| 1. |
- Brijs, J., et al.
(författare)
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Remote physiological monitoring provides unique insights on the cardiovascular performance and stress responses of freely swimming rainbow trout in aquaculture
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Investigating the mechanisms that fish employ to maintain homeostasis in their everyday life requires measurements of physiological and behavioural responses in the field. With multivariate bio-loggers, we continuously measured gastrointestinal blood flow (GBF), heart rate, activity and body temperature in rainbow trout (Oncorhynchus mykiss) swimming freely amongst ~5000 conspecifics in a sea cage. Our findings clearly demonstrate that while both acute aquaculture-related stress and spontaneous activity resulted in transient reductions in GBF (i.e. reductions of up to 65%), recovery from stressful handling practices subsequently involved a substantial and prolonged gastrointestinal hyperemia far beyond the level observed prior to the stressor. The gastrointestinal hyperemia may be necessary to repair the damage to the gastrointestinal tract caused by acute stress. Furthermore, heart rate responses to acute stress or voluntary activity differed depending on the individual’s physiological state. Stressed fish (i.e. mean heart rates >70 beats min−1) exhibited a bradycardic response to acute stress or activity, whereas fish with mean heart rates <60 beats min−1 instead demonstrated strong tachycardic responses. Remote monitoring of physiological and behavioural variables using bio-loggers can provide unique insights into ‘real-life’ responses of animals, which can largely differ from the responses observed in confined laboratory settings. © 2019, The Author(s).
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| 2. |
- Brijs, Jeroen, et al.
(författare)
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The final countdown: Continuous physiological welfare evaluation of farmed fish during common aquaculture practices before and during harvest
- 2018
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 495, s. 903-911
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Tidskriftsartikel (refereegranskat)abstract
- Welfare of farmed fish has become of increasing concern for consumers, producers, interest groups and authorities. To improve fish welfare, it is necessary to find indicators that can identify stressful situations early enough so that an intervention can take place before detrimental effects occur. By using heart rate bio-loggers in freely swimming rainbow trout (Oncorhynchus mykiss), combined with plasma cortisol levels and a range of haematological and blood chemistry parameters, we assessed the severity of stress responses induced by a range of common aquaculture practices before and during harvest. Following surgery, transportation and reintroduction with conspecifics in the sea cage, it took similar to 4 days for heart rate to stabilize and for a clear circadian rhythm in heart rate to emerge (i.e. average circadian fluctuation in heart rate of similar to 25 to 27 beats min(-1)). The presence or absence of this circadian rhythm in heart rate could inform researchers in the aquaculture industry whether or not specific farming routines induce unnecessary and prolonged stress. The elevations in heart rate caused by common farming practises such as crowding and transportation (e.g. heart rate increased by similar to 8 and 9 beats min-1 above what would normally be expected for that time of day, respectively) corresponded well with increases in plasma cortisol levels. Stressful farming practises or events (indicated by elevated plasma cortisol levels) such as air exposure during brailing and aquatic hypoxia triggered a hypoxic bradycardia until fish were released back into oxygenated water whereupon heart rate significantly increased to repay the accumulated oxygen debt. Repeated stress induced by multiple farming practises (i.e. combined stressors of crowding, brailing and transportation) clearly had a cumulative and long-lasting effect as heart rate peaked at similar to 25 beats min(-1) above what would normally be expected for that time of day. Heart rate also remained significantly elevated by similar to 9 beats min(-1) the following morning, suggesting that if rainbow trout need to be subjected to multiple stressors during consequtive days, it is recommended that sufficient time for recovery is provided between stressors. This study demonstrates that heart rate monitoring can be useful to assess stress levels of freely swimming fish in sea cages. Moreover, the use of implantable bio-loggers opens up a broad range of possible applications that will allow researchers to investigate the effects of environmental and/or anthropogenic stressors on the welfare of fish under conditions more realistic to the aquaculture industry.
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| 3. |
- Gräns, Albin, 1979, et al.
