| The phytoplankton and particulate organic matter content are closely related to thewater quality and shrimp health and growth. Shrimp polyculture, as a mode ofecological culture, is very common in the south of China shrimp farming areas.However, the report about the study on the community characteristics of phytoplanktonand total particulate matter in the shrimp polyculture ponds is very limited at present,and the report about the effects of polyculture fish may has on phytoplankton and totalparticulate matter is even less. This article is a study on the community characteristicsof phytoplankton and the composition and content of total particulate matter in theLitopenaeus vannamei, GILI tilapia polyculture water. The results are as follows:1Study on phytoplankton community and suspended particulate matter in GILI tilapiacage polyculture with Litopenaeus vannamei pondsIn order to investigate the culture methods of the new tilapia species, Selectingthree experimental ponds in Dianbai, Maoming city, Guangdong province, the numberwere406,407and408respectively, seting up five cages in each pond, and stockingtilapia in these cages,50,10,150,200and250tails in each cage, respectively.1.1The impact of polycultured Tilapia with Shrimp on phytoplankton community andthe relationship between the composition of phytoplankton dominant species and thegrowth of TilapiaThe effect of tilapia on phytoplankton community and the relevant betweencomposition of phytoplankton dominant species and the growth of tilapia wereconducted in3shrimp–tilapia polyculture ponds. The results showed as follows:(1)During the experiment, Pond406has the dominant species of Microcystis aeruginosa all along, and407,408pond also emerged Microcystis incerta, those results indicatedthat stocking tilapia can’t control the growth and reproduction of cyanobacteria, such asMicrocystis.(2) In the intestinal contents of tilapia detection, we found large number ofM. aeruginosa and much Scenedesmus and Bacillariophyta, not found some othersmall-scale algae which has higher Biomass in the pond Water, such as Microcystisincerta, Chroococcus minutus and Merismopedia tenuis, those results showed thattilapia ingestion has little effect on growth and reproduction of small–scale algae.(3)The tilapia weight gain rate and Special growth rate were407pond>408pond>406pond, and significant difference existed between407pond and406,408pond, thoseresults showed that different composition of dominant phytoplankton species has greatimpact on the growth of tilapia.1.2Total particular matter dynamics and its effects on the growth and survival of Tilapiain the shrimp–tilapia cage polyculture pondsStudy on dynamics of total particular matter (TPM) and particular organic matter(POM) were conducted in3shrimp–tilapia polyculture ponds (406,407and408) duringAugust to October,2010. The effects of POM on the growth and survival of tilapia werealso analyzed. The results showed as follows:(1) The concentration of TPM variedbetween35.0and153.8mg/L with an average of83.1±34.1mg/L; the concentration ofparticular inorganic matter (PIM) varied between19.0and54.0mg/L with an average of34.3±11.8mg/L and took41.28%in TPM; the dry weight of plankton (PZ) variedbetween2.43and22.477mg/L with an average of9.631±5.911mg/L and took11.59%in TPM. Of which, the dry weight of phytoplankton (DWP) ranged from2.298to22.105mg/L with an average of8.987±5.983mg/L and took10.81%in TPM, and thedry weight of zooplankton (DWZ) ranged from0.018to2.724mg/L with an average of0.645±0.607mg/L and took0.78%in TPM; particular debris and bacteria ranged from14.339to97.958mg/L with an average of38.966±25.530mg/L accounted for81.77%ofPOM.（2）The average weight gain rate and specific growth rate of tilapia cultivated inthe cages within Pond407were significantly higher than in the other two ponds.However, there were no significant difference in tilapia survival among the three ponds.2Study on phytoplankton Community and suspended particulate matter in Litopenaeusvannamei–GILI tilapia polycultured enclosuresLitopenaeus vannamei–GILI tilapia enclosure polyculture experiment was conducted in Dianbai, Maoming city, Guangdong province from June to August,2011.Selecting an experiment pond, and seting up24enclosures. These enclosures weredivided into six groups(A, B, C, D, E, F), each group has four parallels, among thesegroups, A, B, C, D