Studies on the Growth of Common Carp, Cyprinus carpio L., in a Lake Fishery

ABSTRACT Data are presented on the growth of an artificially stocked population of common carp, Cyprinus carpio L. in a South Lancashire rod and line lake fishery. The fish could not be aged from their scales and methods are described for the analysis of directly measured annual growth increments for tagged fish of unknown age in three size classes. Mean growth in weight for carp in the 454–2268 g (1–5 lb) and 2268–4536 g (5–10 lb) size classes was 0.23 and 0.19 kg year −1 ; mean annual length increments were 10.8 and 4.4 mm, respectively. Carp >4536 g were observed to lose weight and length at a mean annual rate of 0.17 kg and 3.7 mm. The implication of these results to the stocking policy for the lake are discussed in conjunction with previously reported data on stock density and catchability. Comparisons between June/July length‐weight regressions for carp at the time of tagging and after 1 and 2 years indicated no significant differences. Causes of growth inhibition by tagging reported by other authors are examined and considered to have been eliminated from the current study in which no adverse influence on growth could be detected. The effects of population density, competition with other species, chemical factors, weed growths and angling pressure on the growth rates of the carp are discussed and their implications to the management of the fishery considered.