Comparative studies on the group increasing of egg-carrying and free-spawning copepods

Group increasing of free-spawning copepod Acartia pacifica and egg-carrying copepod Schmackeria dubia in a semi-closed pond and the tanks in laboratory were compared. The results indicated that reproduction rate of A. pacifica was higher in stiring water than in still water, while S. dubia exhibited active multiplication under both conditions. Low nauplii production of A. pacifica in still water should be attributed to low hatching rate of the disperse eggs after they sink to bottom. Eggs of S. dubia, on the contrary, would be protected by the egg sacs and avoid the harsh bottom environment, then this egg-carrying copepod can yield high density of nauplii in still water also. Our results imply egg-carrying copepods are more applicable to rear for larvae culture than free-spawning copepods.