Ecological Study On The Optimization Of Hyriopsis Cumingii Culture

Hyriopsis cumingii is also called freshwater pearl mussel, which belong toLamellibranchia,Unionoida,Unionidae. H.cumingii is mostly found in shallow lakesand rivers with muddy bottom, and plays an even more important part and contributesover95%of China’s total freshwater pearl production. Traditional pearl culture needsfrequent fertilization with organic materials to cultivate phytoplankton for the crops,consequently resulting in high loads of nutrients and the frequent outbreak ofcyanobacteria bloom in the mussel ponds, and this has become one of the majortechnologies of pearl farming in China. Because of the cyanobacteria blooming, will notonly made the poor palatability of algae, but also become an obstacle to the sustainabledevelopment of this industry. We should solve the problem, and first of all we shouldstudy cultivation mode of Hyriopsis cumingii. We should study cultivation mode ofHyriopsis cumingii，and can be cast from improving the composition of organicfertilizer and breeding ecology.This paper studied on effects of three phylum of microalgae on absorption, OxygenConsumption and Ammonia-N Excretion Rates of Freshwater mussel, the basalmetabolism of Hyriopsis cumingii to discuss filter-feeding, digestion, metabolism andother important physiological indicators, and the effect of different collection mode toimprove the freshwater pearl culture through changing the structure of phytoplankton,water quality and production, then we find the provide basic data for the specialfertilizer and optimal coculturing ratio （prawn or fish） and density to supply a solid baseof theory for optimization of culturing the freshwater pearl mussel. The result is below:1. Basal metabolism of Hyriopsis cumingii in the different of densityBasal metabolism in the different of density was determined during the24hourstrial, under water temperature21℃. Results showed: the excretion of Hyriopsiscumingii of ammonia nitrogen, TP and density were positively correlated relationship in14.43±0.21g/L-54.45±3.22g/L. But ammonia nitrogen, TP began to fall in70.29±2.33g/L, and began to appear a certain amount of stress response. The oxygen consumption rate with the increase of density rise ceaselessly, present positive correlation. Rising asthe density （14.43±0.21g/L-41.65±0.82g/L;54.45±3.22g/L-82.13±2.55g/L）,O/N risegradually, present positive correlation. The O:N ratio revealed that freshwater musselconsumed protein when the density is14.43±0.21g/L or54.45±3.22g/L. Based on thisdensity, O/N rise gradually with the rising density, the freshwater mussel consumedmore fat and protein. The life activities in low density and the optimum density.2. Effects of three phylum of microalgae on absorption, Oxygen Consumption andAmmonia-N Excretion Rates of Freshwater musselAbsorption efficiency （AE） of fed on three phylum of microalgae was determinedduring the24hours trial, under water temperature21℃. Oxygen consumption andammonia-N excretion rates of freshwater mussel regulars were also studied inlaboratory. Results showed that AE of freshwater mussel on Bacillariophyta was betterthan other two phylum of microalgae at the same concentration, were0.660±0.003,0.142±0.003and0.095±0.004, respectively. In the Cyanophyta group, the highestoxygen rates of consumption and the highest ammonia-N excretion rates were foundwhich were1.346±0.024μg/（g h） and25.78±0.237μg/（g h）, respectively. The lowestammonia-N excretion rates were0.795±0.015μg/（g h） in Chlorophyta group, while thelowest oxygen rates of consumption were13.307±0.127μg/（g h） in the Bacillariophytagroup. Furthermore, the O:N ratio revealed that freshwater mussel consumed proteinwhen they fed on Bacillariophyta, but may consumed more fat and protein when theyfed on Cyanophyta or Chlorophyta.3. The cultivation experiments of coculturing mussel of semi-enclosed prawnponds（1） The impact on water quality and production of coculturing mussel of semi-enclosedprawn pondsThe present study was conducted simultaneously in six semi-enclosedprawn-farming ponds located in Haiyan County （Zhejiang Province, China）. Pond areasvary from2000to2467m². The comparable ponds have similar pond area:1#and2#ponds are2000m²,3#and4#ponds