The M74 syndrome of baltic salmon ( Salmo salar) and organochlorine concentrations in the muscle of female salmon

Abstract

Organochlorine concentrations in the muscle of female Baltic salmon ( Salmo salar), ascending for spawning in the Simojoki River on the north-eastern coast of the Gulf of Bothnia from 1988 to 1992 are given in this paper in relation to reproduction success, monitored as viability of offspring. In spring 1992 and 1993 all the yolk-sac fry of 52 % and 75 % of the females, sampled in autumns 1991 and 1992 respectively, died due to the M74 syndrome, i.e., heavy mortality of yolk-sac fry (YSM). The TEOs of the most frequently detected polychlorinated dibenzofurans (PCDFs: 1,2,3,7,8-PeCDF, 2,3,4,7,8-PeCDF and 2,3,7,8-TeCDF) and those of coplanar PCBs (CB77, CB126 and CB169) were about twice as high in 1991 and 1992 than before; these substances either showed a significantly increasing time trend or then none at all. The principal component analysis (PCA) showed a strong connection between YSM and the contents of these toxic congeners. PCA also indicated a strong negative connection with YSM and the orange colour intensity of eggs and a weak positive connection with YSM and oxychlordane, hexachlorobenzene and 2,3′,4,4′5-pentachlorodiphenyl ether. The PCA results were supported by the observed significant negative Pearson correlations between egg colour and the contents of toxic PCBs and PCDFs as well as between egg colour and YSM. These compounds seemed not to have any connection to early embryonal mortality, whereas total PCB and DDT concentrations did show an association to that.