Invasion of the Allegheny River by the spiny water flea (Bythotrephes longimanus)

Abstract

The spiny water flea (Bythotrephes longimanus), has successfully established populations in North American reservoirs and lakes, but little is known of its movement between lake and river systems. Here we document the first longitudinal movement of this aquatic invader in the Allegheny River, Pennsylvania. During spring 2013 we collected samples from the tailrace of Kinzua Dam to the confluence of Oil Creek, Oil City Pennsylvania, a distance of 100 km. The spiny water flea was present along 24 km of the sampled reach, comprising from 10 to 30% of the total zooplankton assemblage. In addition we collected two species of Daphnia, the dominant taxon, and Leptodora kindtii. All three developmental stages of the spiny water flea were present in samples collected (Instars I, II, and III). This study presents one of the first documented expansions of this species from an impoundment to downstream riverine reaches. Its presence warrants further monitoring and appropriate strategies to curb its spread and to investigate its potential impact on the lotic food web.