Carp feeding activity and habitat utilisation in relation to supplementary feeding in a semi-intensive aquaculture pond

Abstract

A combination of radio telemetry and electrofishing was used to assess seasonal feeding activity and habitat utilisation of common carp (Cyprinus carpio) in a large (130 ha) semi-intensive aquaculture pond receiving supplementary feed. While telemetry indicated no difference in fish habitat utilisation by size, age or sample year, all fish showed a strong preference for the supplementary feed area (SFA) during the feeding period, electrofishing indicating a 15× higher fish concentration. Despite this, not all of the feed provided was eaten immediately. Carp activity was more evenly spread over the pond in summer/autumn and more concentrated at the SFA in spring. There was a significant shift to deeper waters in winter. Diet analysis indicated a high preponderance of cereal in SFA fish, with natural food (mainly zooplankton) dominant at natural feeding areas. The proportion of ‘emergency’ food (e.g. detritus) was similar in both areas, as was the index of gut fullness. Our results confirm that concentrated and repeated supplementary feeding in one area results in aggregation of carp, potentially leading to uneven population growth and flesh quality and reduced water quality from turbidity and increased nutrient input. As an alternative, we suggest spreading less supplemental feed over a greater area at wider time intervals. This would ensure (a) full utilisation of feed, reducing costs and increasing water quality, and (b) more homogenous fish distribution, ensuring more efficient use of natural food, reduced turbidity, more homogenous size/weight distribution and improved product quality.