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\ntransferred 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\nwere moored to floating collars. The bags were made of polyethylene\ncoated with black PVC. Each bag was covered with a roof so the\nlarvae were in a totally dark water column the first month.\nThe general salinity was that of Atlantic water. Supplied water had a salinity of 30-32 o/oo. The halibut larvae reached the\nfunctional stage 40 days after hatching and natural zooplankton\nwas added. At this time opening gradually was made in the roof\nof three of the bags while in two bags light was supplied by\nunderwater lamps. Survival to the first feeding stage was about\n45%. Almost all functional larvae started to feed, and they\nreached a size of 20 mm at metamorphosis and bag termination\n45 days after first feeding was observed. The dry weight had\nincreased from 600 to 3500 ug in the period of active feeding.\nThe mean overall survival was 3.3%.