Optimization of harvested halibut by lowering maturation, increasing growth and improving flesh quality

The proposed project aims at optimizing conditions during the on-growing phase of Atlantic halibut and improving quality of the end product. The effect of photoperiod in combination with feed cycling on maturation, and the underlying endocrine mechanisms involved, will be thoroughly investigated. The approach is multifactorial, and aims at investigating and exploiting basic physiological mechanisms under various rearing conditions, while at the same time linking those mechanisms with fish growth performan ce and quality of the end product. The halibut industry has previously experienced problems maintaining colour, texture hardness and shelf life of halibut products. This could be linked to increased growth during summer, as preliminary studies displayed t hat unstarved fish became pale white, soft and had a shelf life of 1-2 weeks, whereas starved fish maintained its texture hardness and had a shelf life of 3-4 weeks. With the right strategy, we believe that these results could be utilized in the industry both in terms of increasing growth, reducing maturation and improving flesh quality, while at the same time reducing feed and labour costs. The proposed project will utilize different photoperiods in combination with new feeding regimes, i.e. exploiting c ycles of restricted rations and re-feeding in the commercial production of farmed halibut, to control growth, maturation, manipulate the final composition of the body tissues and improve growth efficiency. The project will investigate: - How fasting perio ds can initiate compensatory growth in halibut, and thus reduce feed and labour costs. - Control of maturation in halibut by manipulating photoperiods in combination with starvation periods. - The underlying endocrine mechanisms involved in the maturatio n process in response to the various treatments assigned. - The effect of feed cycling on biomass production in the on-growing phase of halibut, and how such starvation periods affects flesh quality.