First feeding of Atlantic halibut ( Hippoglossus hippoglossus) using different combinations of Artemia and wild zooplankton

Abstract

Larvae of Atlantic halibut were offered different combinations of Artemia and wild Zooplankton during first feeding to examine the effects on feeding incidence, growth, survival and pigmentation. Free amino acid and fatty acid composition in feeds and fish larvae were also analysed. The free amino acid concentration in unenriched Artemia averaged 45 μmol/g w.w., compared to 116 μmol/ g w.w. in the wild Zooplankton. Super Selco ™ (Artemia Systems, Belgium)-enriched Artemia increased the concentration to 57 μmol/g w.w. on average, and also increased the lipid content in Artemia to approximately the levels found in wild Zooplankton (3.0% of wet weight), though with a much lower n − 3 PUFA content. Larvae fed 19 days on enriched Artemia (EA) were significantly larger than larvae fed wild Zooplankton (Z), wild Zooplankton for 7 days then unenriched Artemia (Z7) or unenriched Artemia (UA). The EA group also showed the best survival at day 19, 28.7% (19.9–34.4%) compared to 14.0% (13.2–14.7%) in the Z group and 13.6% (10.5–18.3%) in the Z7 group. Also the UA group had significantly higher survival 22.8% (18.8–25.5%) than the Z group, but showed slower growth. The fatty acid composition of larvae fed Artemia showed a development towards the composition of their feeds, while the fatty acid composition in the larvae fed wild Zooplankton remained relatively similar to that of prefed larvae. After 57 days of feeding, high frequencies of malpigmented juveniles were observed in the UA and EA groups (95.7 and 70.6%, respectively) as well as in the Z7 group (80.8%). All larvae fed wild Zooplankton or larvae transferred from an unenriched Artemia diet to a diet of wild Zooplankton from day 19 onwards, became normally pigmented. The present experiment showed that use of Artemia could be successful in providing growth and survival in the early larval stage of exogenous feeding in Atlantic halibut, but had negative effects on pigmentation later on. However, by introduction of wild Zooplankton prior to a critical stage (found to be beyond 19 days of feeding) these effects could be eliminated.