Coupling insights from a carp (Cyprinus carpio L.) angler survey with feeding experiments to evaluate composition, quality, and phosphorus input of groundbait in coarse fishing

A carp angler survey indicated that specialised carp anglers used on average 215 kg groundbaits (mostly cereals, nuts, beans, boilies) per year which corresponded to a mean annual gross P-input of 1018 g P angler). A feeding experiment was conducted with juvenile carp fed with a random sample of the main bait types used in coarse angling to estimate the nutritional quality and P-retention efficiency. The investigated groundbaits had a rather low nutritional quality. Based on the examined P-retention efficiencies, the net annual P-input was calculated to be 839 g P per angler. To counterbalance this P-input, an annual harvest rate of 175–225 kg carp biomass per angler would be necessary. Thus, under certain conditions, a substantial contribution by carp and other coarse angling to the P-loading is likely. Further studies on the issue of groundbaiting are needed to develop guidelines for more effective management of coarse angling.