Response of the fish populations of the River Don in South Yorkshire to water quality and habitat improvements.

The River Don in Yorkshire, UK, has suffered a legacy of pollution and land contamination that dates back to the Industrial Revolution. The river continues to be impacted by discharges from industry, mining and sewage sources, resulting in poor water quality and considerable damage to the fish stocks. Some modest reductions in ammonia, biochemical oxygen demand (BOD) and metal levels have been achieved through improvements to sewage treatment works and the shutting down of some industries. The decline in the steel industry has generally led to sustained low and acceptable levels of iron and nickel in the river, although some locations are impacted by ochre from abandoned mines. As a consequence, recreational fishing in the catchment remains restricted at many locations. Fish stocking and enhancement programmes have so far been ineffective due to setbacks from ad hoc pollution incidents and degraded habitats. It is suggested that the water quality and habitat degradation problems be addressed prior to embarking on any large-scale fish stock enhancement programmes. This would require substantial financial investment and it is recommended that funding be actively sought from both internal and external agencies to achieve this objective.