Pseudorasbora parva

Regarded as pest which competes with the fry of other species due to its high reproductive rate. (Welcomme 1988).

out-competing other fishes for food resources and preying on the eggs and larvae of other species (Stein & Herl 1986; Xie, Cui & Li 2001), (Pinder et al., 2005)

P. parva has been classified as an international pest species (Welcomme 1992). Until recently, the hypothesised risks that this Asiatic invader poses to European freshwater biodiversity, such as out-competing other fishes for food resources and preying on the eggs and larvae of other species (Stein & Herl 1986; Xie, Cui & Li 2001), have remained unquantified (Pinder 2005). However, the recent discovery that P. parva is a healthy host to an emergent infectious disease (Rosette-like Agent, closely related to Sphaerothecum destruens), which threatens European fish diversity (Gozlan et al. 2005), is the first real evidence that P. parva is capable of causing real ecological damage to freshwater ecosystems outside its native range. (Pinder et al., 2005)

To demonstrate the threat of P. parva to fisheries in the UK, a case study is presented on a lake located in the Lake District of England where the species was introduced in 2000. The species rapidly established a breeding population that, by 2003, was the dominant species in size classes 570 mm. In 2004, they were the only species in the lake that produced young-of-the-year. P. parva adopted the reproductive tactics of early maturity, multiple spawning, male dominance and male nest guarding; sexual dimorphism was manifested in larger body size of males. These traits were in contrast to the resident, native species of the lake, including roach Rutilus rutilus and gudgeon Gobio gobio, which adopted traits of later maturity and single spawning. This case study, therefore, revealed relatively rapid establishment of a P. parva population, their subsequent numerical dominance of the fish community, and the impediment of the recruitment of native fish. (Britton et al., 2006)