Cultured marine fish larvae are most often fed rotifers (Brachionus sp.) the first few weeks after first-feeding.
However the nutritional value of rotifers is generally inferior to the natural diet of marine fish larvae which is
comprised of zooplankton, mostly copepods. Commercial diets for rotifers vary considerably in nutrient composition
and this variation is partly mirrored in rotifers. The present study was undertaken to investigate the variation
in rotifers and rotifer diets used in commercial marine fish hatcheries and to identify possible deficiencies or
excess of individual nutrients. Culture and enrichment diets and unenriched and enriched rotifers were sampled
from four hatcheries for Ballan wrasse (Labrus bergylta) and analyzed for nutrients which can potentially fall outside
the safe window of supplementation for marine fish larvae. It is concluded that rotifer diets generally contain
appropriate levels of fatty acids and vitamins C and E, while vitamin A, iodine and selenium need more attention.
For vitamins D and K and many of the micro-minerals, data on larval requirements are still lacking and these
nutrients need further research. Protein and phospholipid levels are mainly determined by the rotifer's own
metabolism and can be low compared to assumed requirements.
Statement of relevance: