Abstract:

Weaning of pikeperch (Sander lucioperca L.) larvae and the importance of highly unsaturated fatty acids was examined in two consecutive experiments. In the first experiment, 16day old larvae (wetweight:5mg; dryweight:0.82mg; length:9.52mm) were reared in 10-1 cylindrical- conical tanks in a recirculating system (20±l° C) at a stocking density of 60 larvae litre 1 and fed either enriched Artemia or non enriched Artemia nauplii for 10 consecutive days. Enrichment was achieved with either DHA selco® or ICES 30/0.6 emulsions. Larval growth was similar for all treatments, with the best growth (mean wet weight: 55.1±20.8mg) obtained by fish larvae fed DHA enriched Artemia nauplii and the lowest growth (wet weight: 16.7±10.3mg) in fish fed non enriched Artemia nauplii. The specific growth rate ranged between 19.2±2.0 - 24.0±2.0%day while survival rate ranged between 6.8±0.7 - 8.0±0.7 with larvae fed on DHA enriched Artemia and EPA enriched Artemia respectively. FAME composition in larvae at 26 days post hatch (dph) was similar although larvae fed DHA enriched Artemia had the highest FAME content (94.3mg.gDW1) and the lowest FAME content was (84.8mg.gDW1) for those that received non enriched Artemia nauplii. In the second experiment, 26 day old larvae obtained from experiment! were reared under similar culture conditions but at a lower stocking density of 9 larvae litre and were fed exclusively with artificial feed (AgloNorse®, O-Range® and Vegetable test diet), under five treatments (DHA- AgloNorse® (DHA-A),DHA- O-Range® (DHA-O),DHA Vegetable (DHA-V),EPA- AgloNorse® (EPA-A),NON- Vegetable (NON-V)) for a period of 13 days. Significant differences were observed in larvae that received DHA-A and NON-V and DHA-0 treatments while those under EPA-A and DHA-V seemed non-significant. The best growth (wet weight: 103.2±7.3mg) and lowest growth (wet weight: 52.1±15.7mg) was obtained by fish larvae that received DHA-A and NON-V treatments respectively. Larvae that received dietary HUFAs (DHA-A, EPA-A and DHA-O) throughout the experimental period had the highest DHA and EPA levels, between 17.9 - 22.3mg.gDW and 5.0 - 5.3mg.gDW respectively. When exposed to stress by confinement in 21-beakers with either culture water or saline water (15ppt), larvae at 26dph expressed more cortisol than larvae at 39dph.