(författare)
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Post-Surgical Analgesia in Rainbow Trout: Is Reduced Cardioventilatory Activity a Sign of Improved Animal Welfare or the Adverse Effects of an Opioid Drug? : Effects of Post-Operative Analgesia in Fish
- 2014
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:4
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Tidskriftsartikel (refereegranskat)abstract
- The use of fish models in biomedical research is increasing. Since behavioural and physiological consequences of surgical procedures may affect experimental results, these effects should be defined and, if possible, ameliorated. Thus, the use of post-surgical analgesia should be considered after invasive procedures also in fish, but presently, little information exists on the effects of analgesics in fish. This study assessed the effects of an opioid drug, buprenorphine (0.05 mg/kg IM), on resting ventilation and heart rates during 7 days of postsurgical recovery in rainbow trout (Oncorhynchus mykiss) at 10°C by non-invasively recording bioelectric potentials from the fish via electrodes in the water. Baseline ventilation and heart rates were considerably lower compared to previously reported values for rainbow trout at 10°C, possibly due to the non-invasive recording technique. Buprenorphine significantly decreased both ventilation and heart rates further, and the effects were most pronounced at 4–7 days after anaesthesia, surgical procedures and administration of the drug. Somewhat surprisingly, the same effects of buprenorphine were seen in the two control groups that had not been subject to surgery. These results indicate that the reductions in ventilation and heart rates are not caused by an analgesic effect of the drug, but may instead reflect a general sedative effect acting on both behaviour as well as e.g. central control of ventilation in fishes. This resembles what has previously been demonstrated in mammals, although the duration of the drug effect is considerably longer in this ectothermic animal. Thus, before using buprenorphine for postoperative analgesic treatment in fish, these potentially adverse effects need further characterisation.
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| 4. |
- Gräns, Albin, 1979, et al.
(författare)
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Stunning fish with CO2 or electricity: contradictory results on behavioural and physiological stress responses
- 2016
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Ingår i: Animal. - 1751-7311 .- 1751-732X. ; 10:2, s. 294-301
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Tidskriftsartikel (refereegranskat)abstract
- Studies that address fi sh welfare before slaughter have concluded that many of the traditional systems used to stun fi sh including CO 2 narcosis are unacceptable as they cause avoidable stress before death. One system recommended as a better alternative is electrical stunning, however, the welfare aspects of this method are not yet fully understood. To assess welfare in aquaculture both behavioural and physiological measurements have been used, but few studies have examined the relationship between these variables. In an on-site study aversive behaviours and several physiological stress indicators, including plasma levels of cortisol and ions as well as blood physiological variables, were compared in Arctic char ( Salvelinus alpinus ) stunned with CO 2 or electricity. Exposure to water saturated with CO 2 triggered aversive struggling and escape responses for several minutes before immobilization, whereas in fi sh exposed to an electric current immobilization was close to instant. On average, it took 5 min for the fi sh to recover from electrical stunning, whereas fi sh stunned with CO 2 did not recover. Despite this, the electrically stunned fi sh had more than double the plasma levels of cortisol compared with fi sh stunned with CO 2 . This result is surprising considering that the behavioural reactions were much more pronounced following CO 2 exposure. These contradictory results are discussed with regard to animal welfare and stress physiological responses. The present results emphasise the importance of using an integrative and interdisciplinary approach and to include both behavioural and physiological stress indicators in order to make accurate welfare assessments of fish in aquaculture.
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| 5. |
- Hjelmstedt, P., et al.
(författare)
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Continuous physiological welfare evaluation of European whitefish (Coregonus lavaretus) during common aquaculture practices leading up to slaughter
- 2021
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 534
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Tidskriftsartikel (refereegranskat)abstract
- European whitefish (Coregonus lavaretus) is an aquaculture species with the potential for expanded cultivation in the fresh and brackish waters of Northern Europe. Yet, relatively little species-specific information is available regarding the stress responses and associated welfare implications for this species in captivity. We addressed this knowledge gap by using a combination of implantable heart rate bio-loggers and a range of traditional stress indicators (e.g. haematological parameters and plasma concentrations of cortisol, glucose and ions) to comprehensively evaluate the physiological responses of freely swimming whitefish in captivity, as well as when subjected to aquaculture practices and stressors that commonly occur prior to and during slaughter. Whitefish appeared to recover rapidly from surgery, as resting heart rate decreased within 36 h to stabilize at similar to 25 beats min(-1) for the next 18 days when fish were left relatively undisturbed (i.e. personnel were only present when feeding fish). In contrast with previous studies on farmed rainbow trout and Atlantic salmon, whitefish did not exhibit a clear circadian heart rate rhythm, which may be related to species-specific differences in diurnal locomotor activity. Whitefish also appear to have a well-developed capacity for thermal acclimation of heart rate, as daily resting heart rate did not change during the undisturbed period despite an increase in body temperature from similar to 6.8 to 11.2 degrees C. Following acute stressors such as crowding and transportation, the physiological response of whitefish typically involved transient elevations in heart rate, plasma cortisol and glucose, and red blood cell swelling, while plasma [K+] decreased. In contrast, the heart rate of whitefish plummeted following the combination of brailing (i.e. to haul in fish with a brail/net) and CO2 exposure prior to slaughter, while plasma cortisol, glucose and [Ca2+] significantly increased. An unforeseen finding concerns the substantial and long-lasting physiological stress response observed in whitefish when held in close proximity (i.e. within similar to 10 m) to a rainbow trout net pen, as the mean heart rate of whitefish increased from similar to 32 to 43 beats min(-1) (i.e. an increase of similar to 34%). This may represent an innate physiological response to the threat of predation, which consequently increases the allostatic load and energetic expenditure of whitefish when farmed alongside salmonids. To conclude, this study highlights the importance of performing long-term, species-specific evaluations of freely swimming fish in real aquaculture settings, and provides a platform for further research aiming to determine the welfare implications of simultaneously farming predatory and prey species in close proximity.
