VITAMIN-B-6 IN ATLANTIC HALIBUT, HIPPOGLOSSUS-HIPPOGLOSSUS - ENDOGENOUS UTILIZATION AND RETENTION IN LARVAE FED NATURAL ZOOPLANKTON

A single batch of Atlantic halibut larvae was reared in floating plast ic enclosures, offered natural plankton collected from a lagoon and sa mpled regularly for measurements of vitamin B-6. At hatching individua l whale larvae contained 9.0 +/- 0.2 ng of vitamin B-6, of which 95% w as present in the yolk. At the onset of first feeding 50% of the vitam in B-6 present in the yolk at hatching had been transferred to the lar val body. There was a relatively constant weight specific content of v itamin B-6 in the larval body from hatching until first feeding at 206 Day degrees post hatch (D degrees PH) at 3.5 +/- 0.3 mu g g(-1) DW. D uring this period there was a net decline of 2.3 ng vitamin B-6 per la rvae. After onset of first feeding the vitamin B-6 content in the larv ae continued to decline and reached its lowest level at 300 D degrees PH with 5.0 ng individual(-1). With continued development the feeding larvae increased their content of vitamin B-6. However, in weight spec ific terms the content of vitamin B-6 in halibut larvae above a DW wei ght of 5 mg stabilized at 5.1 +/- 0.2 mu g g(-1) DW, about the same va lue as the plankton feed offered. The data in this study represents vi tamin B-6 status in halibut larvae and planktonic prey in semi-intensi ve culture systems with a high outcome of metamorphosed larvae and may therefore serve as a basis for feed formulation in intensive farming of Atlantic halibut. (C) 1997 Elsevier Science B.V.