Non-native species invasions threaten the structure, function and biodiversity of ecosystems worldwide, and those of non-native fishes pose amongst the greatest threats to inland waters of the U.K. This PhD investigated the establishment, dispersal and ecological implications of introducing the two non-native fish species, sunbleak Leucaspius delineatus (Heckel, 1843) and topmouth gudgeon Pseudorasbora parva (Temminck and Schlegel, 1842) to inland waters of England. The introduction and initial dispersal of both species can be attributed to the commercial fish trade. Species-specific variability of life history, growth and morphological traits was examined in sunbleak (12 sites) and topmouth gudgeon (3 sites) to assess their role in establishment success. The drift dynamics, i.e. timing and intensity (propagule pressure), of sunbleak and topmouth gudgeon were assessed for source populations to determine dispersal potential. Potential risks for native species posed by these two alien cyprinids were assessed with respect to the parasite fauna and overlaps in resource use. For sunbleak, these were also examined in terms of social integration of this species into a native fish assemblage. Biological resistance to topmouth gudgeon invasion was evaluated by stomach flushing and gut content analysis of native piscivorous fishes. Inter-population variability in life histories and morphological characters were observed in both sunbleak and topmouth gudgeon. Populations of both species matured at small body sizes and between the ages 1 and 2. The fish were of good body condition and exhibited high reproductive investment. In both species, dispersal from source waters followed a diel pattern, with higher rates at night than during the day (e.g. maximum drift densities during May of 2004 and 2005: 9-10 sunbleak per 1000 m -3 at about 23:00 hrs; 40-52 topmouth gudgeon per 1000 m -3 at about 05:00 hrs). Downstream of one source population, microhabitat use of topmouth gudgeon was found to overlap with native species (brown trout Salmo trutta L., European chub Leuciscus cephalus (L.), bullhead Cottus gobio L., stoneloach Barbatula barbatula (L.); both brown trout and chub were observed to prey on topmouth gudgeon. However, predation intensity may be density-dependent and of insufficient level to impede topmouth gudgeon establishment, which was facilitated in the receiving stream by the consistent propagule pressure from on-line source populations. Sunbleak diet and microhabitat use also overlapped with native species (roach Rutilus rutilus (L.) and common bream Abramis brama (L.)) as young larvae, but this decreased with age. Social network analysis of sunbleak-native species interactions revealed that sunbleak creates significantly stronger social bonds with the native species than do natives amongst themselves. No macro-parasites were found in topmouth gudgeon, but two ‘Category II’ non-native parasites Neoergasilus japonicus (Harada, 1930) and Ergasilus briani (Markewitsch, 1932) were found in some populations of sunbleak. The potential for sunbleak to spread beyond their current distribution in England and the species’ social integration behaviour may facilitate the dispersal of these parasites, which may spread faster among communities invaded by sunbleak than in those where this non-native species is absent. The results of this PhD study are discussed within their wider context and their relevance to non-native species risk analysis and management.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:494859 |
| Date | January 2008 |
| Creators | Beyer, Kathleen |
| Contributors | Gozlan, Rodolphe ; Copp, Gordon |
| Publisher | University of Hull |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hydra.hull.ac.uk/resources/hull:1002 |
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