Effect of different stocking size and density on artemia survival rate while copepod present

Abstract

Artemia culture helps people in Soc Trang province, especially Vinh Chau district to gain lots of profit. However, when the salinity of water is lower than the suitable range (80-100ppt), Artemia have to face with Copepod – their predator/competitor. It can cause the survival of Artemia decreases down to 0% within few days. This thesis had two parts. The 1st part was set up to confirm the impacts of Copepod on survival rate of Artemia. It included 2 kinds of samples that cultured Artemia with and without Copepod. The result of part 1 show that Copepod had the negative impact on Artemia survival. The survival rate of the samples within Copepod was very low (0%). So, the 2nd part need to be carried out to identify the stocking size and density of Artemia in which Artemia can overcome the impact of Copepod. The experiment in this part was co-culturing Artemia and Copepod in three different Artemia's densities (100, 150, 200 individual/L - correlate with D1, D2, D3), different starting-cultured size of Artemia (i.e. after 1 day - L1, 2 days - L2 and 3 days - L3, of hatching (DAH)) under two different water salinities (50ppt, 30ppt). Each treatment was replicated 3 times. After 3, 5 and 7 days of culture, the survival rate and length of Artemia in each sample were measured. Based on the collected data, it could be noticed that the starting-culture size affected survival rate of Artemia considerably in both 30ppt and 50ppt salinity, while the effect of cultural density was not clear. Under 30ppt, with the size L1 and L2, in all densities, survival rate was very low (lower than 5%) but with the size L3, it was high (higher than 80%). Under 50ppt, survival rate of Artemia in size L1 with density D1, D2 was low (lower than 5%) but with D3, it was acceptable (about 50%). While in the size L2, L3, all samples had the high survival rate (higher than 70%). Keywords: survival of Artemia different density different size low salinity Copepod