Abstract
This study investigated the reproduction of non-native fish species, inferred from the presence of 0+ fish, in three English lowland rivers over an 8 year period. Evidence of self-sustaining populations was found for three non-native fish species, namely zander Sander lucioperca (in the River Trent and Warwickshire Avon), bitterling Rhodeus amarus (in the Trent) and carp Cyprinus carpio (in the Trent and Avon). Notwithstanding, such fishes are currently rare, accounting for <1% of the 0+ fish communities of these two rivers, and no non-native species were recorded from the Yorkshire Ouse. It is possible, however, that improvements in water quality and habitat, together with the potential effects of climate change, may facilitate consolidation and expansion of their populations, as well as those of other non-native fish species already present or introduced in the future. This could have repercussions for the ecology and management of non-native fishes in the UK.
Highlights
Non-native fish species are being reported from an increasing number of waterbodies across the UK (Copp et al 2006)
The 0+ fish populations of the lower River Trent, Warwickshire Avon and Yorkshire Ouse were surveyed at 37 sites (Figure 1, Annex 1) approximately fortnightly/monthly from May 1999 to March 2007 inclusive in daylight hours, using a micromesh seine net (25 m long by 3 m deep, 3 mm hexagonal mesh)
Evidence of self-sustaining populations was found for three non-native fish species, namely zander, bitterling Rhodeus amarus (Bloch) and carp (Annex 2)
Summary
Non-native fish species are being reported from an increasing number of waterbodies across the UK (Copp et al 2006). Not all introductions culminate in self-sustaining populations, with a number of the records of non-native fish species representing captures of either escapees from the ornamental trade or individuals released for angling In common with the majority of rivers discharging into either the English Channel or the southern North Sea, the Trent and Ouse have a high natural diversity of fish species compared with elsewhere in the UK, attributable to the process of colonisation by fishes following the last Ice Age (Wheeler 1977). The Avon is a major tributary of the River Severn, which discharges into the Bristol Channel, and has a less diverse natural fish fauna. The possible implications of establishment of self-sustaining populations of non-native fish species are discussed
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