Sensitivity of different early developmental periods of Baltic herring (Clupea harengus) to water-accommodated fraction of crude oil

The probability for the oil accident to occur at the Gulf of Finland has been increasing last ten years and it is predicted to continue so. The risk is high based on the accident probability and the probable harm caused; some spawning areas of the Baltic herring (Clupea harengus membras) are located in the vicinity of ports and ship fairways with heavy traffic, so any oil spillage there could affect recruitment of this commercially important species. In this study, newly fertilized embryos, the older embryos and the hatched larvae of Baltic herring were exposed to water-accommodated fraction (WAF) made from crude oil. Oil exposure increased most the mortality of the hatched larvae, and larvae hatched during the exposure were more sensitive to the impacts of oil than larvae which were exposed after their hatching. The LC50 value was 16 % of WAF-solution of crude oil for the exposed larvae. The most tolerant for the oil were the embryos in late embryonic stage (the LC50 was 44 % of WAF-solution). During the exposure, some malformations i.e. a curving of the notochord were noticed.