Organochlorines And Thiamine In Salmon (Salmo Salar L.) And Prey Species, Baltic Herring (Clupea Harengus L.) And Sprat (Sprattus Sprattus (L.)), In Connection With The M74 Syndrome

No abstracts are to be cited without prior reference to the author.

Yolk-sac fry mortality in salmon from the River Simojoki emptying into the north­eastern Gulf ofBothnia, northern Baltic Sea, has been monitored and female muscle organochlorine (OC) and egg thiamine concentrations analysed in samples from certain years. OC and thiamine contents in the salmon prey species, Baltic herring and sprat, from the years of high M74 incidence have also been analysed. The proportion of females producing yolk-sac fry with M74 mortality has fluctuated in the period 1991/92 - 1998/99 from 31 to 92% and the mean annual yolk-sac fry mortality from 19 to 76%. OCs, especially dioxin-like ones in female muscle, increased at the same time as the M74 mortality. Salmon egg thiamine concentration correlated negatively with the M74 mortality of the respective yolk-sac fry. Baltic herring and sprat caught from late autumn to early winter contained thiamine, 8.6, and 6.9 nmol g-1, respectively. Concentrations of total PCB and PCDD increased in herring and sprat with age, and the levels of cdplanar PCBs and PCDFs were in all age groups of sprat two to three times as high as in herring. In salmon the coplanar PCB and PCDF concentrations were two to four times as high as in sprat and three to nine times as high as in herring calculated on either the fresh or lipid weight basis. It is concluded that the supply of thiamine for salmon from its main prey species, herring and sprat, has been adequate at least for growth, and that sprat might have been an important source of coplanar PCBs and PCDFs for salmon.