Aquaculture Europe 2023

September 18 - 21, 2023


Add To Calendar 19/09/2023 14:45:0019/09/2023 15:00:00Europe/ViennaAquaculture Europe 2023CORONARY LESIONS IN SALMONID FISH – IMPACT ON ENVIRONMENTAL AND AQUACULTURE STRESS TOLERANCEStrauss 3The European Aquaculture Societywebmaster@aquaeas.orgfalseDD/MM/YYYYaaVZHLXMfzTRLzDrHmAi181982


Erik Sandblom*1 Daniel Morgenroth2, Lucas Zena1, Heidi Mortensen1,5 , Nicklas Wallbom1 , Tristan McArley1, Michael Axelsson1 , Jeroen Brijs3,  Ida Beitnes Johansen4, Albin Gräns2 and Andreas Ekström1.


1Dept of Biological and Environmental Sciences, University of Gothenburg, Sweden

2Dept of A nimal E nvironment and Health, Swedish University of Agricultural Sciences, Sweden

3Dept of Zoology, University of Innsbruck, Austria

4Dep t of Preclinical Sciences and Pathology , Norwegian University of Life Sciences, Norway

5Fiskaaling , Aquaculture Research Station of the Faroes, Faroe Islands


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S ome fishes including salmonids have a coronary circulation that supplies the outer compact myocardium of the heart with fully oxygenated blood. This arterial blood supply complements the luminal venous O2 supply that delivers relatively poorly oxygenated blood to the inner spongy myocardium. T he role of the coronary circulation may be of particular relevance in farmed salmonid fishes , as our group (and others) have shown that they  more  frequently develop  lesions  and arteriosclerosis in the main coronary artery ;  a condition that  narrows the vessel lumen and  may  decrease blood flow to the myocardium  (Brijs et al, 2020; Farrell, 2002). This condition can , in turn, reduce overall cardiac  and metabolic performance, and possibly  the tolerance to environmental stressors that incur an elevated metabolic challenge . There is also a growing body of  evidence  demonstrating that coronary lesion development is positively correlated with factors promoting rapid growth in the smolt production phase (e.g., supra-optimal rearing temperatures ; Brijs et al, 2020), and  may be a  key factor underlying adult fish mortality in aquaculture (Poppe et al , 2021) . Yet, it is still not fully understood how coronary blood flow affects overall cardiorespiratory performance. Moreover, its functional role in setting tolerance limits to environmental extremes such as heat waves and hypoxia, and how it affects resilience to stressful metabolic challenges in aquaculture, has not been extensively studied . Thus, to analyze the functional significance of coronary oxygen delivery in salmonids , we measured in vivo  coronary blood flow under various thermal regime s in male and female rainbow trout (Ekström et al, 2017) . In an additional series of experiments, we surgically ligated the coronary artery  to mimic  extreme coronary arteriosclerosis and explored  its impact on cardiovascular performance and metabolic scope (Ekström et al, 2017; Morgenroth et al, 2021), a s well as  hypoxia and warming tolerance limits  (Ekström et al ,  2019;  Morgenroth et al, 2021).

Material and methods

F ish were anesthetized in  aerated freshwater (10°C) containing buffered MS-222. In one experiment, t he coronary artery was dissected free and a Transonic transit time blood flow probe was placed around the vessel. In other experiments , the vessel was exposed and  either ligated with a silk suture or left intact resulting in surgically ligated and sham operated experimental groups, respectively. In some experiments, sham and  ligated  fish were additionally instrumented with a flow probe around the ventral aorta to measure cardiac output or custom-made subcutaneous electrodes to record the electrocardiogram (ECG) and heart rate. Fish were typically left to recover from surgery for 24-48 h in respirometers to record oxygen consumption rate and then exposed to various metabolic and environmental challenges including exhaustive exercise , acute warming and  aquatic hypoxia.

Results and Discussion

Routine coronary blood flow at 10°C was markedly higher in females than males (0.56±0.08 vs. 0.30±0.08 ml min-1 g-1 ventricle). Warming increased coronary  blood  flow in both sexes until 14°C, at which it peaked and plateaued. This meant that the scope for increasing coronary  blood  flow during warming was 101% in males, but only 39% in females. While coronary ligation reduced routine stroke volume relative to  sham operated  trout with intact coronaries, cardiac output and standard metabolic rate was maintained via an increase in heart rate. However, coronary ligated trout had reduced maximum oxygen consumption rate and aerobic scope when subjected to a 5 min  exhaustive exercise protocol , and  they  had a markedly reduced ability to increase stroke volume to maintain cardiac output when bradycardia developed during acute hypoxia exposure. This was associated with a slightly reduced hypoxia tolerance in coronary ligated trout . During acute warming, coronary ligation caused cardiac function to collapse at lower temperatures and significantly reduced the overall  acute warming  tolerance relative to  sham operated  trout with intact coronaries.


Collectively, our findings show that coronary perfusion improves cardiac O2 supply and overall cardiorespiratory function at environmental extremes, which benefits tolerance to environmental and anthropogenic metabolic challenges. The aquaculture industry should, therefore,  consider  the  potentially detrimental effects of rapid smolt growth rate on coronary health and functionality , as this may result in raising fish that are more susceptible to environmental and metabolic stressors in challenging farm environment s. In light of these findings ,  we are currently conducting  several new experiments to  shed light on  how juvenile rearing conditions subsequently  impact  cardiac and coronary health of  the adult fish .