Spatial variability in the growth of invasive European barbel Barbus barbus in the River Severn basin, revealed using anglers as citizen scientists

Life history trait analyses of non-native fishes help identify how novel populations respond to different habitat typologies. Here, using electric fishing and anglers as citizen scientists, scales were collected from the invasive barbel Barbus barbus population from four reaches of the River Severn and Teme, western England. Angler samples were biased towards larger fish, with the smallest fish captured being 410 mm, whereas electric fishing sampled fish down to 60 mm. Scale ageing revealed fish present to over 20 years old in both rivers. Juvenile growth rates were similar across all reaches. Lengths at the last annulus and Linfinity of the von Bertalanffy growth model revealed, however, that fish grew to significantly larger body sizes in a relatively deep and highly impounded reach of the River Severn. Anglers thus supplemented the scale collection and although samples remained limited in number, they provided considerable insights into the spatial demographics of this invasive B. barbus population.