Co-Authors:
Milstein, A., Fish and Aquaculture Research Station, Agriculture Research Organizatiohn, Dor M. P. Hof HaCarmel, Israel
Zoran, M., Fish and Aquaculture Research Station, Agriculture Research Organizatiohn, Dor M. P. Hof HaCarmel, Israel
Kochba, M., Department of Agricultural Engineering Technion, Israel Inst of Technology, Haifa 32000, Israel
Avnimelech, Y., Department of Agricultural Engineering Technion, Israel Inst of Technology, Haifa 32000, Israel
Abstract:
Commercial intensive aquaculture systems were built and are managed in a somewhat different way in each farm. To evaluate the effects of several management procedures on water quality in intensive fish ponds, data from several locations, times and culture conditions in different farms were collected and are herein analyzed through multivariate statistics. Water quality in the intensive ponds depends on the water entering, the biological processes within, and the water leaving the ponds. A reservoir used as source and sink water supplied the intensive ponds with higher organic loading than clear source waters, and its phytoplankton content affected nitrogen cycling within the intensive ponds. The systems with a reservoir had better water quality in the intensive ponds than those with only clean source water. Within the ponds (1) compared to paddle-wheel aeration, aeration by pure oxygen increased oxygen concentration, improved nitrification and promoted decomposition that reduced organic loading. (2) In concrete ponds accumulation of organic matter and development of anerobic conditions on the pond bottom was higher than in the slippery plastic-covered ponds. (3) All intensive ponds provided good growth conditions, tilapia biomass having relatively small influence on water quality. Only in paddle-wheel aerated ponds did increased tilapia biomass increased inorganic nitrogen compounds and soluble phosphorus through excretion, and reduce organic nitrogen through a more efficient removal of food particles. Water leaving the ponds removes matter affecting water quality within the pond. (1) Draining sediments accumulated on the bottom avoided development of anaerobic conditions where denitrification and phosphorus liberation can occur. (2) Water exchange removed particles with nitrifying bacteria and algae that absorb nutrients. A high water exchange rate may have a negative effect from the water quality point of view and from the extra costs incurred in energy and feeds washed out. The processes described occur simultaneously throughout the culture period and shape water quality dynamics in the ponds. This research contributed to the understanding of how management procedures affect the different phases of water quality dynamics in real-scale tilapia commercial intensive systems.
תפריט נגישות
ניגודיות עדינה
מונוכרום
הדגשת קישורים
חסימת אנימציה
פונט קריא
סגור
איפוס הגדרות נגישות
להורדת מודול נגישות חינם
