Fish community responses to metal pollution

The effect of metal pollution on fish communities was assessed at 47 sites, including a Cd and Zn gradient. Fish community structure was assessed by applying diversity indices, index of biotic integrity and the abundance/biomass comparison method (ABC-index). To relate the community responses to metal pollution, toxic unit values for dissolved metals (TUw) and for metals in fish liver (TUt) were calculated. If all sites were considered only a good relationship was found between the IBI and the TUw, with 56% of the variation in IBI being described. Within the pollution gradient (sites 1-12) the described variation increased up to 85%. Relating the community structure to TUt, the described variation in IBI further increased to 87%. Our results indicate that besides water quality other factors influenced diversity and ABC-index. The IBI proved a suitable index for the assessment of metal pollution, provided that other water quality characteristics meet the water quality criteria.