| Abstract |
The breeding of bivalve larvae has up t o now always been conducted in closed systems. This method requires great care and consequently much labor. Using running water systems, we intended to exclude handling and avoid infestations and diseases without the use of antibiotics . Primarily, we used two cylindrical 20 m3 tanks, both with a filtering sand bottom and air-lift system. The flow was about 400 liters/hr. The temperature was 20 C. One tank was used as the filter, the second as our breeding unit in which circulation was maintained by adapted aeration. Newly released larvae of Ostrea edulis were introduced at four times. Larvae were fed daily at a rate of from 10 Isochrysis galbana, 10 Monochrysis lutheri and 2 Tetraselmis suecica per microliter to 25 I.g., 25 M. l. and 5 T.s. per microliter. The best results were obtained at the end of experiment using a stocking density of 220 larvae/liter . We observed a shorter larval period than usual records. Metamorphosis took place from day 9 to day 11. Five percent of the larvae were collected as spat on plates at an early stage (24 to 48 the hours), without considering the high numbet of spat settled on the tank itself. Total number of settled spat was about 15 to 20% of last larval density. These preliminary results need to be studied thoroughly. Nevertheless, the experiment shows that continuous oyster spat production ir feasible in running water systems. [NOT CONTROLLED OCR] |
