Fish habitats can deteriorate due to the effects of a range of detrimental or toxic substances which humans discharge into the environment either intentionally, under licence (pesticides and discharges of waste), or unintentionally (accidents). Some discharges have a local effect, while the others, such as global warming, have a global one. Breaking up the soil, such as ditching of sulphate soils, can lead to deterioration in water quality and increase the concentration of metals in water.
Discharges of environmental toxicants have reduced
Discharges of environmental toxicants have been successfully reduced. The concentrations of compounds (dioxin, PCBs, etc.) in fish have reduced to a third or even more of their highest concentrations. However, the downward trend in toxicant concentrations has bottomed out and new compounds have been detected.
In rainbow trout and other farmed fish the concentrations of environmental toxicants are small, since feed is subject to strict limit values in order to protect consumers.
In fish caught from inland waters, such as vendace, and in low-fat fish in the Baltic Sea, the concentrations of PCB or dioxin are not exceedingly high, since organic halogen compounds largely accumulate in fat-rich fish in the Baltic Sea. The highest concentrations have been found in Baltic Sea salmon, in which compounds from fat-rich prey fish such as sprat, Baltic herring and three-spined stickleback accumulate.
Fish consumption should be increased in line with dietary recommendations
Environmental toxicants reduce the value of only some fish species used as food for humans and raw material for animals. In most fish species, the concentrations of environmental toxicants are small. Fish are an excellent source of protein and beneficial omega-3 fatty acids, and the authorities recommend that fish consumption as a foodstuff should be increased. However, account should also be taken of the food consumption recommendations issued by the Finnish Food Authority Evira. The health benefits of even fat-rich Baltic fish outweigh the possible disadvantages due to environmental toxicants contained in fish, particularly for people past middle age.
Luke is engaged in research on oil spills and chemical accidents
In collaboration with other actors, the Natural Resources Institute Finland (Luke) is engaged in research on detrimental substances. Luke is charged with obtaining fish samples and determining the age and other biological characteristics of sample fish. Luke is also one of the authorities involved in researching the impact of oil spills and chemical accidents.
Knowledge of the impact on fish of detrimental substances and changes in the aquatic environment on fish is required for decision-making on the fishery sector and the management of fishing waters. Data on concentrations of environmental toxicants and other detrimental substances is needed when assessing the situation in Finland in relation to the EU’s highest allowable concentrations of environmental toxicants in food and feed and other, similar maximum limits.
Picture on top of the page: Esa Lehtonen