Mineral requirements of Atlantic cod (Gadus morhua) larvae at first-feeding

Production of Atlantic cod has increased sharply in recent years, but production of juveniles is still a bottleneck in the production line, because juveniles of good quality have a great impact on the success in ongrowing, and because the present knowledg e is insufficient for optimal intensive juvenile production. Marine fish larvae hatch at an immature stage and most species require specially adapted rearing methods and diets at first-feeding. In nature, marine fish larvae feed mainly on copepods, while in intensive hatcheries, Atlantic cod are fed rotifers the first month after first-feeding. The fatty acid composition and vitamin levels in rotifers are quite well managed by the industry. However, minerals have been given little attention, both in resea rch and commercial culture. We do not know the actual requirements of minerals in marine fish larvae. It is assumed that fish larvae generally have higher requirements than larger fish, due to their high growth rates and the expenses connected with ontoge ny and metamorphosis. It is also possible that fish larvae have adapted to their very nutritious natural feed. However, the nutrient levels in copepods vary and the actual requirements of the larvae may be lower than the levels found in copepods. This pro ject will therefore be to determine the requirements of selected minerals in cod larvae.