As recently as the 1950s and 1960s relatively large deliberate oil discharges from ships were common in the Baltic (Ahnhoff and Johnsson, 1977, ICES/SCOR, 1977), causing the deaths of thousands of seabirds in the archipelago of south-western Finland and in the Baltic itself. Since then international agreements, enlightment and oil pollution control have diminished oil discharges. The regulations of the 1974 Convention on the Protection of the Marine Environment of the Baltic Sea Area (the Helsinki Convention) were particularly effective in this respect, even before they came into force in 1980.