Growth And Development Of Vietnamese Pond And River Culture Hyriopsis Cumingii And Analysis Of Important Water Environmental Factors

This paper reports the results of the study on growth of cultured Hyriopsis cumingii in Vietnam and several other factors(water quality factors,phytoplankton in water,and gonad development).The research content includes4 parts:(1)The growth of Hyriopsis cumingii in pond culture(Experiment I),(2)the growth of Hyriopsis cumingii in river culture(Experiment II),(3)Evaluation of gonadal development in the experiment,(4)Analysis of phytoplankton and several factors of water quality in the hanging experiment.The research was done in Hua Dong Township,Thuy Nguyen district,Hai phong City,Vietnam.The research period was from 15/6/2017 to 30/7/2018.The experimental results are as follows:In the experimental period,fast growth for shell length,shell width,and shell height were recorded between 60 to 180 days old(later autumn and early winter);the time range from 180 to 270 days old(later winter and early spring)registered the slow growth;the slowest period was from 210 to 240 days old(water temperature was the lowest);270 to 330 days old(later summer and early autumn)because water temperature gradually increased so the growth speed also increased gradually;300 to 360 days old was the fastest growth speed period;360 to 420 days old speed of growth became slower.The shell character and body weight of Experiment I(pond)were higher than Experiment II(river).Hyriopsis cumingii in the pond(Ex I),average daily growth rate(ADG_L)of90 days old reached the highest speed of growth,shell length was 0.548mm/d,shell height was 0.127mm/d and shell width was 0.111mm/d.ADG_L of 120 days old shell length,shell height and shell width were 0.388mm/d,0.116mm/d and0.110mm/d;150 days old were 0.416mm/d,0.103mm/d and 0.218mm/d.In the river(Ex II)ADG_L of 90 old days were 0.479mm/d,0.134mm/d and0.147mm/d.Result of ADG_L indicated that the growth trend in shell length,shell height and shell width were the fastest from 90 to 150 days old,and the slowest from 180 to 240 days old.Hyriopsis cumingii in Ex I,specific growth rate(SGR)of 60-90 days old shell length reached the highest speed of growth(1.389±0.06%/d),there was statistically significant difference(P<0.05)as compared to another period.90-150 days old SGR speed of growth was slow(0.722–0.631%/d),150-240 days old period grow speed was low 0.054–0.086%/d.In Ex II shell length,shell height and shell width were 1.388%/d,2.163%/d and 0.147%/d;180-210 old days were 0.328%/d,0.497%/d,0.503%/d.Hyriopsis cumingii in Ex I,the highest average body weight(Wb)reached48.57±9.13 g and in Ex II reached 44.98±8.73g,obvious difference.In the full experimental period Wb of Ex I and II had no obvious significant difference.60-180 days old is the fastest speed growth of Wb period;120-210 days old is slow speed growth of Wb;270-300 days old is fast speed growth of Wb.180-240 days old body weight average daily growth rate(ADGw)of Hyriopsis cumingii in Ex I lower than in Ex II,this period ADGw of Hyriopsis cumingii in Ex II seems not to have changed.ADGw of Hyriopsis cumingii in Ex I 180-210 days old increased progressively,in 210 days old Ex I and II had no significant difference(P>0.05).The fastest speed of ADGw was at 150 days old(Ex I was 0.473±0,011(g/d)and Ex II was 0.381±0.065(g/d).150-180 days old ADGw speed was slow down,in Ex I was 0.059±0.022(g/d)and Ex II was 0.085±0.031(g/d).210-240days old ADGw speed slower,Ex I was 0.028±0.022(g/d),Ex II was0.077±0.032(g/d).Specifc growth rate of body weight(SGR_w)at 60-90 days old was the hightest speed,Ex I and II were 3.882%/d and 4,668%/d.180-210 days old was the slowest speed period,Ex I and II were 0,079%/d and 0.998%/d.In the full of period,average of SGR_w in Ex I and II was 1.410%/d and 1.574%/d,the difference had no statistically significant(P>0.05),120-270 SGR_wthe difference was not significant(P>0.05).The microalgae in the water was much,included approximately 71 species,8 phylum.Ex I Chlorophyta dominates;Ex II Bacillariophyta dominates,Ex I feature was Pediastrum sp.Chlorophyll of Ex I was higher than Ex II.Chlorophyll of Ex I was 78.3%,Cyanophyta was 69.2%,Chlorophyll of Ex II was 52.2%,Cyanophyta was 61.5%,in the Ex II the main algea was Bacillariophyta.The amount of phytoplankton in the Ex I was higher than in the Ex II,but the diversity index was lower than the Ex II.Water environmental indicators studied included water temperature,p H,transparency(SD),dissolved oxygen(DO),water salinity(S),and water hardness(H).The average water temperature range of Ex I and II in the water temperature study period was 25.5~oC-36.5~oC and 24~oC-32.5~oC respectively.The water temperature of the Ex I maximum was 36.5~oC and the minimum was 25.5~oC,The Ex II maximum was 32.5~oC and minimum was 24~oC,two experiments provided suitable habitat and temperature range for Hyriopsis cumingii.The average transparency Ex I was higher than the Ex II(36.79 cm and 33.42 cm),the transparency of both enperiments were in the suitable range(30-40 cm).Dissolved oxygen(DO)was in a high range(separation I 4.5-6.5mg/l,separation II 5.5-7mg/l),DO in November lowest Ex I 4.5mg/l and Ex II 5.5mg/l.In the experiments,p H range is 7-8.7,Ex II is 6-8.5,both of experiments were in the suitable range(6-8),Ex II p H was higher than Ex I.Salinity was 0ppt to 1ppt,salinity on average was less than 1ppt.The average water hardness was 51.35mg/l and 48.23 mg/l in the Ex I and II,so the water was soft water(0-60 mg/l).