The aquatic nuisance mussel, Limnoperna fortunei, arrived in Japan before 1987 possibly with the Asian clam imported as food from mainland China. Now the mussel’s distribution has spread to two river systems in central Japan.
Water authorities reported several cases of damage caused by L. fortunei. Most cases of damage were caused by dead mussels clogging small diameter pipes for raw water sampling and monitoring and for cooling water. Clogging of cooling water pipes stopped raw water pumping to a water purification plant and caused the shutdown of a turbine dynamo-electric generator in a hydraulic power plant. The attachment of L. fortunei caused the malfunction of a water level gauge. There was a heavy accumulation of dead L. fortunei in slurry treatment facilities and rotten mussels developed an offensive odour.
Although the screens and pipes of the raw water intake and transmission were inhabited by L. fortunei, problems relating to their decreased hydraulic capacity were not reported. This may have been due to the low reproduction rate and short lifespan of L. fortunei. There was one reproduction period each year, during May to September and their lifespan was two years at most. The growth rate could be about 15 mm yr−1 in shell length. Although chlorine in either free or combined form is effective for the control of L. fortunei larvae, so far water supply authorities have not considered prechlorination in the intake, mainly because prechlorination deactivates the biological nitrification along the pipelines.
Keywords: freshwater mussel, impact, inhabitation, invasion route, Limnoperna fortunei, water supply facilities.