Edinburgh Napier University

  The PhD is to investigate the ecological implications of invasive bullhead in Scotland. Bullhead is a bottom-dwelling freshwater fish that has been officially documented in Scottish waters since the 1960’s. In other areas of introduction bullhead have been found to negatively impact native fish; displacing species, increasing parasite infection rates and preying upon the eggs of native salmonids. These perceived threats, in conjunction with its human-mediated introduction, have led to bullhead’s designation as invasive in Scottish waters. In England, where bullhead in native, the species has undergone taxonomic revision and is now classified as Cottus perifretum. To date, no study has investigated the taxonomic identity of Scottish bullhead. I used morphological and molecular techniques to provide a definitive taxonomic classification of Scottish bullhead. In addition, I examined parasite links between bullhead and native fish and invertebrate species. Results will be used to investigate whether isolated Scottish bullhead populations are genetically similar to native English bullhead, and determine if bullhead are responsible for introducing novel parasites to Scottish freshwater systems.