THE USE OF MALFORMATIONS IN PELAGIC FISH EMBRYOS FOR POLLUTION ASSESSMENT

Malformations in fish embryos have been monitored for several years in the southern part of the North Sea. Their occurrence was thought to b e related to pollution because malformation rates were highest in coas tal waters, known to receive high pollution loads. For the embryos of all species synchronous trends for the fluctuation of the occurrence o f malformations over time were registered in the areas covered, with i ntermediate prevalences at the beginning of the studies in 1984 and ma xima in 1987. Thereafter, malformations in all species decreased signi ficantly, followed by an abrupt increase in 1996. It was found that in addition to a close correlation between the concentrations of environ mental pollutants in the water and in the fish a significant negative correlation existed between surface water temperature and the occurren ce of malformed embryos of dab (Limanda limanda). These same correlati ons were also observed for other fish species over time and space. Thi s temperature-related correlation became increasingly visible with dec reasing concentrations of organochlorines in fish. From these findings it is concluded that aside from environmental pollutants, natural fac tors such as temperature may predispose developing fish embryos to the impact of pollutants.