Effects of Water Exchange Rate on the Juvenile Survival and Growth of the Rockworm Marphysa sanguinea (Polychaeta: Eunicidae)

The rockworm, Marphysa sanguinea is the most well known polychaete species with a high economic value. However, this species has a high mortality from the larval stage to the juvenile stage. The purpose of this study was to evaluate to confirm optimum rearing water exchanges that affect survival and growth rates of rockworm juvenile. Juveniles were maintained in five different water exchange rates: no water exchange, one cycle/day, two cycles/day, three cycles/day and continuous exchange (one cycle means that whole water in a tank is replaced by new water one time a day). Each trial was conducted in triplicate for two months. Results showed that, three cycles/day was the most efficient, although the continuous exchange showed the highest survival rate.