Abstract:

The cultivation techniques of the marine cold water species turbot (Scophthalmus maximus), Atlantic halibut (Hippoglossus hippoglossus) and Atlantic cod (Gadus morhua) have been developed in Norway during the last decade. Research programs have been undertaken to establish the scientific basis for a commercial, feasible juvenile production technology. The Atlantic halibut must be carefully maintained in flow through silo systems during their prolonged critical yolk sac stage (30 days). The period of first feeding lasts for approximately 80 days, and copepods and Artemia are in most cases used as live feed. The halibut larvae have high requirements for n-3 HUFA, in particular DNA. More efficient enrichment techniques for Artemia and more reliable first feeding technology are still major challenges for this species. Commercial production of halibut is still in its early phase, but the numbers produced have increased steadily during the last few years, with the exception for 1995. The number of weaned halibut fry transferred to the growout phase was approximately 370 000 in 1994 and less than 100 000 in 1995. The production costs range between 5-6 US$ per fry. The rearing technology for juvenile turbot is well established. Turbot larvae are cultured using classical intensive rearing techniques with microalgae, rotifers and Artemia as live feed. The larval densities are kept rather low by commercial producers (<5 1(-1)), but densities in research projects are normally much higher (<100 larvae per litre). The survival through the larval stage is normally both predictable and relatively high (10-50%). Improvements in fry quality, e.g. growth potential and viability, are higher priorities than improvement in survival. The number of fry produced in Europe in 1995 was some 2.5 million, and depended on fry requirements rather than technical constraints. Production costs range between 1.3-1.4 US$ per fry.The rearing technology of Atlantic cod is similar to that of turbot, but the dietary requirements of cod, as well as most research objectives, are comparable to those of halibut. Cod, however, currently has a limited commercial potential. The number of cod juveniles produced in 1995 was approximately 300 000, all produced in poll systems as part of restocking projects. Established hatchery techniques may be utilized for commercial production of cod juveniles if the production costs of cultivated cod is lower than the price obtained for wild caught cod.
(Norwegian Univ. Sci. and Technol., Trondheim Biol. Stn., Bynesveien 46, N-7018 Trondheim, Norway)
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