Effects of a possible oil spill on fish and fisheries of the Baltic Sea

This review deals with the toxic effects of oil and oil components on fish and the effects of potential oil spills on fish stocks, fishing and aquaculture. The aim is to enable better preparation to evaluate the short- and long-term effects of possible oil spills in the Baltic Sea.

The Baltic Sea is very sensitive to disturbances, and its natural environment is at risk from increasing levels of shipping and oil transportation. An extensive oil spill could cause serious consequences to the natural environment of the Baltic and also to the natural resources and fisheries of the surrounding states. In water, oil spreads or evaporates or it can form a resistant mixture or emulsion with water. Many factors, such as the physical and chemical properties of the oil, the season, the weather and sea conditions and the oil spill area, affect the behaviour of oil.

In addition to crude oil, light- and heavy-oil products are transported in the Gulf of Finland, and ships contain varying amounts of bunker oil. Depending on its origin, the composition and properties of crude oil vary greatly. Crude oil comprises mixtures of hydrocarbons, such as alkanes and aromatic hydrocarbons. Crude oil is industrially refined into light-oil products, such as petrol and diesel.

Heavy fuel oil is the remaining product of the refining process. Oil compounds have acute and sublethal effects on fish. Polycyclic aromatic hydrocarbons (PAH) of oil have mutagenic, carcinogenic and harmful physiological (immunological, endocrine-re- lated and osmoregulative) effects. The early developmental phases of fish are particularly sen- sitive to the effects of oil compounds. In adult fish, PAHs have effects on metabolism, growth and reproduction. Exposure to PAHs can lead to changes in the size of fish stocks and impact on the whole community of the Baltic Sea. As a consequence of an oil spill in the sea, econom- ic losses for fishermen and aquaculture are possible because of: fish acquiring an off-taste and taint; a decrease in fish stocks; and, obstacles and difficulties in carrying out the profession.

The safest and cheapest means to avoid the serious consequences of a big oil spill is to prevent one from happening. Various surveillance systems and agreements, such as the automatic iden- tification system (AIS) of vessels, and obligatory registration systems plus structural changes to vessels, such as a double hull, have improved the safety of vessels and oil transportation. In order to be able to estimate the effects of an oil spill on fish and fish stocks and the recovery from such an incident, extensive biological information about the initial state is needed.