Melanin concentrations in vendace (Coregonus albula) and whitefish (Coregonus lavaretus) larvae from five boreal lakes with different optical properties

The objective was to investigate correlation between melanin concentration in fish larvae and the optical properties of water in five study lakes. Melanin concentration was analyzed from vendace and whitefish larvae; sampled in May from lakes with different UV attenuation depth, water colour and transparency. Overall, vendace exhibited more pigmentation than whitefish. In both species larval pigmentation correlated positively with water colour, but the correlation was negative with UV-B attenuation depth. Based on our results, it is evident that ambient UV-B was insufficient to modify the degree of melanin pigmentation of coregonid fish larvae in Finnish lakes. We suggest that the main reason for the observed difference in larval melanin concentrations between lakes is that larvae adapt to the background colour, possibly to reduce visual predation.