Differences in seasonal abundance patterns of golden mussel larva between dam reservoirs connected by headrace channel

Golden mussel Limnoperna fortunei is a freshwater bivalve that adheres to hard substrate and underwater structures, resulting in major biofouling problems. We investigated population dynamics of larva of L. fortunei in two dam reservoirs, Lake Ohshio and Lake Takenuma, which are connected by a headrace channel. The larval density in Lake Ohshio was more than 1,000 ind./m³ with maximum of 80,000 ind./m³ in summer of 2007 and 2008. The density in Lake Takenuma was much lower and maximum value was near around 200 ind./m³. Water temperature (WT) and dissolved oxygen concentration (DO) were almost uniform regardless of water depth in Lake Ohshio because of destratification due to continuous aeration. Summer WT and DO in the lake were considered to be kept good for the survival and reproduction of L. fortunei. On the other hand, summer stratification was found for WT and DO in Lake Takenuma as common deep reservoirs. Low WT and DO in summer found in deep stratum of the lake are not considered to be acceptable for the survival of this species. Results of this study suggest that the aeration for water quality conservation could induce the heavy infestations of L fortunei in Lake Ohshio.