| The budgets of carbon, nitrogen, phosphorus and energy in 6 shrimp engineering culture systems (SECS) were deal with in this paper. The shirimp Litopenaeus vannamei with initial body weight of 0.098±0.013g was stocking at 700 ind./m3 and 1250 ind./m3 both with three repeats. The experiment was finished in 94d and only pellet feed was used. Only 1.10% of the total water was replaced by fresh seawater every other day during experiment period. The means of survival rates and ultimate body weight is 81.12±4.94% and 2.33±0.08g, respectively. The production of shrimp is 1.75±0.17kg/ m3. The FCR(%) is 14.70±0.73. Main results according to 6 SECS as follows: 1. The water quality factors (WQF) fluctuation 1.1 Some WQF have increased during experiment period. Such as: Dissolved organic carbon and nitrogen (DOC and DON) has increased by 113.24% and 43.80%. Particulate organic carbon and nitrogen (POC and PON) have increased by 133.70% and 91.67%. There was 75.75% increase on chemical oxygen demand (COD). At last, the ultimate concentration of nitrate is 21.984±1.523mgN/L and is far above the initial nitrate concentration. These increasing water quality factors are all negative (NWQF) to shrimp culture. However, the all NWQF were safety to shrimp in SECS. In common, the descending order of NWQF is as follows: shrimp culture tank > deposition tank > microbe tank. It proved that water treatment part work well. 1.2 A few of WQF have decreased with SECS running. These decreasing WQF are all positive (PWQF) to shrimp culture. Such as dissolved oxygen concentration (DO) in shrimp culture tank had a slight downward trend with SECS running. It's reason that the respiration of shrimp increased with growing. However, the means of DO in SECS is 6.59±0.11mgO2/L above 5 mgO2/L. It showed that SECS had good aerator system. 1.3 Other WQF are litmusless (LWQF) to shrimp culture. LWQF should be stable or fluctuate between a fitting range. Otherwise, LWQF would be adverse to shrimp culture. LWQF include salinity, pH and temperature and so on. In these SECS, salinity was 31.5 and stable because of little water exchange. Temperature varied among 21℃～29℃ with season. The means of pH was 7.88±0.01 and stable because the corallite in deposition tank can adjust pH. All that also showed the water treatment part running well. 1.4 It's reported that safe nitrate concentration to shrimp is below 150mgN/L. In this one crop of shrimp culture, water nitrate concentration went up and can reach the maximal 30.74mgN/L at last. It shows that three crops of shrimp culture one year be feasible before the whole water in SECS be changed. However, successive shrimp culture couldn't exceed five crops. 2. The budgets of carbon 2.1 The equation of carbon budgets as follows: Feed (100%) = Shrimp assimilated (30.60%) + System filtered (36.77%) + System transformed (10.91%) + Accumulated in water (1.02) + Pipe consumed (20.70%). 2.2 The average ratio of carbon shrimp eaten to total feed carbon used (narrow sense food taken rates, nFTR) is 54.39%. And the carbon assimilated by shrimp is 30.60% of total feed carbon used (TFC). The carbon accumulated in harvested shrimp (the ratio of growth carbon, RGC) is 13.60% of TFC. The RGC is observably bigger than that of in shrimp culture in nature tank and the Lindeman's efficiency. In another word, the carbon utilized efficiency in SECS was improved. 2.3 In SECS, carbon filtered (including excess food, feces, molted shells and waste water) is 37.00% of TFC, so the function of filtering part is very important. 2.4 Carbon transformed in system (including respiration of corallite, microbe ball and water)is 10.91% of TFC. When experiment finished, the concentrations of dissolved organic carbon (DOC) and particulate organic carbon (POC) was only 8.80mgC/L and 2.38mgC/L. So water treatment parts run well and the quality of system water was limpidity. In a word, basing on the budgets of carbon, SECS is feasible and promising. 3. The budgets of nitrogen 3.1 The equation of nitrogen budgets as follows: Feed (100%)... |
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