Accelerated production of Atlantic halibut

This project aims at establishing optimal rearing conditions for maximal growth in the land-based phase of Atlantic halibut production. Environmental parameters (temperature, photoperiod and their interaction) will be manipulated to enhance faster growth in juveniles. Water quality experiments will focus on the effects of ammonia on growth in fish. This project will aim at identifying critical threshold limits of unionised ammonia that will reduce growth in different size classes of fish, thus providing f armers with a protocol for sustained control of this parameter in the land based phase. A sustainable production of Atlantic halibut will be dependent on a year-round supply of juveniles reared in intensive land-based systems at high densities. To effecti vely exploit such systems it is necessary to obtain detailed knowledge on the impact of key rearing on growth performance, food conversion efficiency and fish welfare. The current proposal will, through a series of large- and laboratory-scale experiments, provide the halibut aquaculture industry with a strategy that will significantly improve growth, reduce maturation, improve fish welfare and define the impact of a critical water quality parameter. The project will investigate the: - Optimal temperature s for growth throughout the land-based phase - Production advantages of step-wise temperature regulation as compared to a constant temperature regime - Potential benefits on growth from using extended photoperiods - Potential effects of environmental man ipulations in the early juvenile phase on subsequent growth and maturation in the commercial ongrowing phase in sea cages - Water quality requirements of juvenile halibut reared at high densities. - Eye status (cataract and cornea damages) and histidine i n fish muscle and lens will be analyzed under critical rearing conditions and experimental setup linked to culture conditions.