A study of the population ecology of the alien cyprinid Pseudorasbora parva (commonly known as the Topmouth gudgeon, but more familiar to aquarists as the Clicker barb) in the UK has confirmed it to be a highly invasive species.
The study by Robert Britton, Gareth Davies, Matt Brazier and Adrian Pinder, to be published in the journal Aquatic Conservation: Marine and Freshwater Ecosystems documents the establishment, population structure and reproduction of the Clicker barb in an infested lake in the Lake District (the name of the lake was withheld for confidentiality) as a case study to show the threat this species poses as an invasive.
The Clicker barb, a species native to eastern Asia, is a highly invasive species in Europe following initial introduction in 1960.
This species was first reported in the UK in 1996; although only four infested sites were reported in 2002, the species has now spread to at least 25 sites.
The Clicker barb has been shown to be a vector of a rosette agent lethal to native cyprinids, and has been classed as an international pest.
The authors sampled the study area (to which the Clicker barb had been introduced in 2000) in 2003, 2004 and 2005 using nets and electricity, then measured the various population parameters of the fish captured.
They found that the Clicker barb had so rapidly established a breeding population that by 2003, it was the dominant species in size classes less than 70 mm and that in the following year, it was the only species in the lake that produced young-of-the-year.
The success of the clicker barb is largely due to its reproductive tactics of early maturity, multiple spawning, male dominance and nest guarding, 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.
It should also be noted that an eradication programme for the Clicker barb was successfully carried out at the study site by the authors in 2006.
The authors conclude ...In combination with the increasing distribution of P. parva and their presence in lakes that provide significant opportunities for fluvial dispersal....it implies that other fish communities in the UK of similar habitat and community structure are threatened by their introduction.
"If the native fish communities of the UK are to be protected from the invasion of this species, then preventative actions should include prohibiting P. parva introduction into new waters and their dispersal from invaded waters.
"Their elimination from infested waters that threaten to provide a pathway for fluvial dispersal will also minimize distribution, and options for this include eradication programmes similar to that completed on this lake, as this appears to have been successful...Otherwise, P. parva will become an alien species that will have to be accepted as a permanent addition to the fish fauna of the UK.
For more information, see the paper: Britton, JR, GD Davies, M Brazier and AC Pinder (2007) A case study on the population ecology of a topmouth gudgeon (Pseudorasbora parva) population in the UK and the implications for native fish communities. Aquatic Conservation: Marine and Freshwater Ecosystems. DOI: 10.1002/aqc.809