Growth and survival studies of halibut (Hippoglossus hippoglossus L.) from hatching to beyond metamorphosis carried out in mesocosms

Abstract

To each of five floating plastic bags 1500 halibut larvae were transferred from the hatchery one day after hatching. The plastic bags had a volume of 11.5 m3, a total depth of 5.5 m and they were moored to floating collars. The bags were made of polyethylene coated with black PVC. Each bag was covered with a roof so the larvae were in a totally dark water column the first month. The general salinity was that of Atlantic water. Supplied water had a salinity of 30-32 o/oo. The halibut larvae reached the functional stage 40 days after hatching and natural zooplankton was added. At this time opening gradually was made in the roof of three of the bags while in two bags light was supplied by underwater lamps. Survival to the first feeding stage was about 45%. Almost all functional larvae started to feed, and they reached a size of 20 mm at metamorphosis and bag termination 45 days after first feeding was observed. The dry weight had increased from 600 to 3500 ug in the period of active feeding. The mean overall survival was 3.3%.