Local and seasonal influences on the large scale production method for penaeid shrimp larvae.

Abstract

The authors established the large scale production method for larval penaeid shrimp at Aio in the Seto Inland Sea in 1964. Using the same method, further experiments on the hatch-ing and rearing of Kuruma shrimp (Penaeus japonicus) were conducted at Kumihama in a lagoon site and at Yamakawa in a partially-open sea site. At the lagoon site both the hatching and survival rates were poor due to the combined effect of using stagnant lagoon water for hatching and a dominant propagation of unfavorable protozoa beginning at the advanced zoea stage. In the partially-open sea site a better hatching rate was obtained. However, survival rate was poorer due to the fact that useful diatoms for propagation were scarce in the open sea water. Although the survival rate is influenced by local conditions, this method is more ef-ficient for mass production of postlarval shrimp. A better survival rate of 20-30% was obtained by using this method as compared to that of 3.5% by the conventional method. One disadvantage found in this method is a depression of growth in postlarval shrimp due to the high density of survivors in the tank. Daily body weight increases of 0.5-0.8 mg and conversion factors of 10-12 were obtained by this method.