Requirements for carotenoids in fish diets

Carotenoids are among the most widespread and important pigment classes in living organisms, and in marine animals, astaxanthin is the most commonly occurring red carotenoid. Carotenoids are vitamin A precursors and are fundamental in photosynthesis and light protection in plants. Increasing attention has been drawn to a possible light protection, cancer prevention and immune enhancement by carotenoids in mammals. Reported functions in fish range from a general enhancement of performance to specific functions in reproduction and metabolism. In this paper, we show that astaxanthin is essential for growth and survival of fish and crawfish, and discuss this fact in relation to the use of purified and semipurified diets in nutritional studies. The similarity in action of astaxanthin and canthaxanthin compared to α-tocopherol (vitamin E) and retinol (vitamin A) suggests that these two carotenoids should be listed among the fat soluble vitamins.