title: Changes in the drift and the settlement of the freshwater mussel Limnoperna fortunei along a headrace channel.
abstract: The nuisance species Limnoperna fortunei is a freshwater mussel whose infestations have harmed water intake facilities, such as water supply systems. We investigated the changes in the drift and the settlement of L. fortunei along a headrace channel. The densities of the drift and the settlement both decreased dramatically with the downstream distance from the L. fortunei source (a reservoir). In comparison with larval densities in the reservoir, drift densities decreased by 10 to 25% at 0.5 km downstream from the reservoir, and were less than 2% at sites more than 4.8 km downstream. Although larval densities at midnight (0:00-2:00) were approximately 1.5 times higher than those at noon (12:00-14:00) in a shallow layer (3 m depth) of the reservoir, we found no diurnal variation of drift densities in the headrace channel. Settlement densities at the site nearest the intake gate were much higher than those of the other sites further downstream in the headrace channel. The L. fortunei adult population in the channel could reduce drift individuals by attracting the larva. The attraction probably induces the massive aggregation at the location of the channel immediately below the drift source, resulting in biofouling.
authors.affiliation: Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry, 1646 Abiko, Chiba 270-1194, Japan. d-nakano@criepi.denken.or.jp
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nakano
authors.forename: Takuya
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Isamu
authors.initials: I
authors.lastname: Sakaguchi
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000502:physiology*; D017753:Ecosystem; D005618:Fresh Water; D058865:Introduced Species; D007564:Japan; D011156:Population Density; D013997:Time Factors; D014872:Water Movements