The use of malformations in pelagic fish embryos for pollution assessment

Abstract

Malformations in fish embryos have been monitored for several years in the southern part of the North Sea. Their occurrence was thought to be related to pollution because malformation rates were highest in coastal waters, known to receive high pollution loads. For the embryos of all species synchronous trends for the fluctuation of the occurrence of malformations over time were registered in the areas covered, with intermediate prevalences at the beginning of the studies in 1984 and maxima in 1987. Thereafter, malformations in all species decreased significantly, followed by an abrupt increase in 1996. It was found that in addition to a close correlation between the concentrations of environmental pollutants in the water and in the fish a significant negative correlation existed between surface water temperature and the occurrence of malformed embryos of dab (Limanda limando). These same correlations were also observed for other fish species over time and space. This temperature-related correlation became increasingly visible with decreasing concentrations of organochlorines in fish. From these findings it is concluded that aside from environmental pollutants, natural factors such as temperature may predispose developing fish embryos to the impact of pollutants.