Fish lice could be early indicators for metal pollution in fresh water, say researchers. A Argulus japonicus, a fish louse,, is shown in this image. Water quality in rivers and dams is decaying all over the world, and metal pollution is a major reason. Meanwhile, water resources are very limited. University of Johannesburg scientists Prof Annemariè Avenant-Oldewage and Dr Beric Gilbert published their research in PLoS One.