranged from 1 075 lx to 2 329 lx; direct sunlight water area and hours during the day also showed a linear relationship,y = 0. 017 7x2-0. 187 8x + 0. 524 3,R²=0.9799. The levels of ammonia nitrogen,nitrate （ NO₃^--N） ,nitrite nitrogen （NO₂^--N） ,dissolved oxygen and pH in the pond bottom were significantly different from those in the surface and intermediate layers of sea water. All the fries lived normally during breeding.