Effect Of Dissolved Oxygen, Salinity, Ammonia-N And Nitrite-N On The Survivoal And Food Intake Of Portunus Trituberculatus

In this study, the effects of dissolved oxygen, salinity, ammonia-N,nitrite-N and theinteractive effect of salinit and ammonia-N on the survival and food intake of Porrunustrituberculatus are investigated, all the results are as following.Under the conditions of salinity of30, temperature of27℃~30℃and pH7.5~8.5,experiments were conducted to identify the effect of DO (1mg/L、2mg/L、3mg/L、4mg/L、5mg/L、6mg/L) on the on the survival and food intake of Porrunus trituberculatus.. Theresults are as following: The DO cocentration is not suitable for Porrunus trituberculatusbelow2mg/L as it shows a low chance of survival and low food intake rate. Under the DOconcentration of4mg/L~6mg/L, the survival rate was100%,food intake rate was high, butsignificant difference was appeared at the DO concentration is1mg/L~3mg/L (p<0.05).The food intake rate of the DO cocentration of3mg/L was higher than the DOconcentration of1mg/L~2mg/L，lower than the OD concentration of4mg/L~6mg/L,andthere was significant difference with them (p<0.05). The results suggest that the DOconcentration of below2mg/L is not suitable for Porrunus trituberculatus. The DOcocentration of3mg/L was high survival rate,but the food intake rate is not high, thevitality is weak.The DO cocentration of4mg/~6mg/L is suitable for crab,as it shows highfood intake rate and strong vitality.Under the conditions of temperature of26℃~30℃, pH7.5-8.5and DO>5.5mg/L, Thesurvival rate, food intake of Porrunus trituberculatus. Under acute and gradual changesinsalinities were deter mined to evaluate the tolerance Swimming crab to salinity. Theabrupt changes insalinity mean that the salinity was changed to0,5,10,15,20,25,35,40,45,50and55from30.Respectively. The gradual changes insalinity mean that the salinitywas reduced and raised5every day for six days from30.The results are as following:Withthe acute salinity change, the survival rate of Porrunus trituberculatus was the highest atsalinity levels15~40which had a significant difference with salinity levels10and belowor50and above (p<0.05),while had not significant difference with salinity45(p>0.05).Thesurvival time of Porrunus trituberculatus were the longest at salinity levels15~40which had significant difference with other group (p<0.05).At salinity levels30~35, swimminghad high food intake rate. There was significant difference with other group (p<0.05).Food intake rate of the salinity of25is after the salinity levels30~35. There wassignificant difference with salinity levels10below and50above(p<0.05). With a gradualsalinity change, the survival rate of Porrunus trituberculatus was high at salinity levels15~45which had significant difference with salinity levels0and above50(p<0.05), Thereis high survival time at salinity levels15~45which had significant difference with salinitylevels above50and below5(p<0.05), but no significant difference with salinity levels10(p>0.05). The crabs had the highest food intake rate best at salinity30which had nosignificant difference with salinity levels35(p>0.05),but had significant difference withothers (p<0.05),the food intake rate of salinity levels25and35after salinity levels30,thereis significant difference with othr group. Crab could better acclimatize themselves togradual change than acute change salinities. The results suggest that the most suitable forcrab food intake is at salinity30~35.salinity levels above50or5and below is not suitablefor food intake.Under the conditions of salinity of30, temperature of26℃~30℃, pH7.5~8.5andDO>5.5mg/L, experiments were conducted to identify the effect of ammonia-N(0mg/L,5mg/L,10mg/L,20mg/L,40mg/L,80mg/L and160mg/L) on the survival and foodintake of Porrunus trituberculatus. The results are as following:Porrunus trituberculatusshow high survivorship,survival time and food intake rate under the concentration ofammonia-N0mg/L~40mg/L which had significant difference with high concentrationgroup of ammonia-N (80mg/L~160mg/L)(p<0.05), the food intake rate of the ammonia-N0mg/L has significant difference with the groups of above5mg/L (p<0.05),at theammonia-N concentration of5mg/L,the crab shows strong vitality.The result suggests thatthe optimal concentration of ammonia-N for Porrunus trituberculatus to survive and tofood intake is0mg/L~5mg/L.Under the conditions of salinity of30, temperature of26℃~30℃, pH7.5~8.5and DODO>5.5mg/L,experiments were conducted to identify the effect of nitrite-N(0mg/L,10mg/L,20mg/L,40mg/L,80mg/L,160mg/L and320mg/L) on the survival and foodintake of Porrunus trituberculatus. The results show that: The best condition for foodintake and survival was at the concentration of nitrite0mg/L~40mg/L,which hadsignificant difference with other groups (p<0.05). There was hight food intake rate atnitrite-N0mg/L~10mg/L,which had significant difference with other groups (p<0.05). Theresult suggests that the optimal concentration of nitrite-N for Porrunus trituberculatus tosurvive and to have a positive food intake rate is0mg/L~10mg/L. Under the conditions of salinity of30, temperature of27℃~30℃, pH7.5~8.5and DOof5.5mg/L~6.0mg/L, experiments were conducted to identify the interactive effect ofsalinity(20、30、40) and ammonia-N(1mg/L、5mg/L、25mg/L) on food intake of Porrunustrituberculatus. The results are as following: the interaction effect is remarkable(p<0.05).