Abstract

Mature noble crayfish were studied in different areas in a lagoon downstream from a steel rolling mill to find possible correlations between environmental pollution and the physiological condition and edibility of the crayfish. In the most contaminated sections of the lagoon temperatures were elevated and there were higher levels of metals, especially iron, zinc, copper and lead in the sediment. The waste waters contain elevated concentrations of iron, zinc and copper and detectable concentrations of mineral oils. In combined samples, male crayfish from the more contaminated area had higher dry matter content and total energy in the hepatopancreas but lower relative hepatopancreas weight than in combined samples from cooler sections. Molting and reproduction were disturbed in the most contaminated part. Iron and copper concentrations in crayfish hepatopancreas were higher in the contaminated sections than elsewhere in the lagoon while zinc concentration was relatively constant all over the lagoon. Copper, iron, and zinc were consistently higher in the hepatopancreas of males than females, both in the study site and reference sites. The lead concentration in crayfish hepatopancreas was usually <0.2 µg g^-1 (d.w.). The cadmium concentrations in the hepatopancreas of mature females from all parts of the lagoon and in males in more contaminated sections were over 0.3 mg kg^-1, fresh weight. Dioxin and PCB concentrations in the hepatopancreas of large male crayfish were within acceptable limits. The crayfish in the lagoon were darker in appearance than reference crayfish but taste and smell were similar. Due to Finnish legislation, those crayfish from the lagoon could not be sold. However, household use of the crayfish, based on heavy metal and hydrocarbon concentrations, could be permitted if the hepatopancreas was not eaten.

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