QUANTITATIVE ASSESSMENT OF MELANOMACROPHAGE CENTERS (MMCS) IN DAB LIMANDA-LIMANDA ALONG A POLLUTION TRANSECT IN THE GERMAN BIGHT

This study attempted to demonstrate whether an aspect of non-specific cellular immunity could be used as an indicator of fish health in populations of dab Limanda limanda exposed along a pollution gradient. Replicate samples of dab spleens were obtained during the Bremerhaven Workshop from a series of stations along a transect in the German Bight. Histochemical techniques, to demonstrate the components of the pigmented materials within melanomacrophage centres (MMCs), indicated varying amounts of breakdown cellular products (notably haemosiderin) to be present. The haemosiderin component was measured in each spleen section with the aid of a computerized image analyzer. Comparative results showed some inconsistencies in amounts of haemosiderin within MMCs between individual fish and replicated samples on stations. However, there were significant differences (p < 0.05) between stations overall, the amounts of haemosiderin being least at Stns 3 & 9. Although these results may indicate an effect of contaminants, no apparent correlation with disease prevalences in the dab population sampled could be established. The technique seems promising, but some problems are mentioned and discussed.