Participating organizations (WP leader in bold): P7. IMR, P17. NIFES and P22. SWH
Task 17.1 Recirculation (RAS) vs Flow through (FT) systems during yolk sac and first feeding stages and the effects on larval survival, quality and growth. The commercial production of halibut fry is currently carried out in flow through systems (FT), while there is a growing consensus that RAS would offer more stable environmental and chemical water parameters that would lead to improved larval performance. A RAS system will be constructed from three generally used first-feeding tanks and compared to the classic FT system, both during the yolk sac stage and during first feeding. Larvae will be evaluated in terms of growth, survival and larval quality in terms of pigmentation and eye migration success. It is not clear whether the intestinal microflora of halibut larvae is determined by the feed or by water quality parameters. In order to elucidate this, samples will be taken for examination of gut morphology and bacterial flora. The results will give information on at what stage, and how the intestine is colonised, and will form the basis for the implementation of probiotics in the industrial protocol to be developed in Task 17.2.
Task 17.2 The effect of probiotics on larval microbiota and survival and development of an industrial protocol . The aim of this task is to clarify which bacteria are capable of both controlling pathogens and improve survival of halibut larvae. These trials will be modeled from protocols already published with cod (Gadus morhua) larvae, but adapted to halibut. The exceptionally long yolk sac stage of halibut and the critical early feeding stages make the application of probiotics during the early life stages of halibut particularly important. Probiotic trials will be based on the multiwell trials with cod yolk sac larvae and on the gnotobiotic protocos for European sea bass developed. These techniques will be adapted to the longer yolk sac stage and the larger size of Atlantic halibut yolk sac larvae, in accordance with the challenge experiments with cod, halibut and turbot (Scophthalmus maximus). Multiwell trials imply a high number of replicates (n=50-100) with one larva in each well, giving statistical robustness and high experimental control. The bacteria will primarily be from the Roseobacter/ Ruegeria/ Phaeobacter group, which have been shown to possess probiotic properties, including TDA production. Based on the results obtained by the in vitro trials, and the information obtained in task 17.1, a full scale trial will be performed in triplicate tanks, comparing RAS and FT systems and where probiotics are distributed either through addition to the water or via the feed. A protocol for industrial use of probiotics in Atlantic halibut juvenile production will be developed based on the results of this full-scale experiment.
Task 17.3 Production of on-grown Artemia. At present, halibut larvae are fed Artemia nauplii through the whole first feeding period. An observed reduction in growth rate during the later phases of first feeding indicates that this feed is insufficient to maintain high growth. A larger prey size, with a higher nutrient content may be a more appropriate choice for those stages. Therefore, a production protocol for on-grown Artemia will be further developed, where water renewal and quality are crucial parameters. This protocol includes feeding, washing and disinfection of the Artemia, and will be tested both in experimental and commercial scale. These experiments will be followed by analyses of bacterial activity. The biochemical profile of macro and micro nutrients of the on-grown Artemia compared to Artemia nauplii at the research facility and at the commercial hatchery will be analyzed in WP 11 Nutrition – Atlantic halibut.
Task 17.4 Comparison of feeding on-grown Artemia versus Artemia nauplii on larval performance . Atlantic halibut larvae will be fed Artemia nauplii from first feeding. At 20 days post first feeding (dpff) one group of larvae will be fed on-grown Artemia whereas the other group will continue to be fed nauplii. The experiment will last until 70 dpff, when the halibut larvae have completed metamorphosis. Growth, survival and juvenile quality will be measured, including GI microflora, behavior, pigmentation, eye migration and histological characterization of selected organs, including the intestine. Nutrient analyses of samples taken in this trial and characterization of the digestive physiology of the larvae will be carried out within WP 11 Nutrition – Atlantic halibut.
Task 17.1 Recirculation (RAS) vs Flow through (FT) systems during yolk sac and first feeding stages and the effects on larval survival, quality and growth. The commercial production of halibut fry is currently carried out in flow through systems (FT), while there is a growing consensus that RAS would offer more stable environmental and chemical water parameters that would lead to improved larval performance. A RAS system will be constructed from three generally used first-feeding tanks and compared to the classic FT system, both during the yolk sac stage and during first feeding. Larvae will be evaluated in terms of growth, survival and larval quality in terms of pigmentation and eye migration success. It is not clear whether the intestinal microflora of halibut larvae is determined by the feed or by water quality parameters. In order to elucidate this, samples will be taken for examination of gut morphology and bacterial flora. The results will give information on at what stage, and how the intestine is colonised, and will form the basis for the implementation of probiotics in the industrial protocol to be developed in Task 17.2.
Task 17.2 The effect of probiotics on larval microbiota and survival and development of an industrial protocol . The aim of this task is to clarify which bacteria are capable of both controlling pathogens and improve survival of halibut larvae. These trials will be modeled from protocols already published with cod (Gadus morhua) larvae, but adapted to halibut. The exceptionally long yolk sac stage of halibut and the critical early feeding stages make the application of probiotics during the early life stages of halibut particularly important. Probiotic trials will be based on the multiwell trials with cod yolk sac larvae and on the gnotobiotic protocos for European sea bass developed. These techniques will be adapted to the longer yolk sac stage and the larger size of Atlantic halibut yolk sac larvae, in accordance with the challenge experiments with cod, halibut and turbot (Scophthalmus maximus). Multiwell trials imply a high number of replicates (n=50-100) with one larva in each well, giving statistical robustness and high experimental control. The bacteria will primarily be from the Roseobacter/ Ruegeria/ Phaeobacter group, which have been shown to possess probiotic properties, including TDA production. Based on the results obtained by the in vitro trials, and the information obtained in task 17.1, a full scale trial will be performed in triplicate tanks, comparing RAS and FT systems and where probiotics are distributed either through addition to the water or via the feed. A protocol for industrial use of probiotics in Atlantic halibut juvenile production will be developed based on the results of this full-scale experiment.
Task 17.3 Production of on-grown Artemia. At present, halibut larvae are fed Artemia nauplii through the whole first feeding period. An observed reduction in growth rate during the later phases of first feeding indicates that this feed is insufficient to maintain high growth. A larger prey size, with a higher nutrient content may be a more appropriate choice for those stages. Therefore, a production protocol for on-grown Artemia will be further developed, where water renewal and quality are crucial parameters. This protocol includes feeding, washing and disinfection of the Artemia, and will be tested both in experimental and commercial scale. These experiments will be followed by analyses of bacterial activity. The biochemical profile of macro and micro nutrients of the on-grown Artemia compared to Artemia nauplii at the research facility and at the commercial hatchery will be analyzed in WP 11 Nutrition – Atlantic halibut.
Task 17.4 Comparison of feeding on-grown Artemia versus Artemia nauplii on larval performance . Atlantic halibut larvae will be fed Artemia nauplii from first feeding. At 20 days post first feeding (dpff) one group of larvae will be fed on-grown Artemia whereas the other group will continue to be fed nauplii. The experiment will last until 70 dpff, when the halibut larvae have completed metamorphosis. Growth, survival and juvenile quality will be measured, including GI microflora, behavior, pigmentation, eye migration and histological characterization of selected organs, including the intestine. Nutrient analyses of samples taken in this trial and characterization of the digestive physiology of the larvae will be carried out within WP 11 Nutrition – Atlantic halibut.
