Cardiovascular, ventilatory and total activity responses of brown trout to handling stress

Abstract

Changes in total activity, heart and ventilation rates were observed in 2‐year‐old brown trout, following handling stress, using non‐contact bioelectronic monitoring equipment. Experiments were carried out in laboratory conditions at water temperatures below 4° C, Transfer between tanks as well as 5 min restraint stress increased the total activity of fish for 24 to 48 h, after which it declined to near the pre‐stress level. The transfer and struggle both elevated the heart rate for 3 to 4 days. Ventilation rate was elevated to a maximum of about 30% above the nominal level and recovered within 3 to 4 days. Both heart and ventilation rates were higher in feeding fish relative to fasting fish after stress and rates remained higher throughout a 7 day period of recovery. A diel rhythm of lower rates during the night appeared in both heart and ventilation rates within 3 to 4 days after handling stress.

Do fishes have nociceptors? Evidence for the evolution of a vertebrate sensory system

“…In our behavioural experiments, we trained fishes to come to a feeding ring in response to a light cue and then assigned them to one of four treatment groups; three of these groups had bee venom, acetic acid or saline injected into the lips and the fourth group was simply a handled control. After injection of algogenic substances, the resulting increase in opercular rate is similar to that recorded when trout are swimming at maximum speed (Altimiras & Larsen 2000) and the rate is much greater than the rate recorded after handling stress (increase to a maximum of 69 beats min 21 ; Laitinen & Valtonen 1994). The control and saline groups showed similar increases in opercular beat rate to stressed fishes (Laitinen & Valtonen 1994) and this is probably the result of the handling and anaesthetic procedure.…”

“…After injection of algogenic substances, the resulting increase in opercular rate is similar to that recorded when trout are swimming at maximum speed (Altimiras & Larsen 2000) and the rate is much greater than the rate recorded after handling stress (increase to a maximum of 69 beats min 21 ; Laitinen & Valtonen 1994). The control and saline groups showed similar increases in opercular beat rate to stressed fishes (Laitinen & Valtonen 1994) and this is probably the result of the handling and anaesthetic procedure. Respiratory changes have been demonstrated in mammals and humans enduring a nociceptive event (Kato et al 2001) and so this dramatic rise in ventilation rate may be a physiological response to noxious stimulation in the rainbow trout.…”

“…This may be similar to guarding behaviour, where an animal avoids using a painful limb to prevent more pain and damage being caused to the affected area (Gentle 1992). Handling and anaesthesia are known to be stressful, causing an elevation in respiration rate (Laitinen & Valtonen 1994), and would account for the delay in the saline and control groups performing the conditioning task. Giving the noxiously stimulated trout softer food did not affect the time taken to begin feeding again.…”

Animal welfare perspectives on recreational angling

“…Respiration rate, measured as opercular beat rate, almost doubled in noxiously stimulated individuals (52-98 beats/min) whereas controls showed a typical stress induced increase to only 68 beats/min. These high respiration rates in the noxious group are similar to rates recorded when the rainbow trout is at its maximum sustained swimming speed and so these injected fish are ventilating at a high rate indicating the dramatic effect of noxious stimulation (Laitinen and Valtonen, 1994). Increased respiration rates are also exhibited by higher vertebrates when they experience a painful event (Kato et al, 2001).…”

Estimating oxygen uptake rate from ventilation frequency in the reef fish Sparisoma viride

“…This is probably why ventilation frequency has hardly been used to estimate metabolic activity but has mainly been used as a n indicator of stress (e.g. Cairns & Garton 1982, McCloskey & Oris 1991, Szyper & Lutnesky 1991, Baldwin et al 1994, Laitinen & Valtonen 1994, Zimmerman & Watters 1994). Oswald (1978) recorded electromyograms from red fibres in a muscle involved in closing the mouth, and found relatively low (near resting level) and constant ventilation rates (maximum increase 52 to 56 % over lowest rate) for brown trout in their natural habitat.…”