Removal of pikeperch (Stizostedion lucioperca) from a British Canal as a management technique to reduce impact on prey fish populations

Abstract

Pikeperch (Stizostedion lucioperca) are not indigenous to the UK (Wheeler & Maitland 1973), but following introduction to Eastern England they have now become established in a wide range of stillwaters, rivers and canals across lowland England (Fig. 1). Pikeperch are highly valued sport fish in mainland Europe (Willemson 1983), but not in British waters where the majority of anglers prefer to catch other fish such as the cyprinids, carp (Cyprinus carpio), roach (Rutilus rutilus) or bream (Abramis brama). Associated with the introduction of pikeperch into some waterbodies has been a simultaneous reduction in the numbers of these cyprinids. Since pikeperch were new to the UK and obviously piscivorous, many anglers and some fishery managers attributed such declines in the cyprinid populations to colonisation by the new predator. Subsequently, the managers of British waters colonised by pikeperch have often tried to reduce pikeperch biomass by removal programmes (the process hereafter referred to as culling) in the hope that this would maintain or restore the abundance of prey fish. Pikeperch culls have been promoted for the management of many colonised waters. However, the lack of long-term data on the outcome of these programmes has prevented the evaluation of their effectiveness. Pikeperch were first found in a section of the North Oxford Canal (part of the East Midlands Canal network) in 1976 (Hickley 1986) (Fig. 1). Since 1977, this pikeperch population has been culled annually by the Severn Trent Water Authority (later the National Rivers Authority, Severn Trent Region) (Hickley 1986). During the late 1980s anglers alleged that the fish biomass in the North Oxford Canal had decreased as a consequence of the inRemoval of pikeperch (Stizostedion lucioperca) from a British Canal as a management technique to reduce impact on prey fish populations