Feeding marine fish larvae with lipid sources alternative to fish oil

Abstract

Despite global production of fish oil has been stagnant for the last decade, its demand as a source of n-3 PUFAs for aquafeeds has been continuously increasing. In marine fish larvae, fish oil replacement levels by vegetable oils will depend on the use of live preys or microdiets. The high content of lipids in enrichments for live preys may allow a high percentage of fish oil substitution, depending on the requirements of each species but also on the utilization of enrichment lipids by rotifers or Artemia. In microdiets, despite larvae have high EFA requirements, the high protein at this stage of development impose high dietary protein contents which in turn provide additional sources of EFA. Complete substitution of fish oil by vegetable oils in enrichments for seabream larvae reduces growth and affects larval normal behaviour. But fish oil replacement by vegetable oils in microdiets for seabream, did not affected growth and survival. Moreover, feeding larvae with vegetable oils increased up to 6 times the relative expression of delta 6 desaturase like gene in larvae fed rapeseed and soybean oils. Since the lack of essential fatty acids for marine fish constrains the use of vegetable oils in larval feeds, alternative EFA sources are being developed, such as marine micro algae which constitute a well recognized “single cell oil source” high in PUFA. Substitution of either fish oil or booster oils in microdiets for seabream by homogenized C. cohnii promotes good growth and survival, particularly in very young larvae, whereas substitution by Phaeodactilum tricornutum at this larval stage damages intestine epithelia and reduces survival. Finally, substitution by Schyzotrichium sp. slightly reduces larval seabream growth.