Biometric Data and Bone Identification of Topmouth Gudgeon Pseudorasbora Parva and Sunbleak Leucaspius Delineatus

Identification and analysis of the size and composition of prey taken by piscivorous predators assists in the further understanding of ecology of piscivorous fauna (Mann & Beaumont 1980, Hansel et al. 1988, Copp & Roche 2003). Comprehensive evaluation of the digested prey is central to the assessment of predation impacts and is equally important for sustainable fisheries management. Two non-native fish species in England that may be potential prey for native species are sunbleak Leucaspius delineatus (Heckel) and topmouth gudgeon Pseudorasbora parva (Temminck et Schlegel). These species were introduced to English waters in the mid 1980’s (Farr - Cox 1996, Gozlan et al. 2002) where they have since developed extensive populations (Gozlan et al. 2003, Hickley & Chare 2004). Recent studies associate sunbleak and topmouth gudgeon with novel non-native parasites (Beyer et al. 2005, Gozlan et al. 2005). Results such as these have emphasized the need to be able to identify these two species as part of the native predators’ diet. The aim of the study was to provide a tool for species identification and to elaborate the biometric relationships between bone dimensions and body size of sunbleak and topmouth gudgeon. Head bones of fish are particularly useful for identifying the size and composition of prey species from the food remains of predators, as they withstand digestion and are taxonomically valuable (Copp & Kováč 2003)