and E was experimental group, stocking tilapia4,8,12,18,24tail ineach enclosure, respectively. F was control group, not stocking tilapia. Experimentalgroups and control group all stocking shrimp3000tail each enclosure.2.1The effects of polycultured tilapia in Litopenaeus vannamei’s culture enclosures onthe phytoplankton Community and water quality factorsDuring aquaculture time, investigations of phytoplankton Community and waterquality factors were conducted from June to August,2011. The results showed asfollows:(1) Throughout the culture period, the variation of dissolved oxygen content inmorning was higher than afternoon, culture prophase higher than anaphase, dissolvedoxygen content was close in all group. Nitrite and ammonia concentration showed anincreasing trend in each group, among tham, C and D group were significantly lowerthan A, B, E and F group (P<0.05). The concentration of COD and TOC wereexperimental groups higher than control groups. In the experimental groups, A and Bgroup were higher than C, D and E group. The increase amount of TN and TP, group Ais highest, control group F is lowest, while in experimental groups, A and E were higherthan B, C and D three groups.(2)36phytoplankton species were identified during theculture period. Dominant species is single and prominent. Phytoplankton communitystucture were better in C and D groups than A and B groups. Experimental groupsChlorophylla content were higher than control group, between the experimental groupsA and B were higher than other three groups.2.2The effects of polycultured tilapia in Litopenaeus vannamei’s culture enclosures onsuspended particulate matter and vibrios quantityDuring aquaculture time, investigations of suspended particulate matter and vibriosquantity were conducted in Litopenaeus vannamei–GILI tilapia polyculture enclosures.Moreover, the effects on suspended particulate matter and vibrios quantity in shrimppolyculture enclosures were analyze. The results showed as follows:(1)Throughout theculture period, the dynamic variation of total suspended particulate matter content eachgroups were similar in earlier stage, in the middle and later stage experimental groupswere higher than control groups; POM content of each groups were close and less fluctuation in the whole culture period. PIM content was higher in experimental groupsin the middle and later stage. The percentage of POM and PIM in TPM is close inearlier culture stage, in the later stage the percentage of POM was higher in controlgroups, while the percentage of PIM was higher in experimental groups, among theexperimental groups, the percentage of PIM in C, D and E groups were higher than Aand B groups.(2) The variation of Vibrio quantity was a dynamic process, and higher inthe later culture stage, the number flutuated betweed1.01×10~3to152.33×10~3cell/mL,mean15.08±24.50×10~3cell/mL. In experimental groups, the quantity of Vibrio A groupwas most, followed by group B, group C and D were least. A reasonable density oftilapia polyculture with shrimp conducive to sediment resuspend, promote the organicmatter mineralization and decomposation, control the particulate organic matter contentin aquaculture water, and reduce the number of Vibrio, to create a good ecologicalenvironment for the shrimp growth.3Study on optimal tilapia stocking densities in two polyculture modeWater quality as well as other indexes such as growth, survival, biomassproduction and output value of cultured organisms in pond were evaluated to access aoptimum stocking density of tilapia in polyculture model farming with Litopenaeusvannamei. Our data suggest that:(1) In cage culture pond, there is no significantdifference (P<0.05) in tilapia growth rates between treats with feeding and withoutfeeding, so in a pond rich in nutrition, farming mode without feeding is more reasonablein maintain good water quality, otherwise, proper feeding is required. While only onestocking density was conducted in unfeeding group, the optimal tilapia stocking densityneed further study.(2) In enclosure culture pond, group C had a best output value,highest shrimp survival rates, best water quality, as well as fast growth rates were fondin group C. In summary, treatment stocked with tilapia at0.33ind/m~2and shrimp(about200g) at83ind/m~2are recommended, namely a ratio of250to1for tilapia and shrimprespectively. |
PDF Full Text Request