are2333m², and5#and6#ponds are2467m². Allponds are connected with a nearby river via a long narrow canal which is closed by asluice-gate. During the study period （June-August,2011）, the water depth in the pondswas maintained at2m by adding freshwater via the sluice-gate approximately everymonths. Including NO₃, NO₂, NH₃-N, COD, TN, TP, PH, transparency, and so on. Production of shrimp is in August. Results showed that the water quality of polycultureis better than monoculture. The NO₂、NH₃-N、TN、TP and DP is become more better.Results also revealed that prawn production significantly increased in the polyculturesystem compared with the prawn monoculture system. because of the predation,Hyriopsis cumingii massive dead. The survival rate of Hyriopsis cumingii is below25%.So coculturing mussel of semi-enclosed prawn is benefit to prawn, and harmful toHyriopsis cumingii.（2） The impact on phytoplankton of Hyriopsis cumingii and prawnThe experiment compared the quantity, biomass and dominant species ofphytoplankton in different enclosures monoculture of Hyriopsis cumingii and prawn.Phytoplankton density in polyculture decreased from10412.34x104ind/L to5404.63x104ind/L; but in monoculture, phytoplankton density rose from9467.44x104ind/L to11787.12x104ind/L. And the biomass of phytoplankton in polyculture rosefrom10.03mg/L to17.51mg/L; but decreased from19.27mg/L to9.77mg/L. Whichindicated that polyculture can control the number of algae, improve the biomass ofphytoplankton, make the algae presents large-scale trend. Dominant species of thecontrol comprised of Cyanophyta （Microcystis flos-aquae, Merismopedia punctata andMerismopedia tenuissima）, Chlorophyta （Crucigenia apiculata） and Bacillariophyta（Synedra acus and Cyclotella meneghiniana）. For the test treatment, the situation wasreversed where Cyanophyta （Oscillatoria splendid and Phormidium tenue）, Chlorophyta（Crucigenia quadrata, Scenedesmus armatus var. boglariensis and Scenedesmusdimorphus）, Euglenophyta （Trachelomonas margaritifera, Euglena geniculata andStrombomonas ensifera） predominated. Cyanophyta was the most abundant group in thecontrol （54.9%for total abundance in percent）, while Euglenophyta was the mostabundant group in the test treatment （21.28%for total abundance in percent）.4. The cultivation experiments of coculturing mussel of fishpond（1） The impact on water quality and production of coculturing mussel of fishpondThe present study was conducted simultaneously in six fishponds located DuchangCounty （Jiangxi Province, China）. Pond areas are6667m²,and the depth of water is1.63m in average. The density of fish is1.5ind/m³,and the density of Hyriopsiscumingii respectively are0.8ind/m³，1.0ind/m³and1.2ind/m³. During the studyperiod （April-December,2012）, the water depth in the ponds was maintained at2m byadding freshwater via the sluice-gate approximately every months. Including NO₃, NO₂, NH₃-N, COD, TN, TP, PH, transparency, and so on. Production of shrimp is in April andDecember. Results showed that that the water quality of the density of1.0ind/m³is thebest ones. NO₃, NO₂, NH₃-N, COD, TN, TP, PH, transparency all significantly lowerthan0.8ind/m³and1.2ind/m³, and more significantly lower than monoculture. Fromthe survival rate of mussel, C pond （1.2ind/m³）, clam pond minimum average survivalrate is75.23%, A pond （only0.8ind/m³） survival rate up to89.06%. From theperspective of the production of fish, fish survival rate and the average growth rate inwet weight collection ponds were superior to single monoculture. Breeding density forthe survival rate of fishes in the pond is only0.8ind/m³and wet weight average highestgrowth rates.（2） The impact on phytoplankton of Hyriopsis cumingii and fishThe experiment compared the quantity, biomass and dominant species ofphytoplankton in different enclosures monoculture of Hyriopsis cumingii and fish.Results showed that the number of algae the most obvious decline in the density of fishis1.2ind/m³. Phytoplankton biomass all increased in the three collection ponds. Whichindicated that polyculture can control the number of algae, improve the biomass ofphytoplankton, make the algae presents large-scale trend.91,90,90and76phytoplankton species were identified within A,B,C and monoculture.