Grote, Johanna2024-08-232024-08-232024-08-23https://hdl.handle.net/2077/83093Oxygenation of the cardiac muscle tissue is essential for survival in both fish and mammals. Unlike mammals, most fish rely on oxygen-poor luminal venous blood flowing through the spongy myocardium to oxygenate the cardiac tissue. However, athletic salmonids such as rainbow trout (Oncorynchus mykiss) possess an additional layer of myocardial cells outside of the spongy myocardium known as the compact myocardium. This layer is associated with increased cardiac muscle mass and volume, but it also distances individual cells from the luminal oxygen supply. Consequently, the compact myocardium depends on the development of a coronary circulation to supply the cardiac cells with oxygen-rich blood. This supply is essential for maintaining cardiac function. Notably, farmed salmonid fish exhibit deviations in heart morphology compared to their wild counterparts, making them susceptible to decreased cardiac performance and cardiac diseases. In this study, microscopic and macroscopic traits of hearts in farmed rainbow trout were investigated. The results are discussed in relation to cardiac performance and farming conditions. Consistent with other studies, a high prevalence of rounded ventricles and misaligned bulbus arteriosus was observed in our samples. Furthermore, this project identified cases of excess collagen distribution within the compact myocardium, which suggest an old injury caused by myocardial ischemia, presence of coronary anatomy anomaly, and ventricular hypoplasia. These findings underscore the variability of cardiac abnormalities found in farmed salmonid fish compared to their wild counterparts and contributes further to the discussions about cardiac health in farmed fish from a fish welfare and economic perspective.engText