Analysis of angling vulnerability of common carp, Cyprinus carp/0 L., in catch-and-release angling in ponds

Abstract. The vulnerability of common carp to angling was studied in a drainable pond of 0–4 ha, stocked near the carrying capacity (700 kg/ha) with known numbers of individually marked carp. The numbers of carp hooked and landed ('caught') by each angler were registered during a period of one month. Landed carp were checked for marks. All carp were returned to the pond. The catch results were analysed with use of a simulation model of a pond fishery. The observed catch and recapture frequencies were compared with the expected values. It was shown that the vulnerability of carp to hooking decreased after one experience with a fish hook. Differences in decreased vulnerability to hooking were found within the carp population. This resulted in unequal recapture sequences for the various groups in the population. Analysis of the growth of carp and the capture data indicated that under the experimental conditions of high stocking density, carp that were more vulnerable to angling showed better growth than carp that avoided the hook after a hook experience. The experiments showed that the decreased vulnerability to the fish hook disappeared when the population was not angled for about one year. The carp acquired the hook avoidance behaviour again after one experience with a hook.