Spatial variation in the somatic growth rates of E uropean barbel B arbus barbus : a UK perspective

The E uropean barbel B arbus barbus is threatened in areas of its range because of its sensitivity to anthropogenic disturbance in riverine habitats and, in the UK , is indigenous to a relatively small number of east‐flowing rivers, with nonindigenous populations present in other rivers following introductions for angling enhancement. Fish stock assessment surveys completed between 2002 and 2010 collated age and growth data from 20 rivers across their indigenous and nonindigenous UK range. Analyses revealed that individuals present in samples are of 21 years old, with growth rates highly variable between rivers. There was no relationship between growth rates and the maximum age of fish per river, and there was no difference in growth rates between their indigenous and nonindigenous ranges. A range of abiotic data were collated and analysed against the growth data; these analyses suggested higher mean growth rates were evident in rivers of higher biological water quality (expressed as B ritish M onitoring W orking P arty S core) and higher mean air temperatures (used as a surrogate of water temperature). That growth of B .  barbus was significantly and positively enhanced by increased biological water quality was in contrast to cyprinid fishes such as roach R utilus rutilus and suggests that as river water quality continues to improve through reduced nutrient inputs, further ecological changes are likely in riverine fish communities.