Fish welfare research programme: Effects of retention of fish in keepnets

Capture by angling, and subsequent confinement within keepnets, exposes fish to several adverse factors. These primarily comprise the potential for physical damage arising from capture and handling, exposure to potentially harmful changes in water quality within the keepnets, and physiological stress resulting from the combination of stimuli experienced by the fish during and subsequent to capture. Concern within the angling and fisheries management community regarding the welfare of fish populations subject to angling pressure has led to research on this subject. The question of water quality within keepnets during the confinement of fish has been addressed in a previous study by the Institute of Freshwater Ecology, commissioned by the National Federation of Anglers (Pottinger, 1992). This study established that statistically significant changes in water quality do occur during the confinement of fish within keepnets but that the magnitude of these changes does not represent a threat to the well-being of the fish. The aim of the present study was to address a second area of concern related to angling practices; that of physiological stress associated with the capture, handling, and confinement of fish within keepnets. The findings of the study suggest that the retention of carp in keepnets following capture may not represent an additional source of stress, over and above that of capture, and may not affect the rate of recovery of the fish from the initial capture stress. Capture and confinement of fish for periods of up to four hours appears to constitute an acute, rather than chronic, stress and as such is unlikely to have an adverse long-term effect on the well-being of the fish. This conclusion is based on the physiological changes observed in the fish, and does not take into account the possible additional effects of physical damage incurred during capture, unhooking and confinement.