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| 6. |
- Sandblom, Erik, 1978, et al.
(författare)
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Stress responses in Arctic char (Salvelinus alpinus L.) during hyperoxic carbon dioxide immobilization relevant to aquaculture
- 2013
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 414–415
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Tidskriftsartikel (refereegranskat)abstract
- Physiological responses during immobilization with hyperoxic hypercapnia were determined in cannulated Arctic char (Salvelinus alpinus) exposed for 10 min to mixtures of 10% CO2 in 90% O2 (10:90) or 50% CO2 in 50% O2 (50:50). Results were compared with a previous study on the same group of char using pure CO2 under identical experimental conditions to test the hypothesis that supplemental oxygen may reduce stress and improve welfare during CO2 exposure. While all fish recovered from the two exposures, the time to loss of equilibrium with the 50:50 mixture was significantly shorter than for the 10:90 mixture (143 vs. 276 s); and the time to regain equilibrium was longer (2302 vs. 963 s). Hypertension and bradycardia developed with 10:90, while 50:50 resulted in tachycardia and unchanged blood pressure. Ventilation frequency and amplitude increased significantly with 10:90, whereas ventilation ceased completely with 50:50. Primary and secondary stress responses were evident during recovery in normoxia in both groups as indicated by elevated heart rate and ventilation and increased plasma cortisol. However, recovery appeared to be faster with the 10:90 mixture because ventilation amplitude and plasma cortisol levels declined more rapidly. Nonetheless, the times to loss of equilibrium recorded here with mixtures of oxygen and carbon dioxide bracket that observed previously with pure CO2. Furthermore, the increase in plasma cortisol was similar or higher in the present study suggesting that while supplemental oxygen does not markedly reduce stress or improve welfare during carbon dioxide immobilization, survival and recovery in normoxia are improved.
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| 7. |
- Seth, Henrik, 1979, et al.
(författare)
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Physiological responses and welfare implications of rapid hypothermia and immobilization with high levels of CO2 at two temperatures in Arctic char (Salvelinus alpinus).
- 2013
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 402-403, s. 146-151
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Tidskriftsartikel (refereegranskat)abstract
- Carbon dioxide (CO2) is used for immobilisation of Arctic char (Salvelinus alpinus) prior to slaughter at Swedish aquaculture facilities, and fish are routinely exposed to hypothermia in ice water during transport. Yet, information on stress physiological responses to CO2, temperature extremes and their potential interacting effects is scarce for this cold-water species. Here, blood pressure, heart and ventilation rates and plasma variables including ions, haematocrit, glucose and cortisol were measured in cannulated char during exposure to hypothermia (i.e. a rapid temperature drop from 10 °C to 0.25 °C); as well as to water nearly saturated with CO2 at 10 °C and 0.25 °C to test the hypothesis that hypothermia alleviates stress responses during CO2 exposure. While all fish maintained equilibrium during the 30 min hypothermic challenge, blood pressure, heart and ventilation rates decreased and plasma cortisol increased moderately. CO2 exposure at 10 and 0.25 °C resulted in aversive behavioural reactions before equilibrium was irrecoverably lost after 184 ± 14 and 191 ± 9 s, respectively. The physiological responses to CO2 exposure were largely similar at both temperatures with elevated cortisol levels, reduced heart and ventilation rates and hypotension; although reductions in ventilation amplitude and arterial pulse pressure were significantly more pronounced at 0.25 °C. It is concluded that hypothermia alone is a relatively mild stressor in this species, while CO2 exposure elicits pronounced physiological and behavioural stress responses that are not alleviated by hypothermia.
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| 8. |
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