Do carp larvae require vitamin C?

Two experiments were conducted on common carp ( Cyprinus carpio L.) larvae and juveniles. In the first, larvae were fed experimental flaked diets during an initial period of 11 days at a water temperature of 26°C. Different diets based on yeast and liver resulted in insignificant differences in individual body weight of fish which also were significantly smaller (6.5–8.8 mg) than fish fed live Artemia nauplii (33.2 mg). Fish fed dry diets displayed significantly higher mortality (7.8–56.2%) than fish fed live food (0.6%), the former groups showing signs of vitamin deficiency manifested by caudal fin erosion and deformation of gill arches. Total ascorbate and dehydroascorbate were analysed in both fish and diets. Total ascorbate concentrations in whole fish were significantly lower in the groups fed dry diets (16.5–36.9 μg g −1 wet weight) than in the groups fed Artemia (101.1 μg g −1). On average, dehydroascorbate constituted 74% and 55.2% of total ascorbate in fish fed dry diets and live Artemia, respectively. In the second experiment 33-mg juveniles previously fed Artemia were offered the same dry diets and this treatment resulted in 5.5-fold body weight increments within 16 days. Total ascorbate content in fish varied from 39.3 to 62.3 μg g −1, but the reduced ascorbic acid constituted a much higher proportion (37.8–52.5%) than in larval carp. It seems that common carp larvae require vitamin C, which is the opposite of what has been reported for juveniles and adults of this species.