Abstract
In this study, we look closer at how high fish densities influence wound repair mechanisms in post-smolt Atlantic salmon. The fish were wounded with a 5 mm skin punch biopsy needle and stocked at two different densities, a high fish density (100 kg/m3) treatment and a low fish density treatment (20 kg/m3) serving as the control. The healing wounds were followed for 57 days with samples taken 1, 3, 7, 14, 36, 43 and 57 days post wounding. The transcriptomic analysis suggests that high fish density enhance inflammation and represses cell proliferation, tissue secretion and collagen synthesis in the healing wounds. The histological analysis further showed delayed epidermal and dermal repair in the high fish density treatment compared to control. The overall wound contraction was also altered by the treatment. In conclusion, high fish density enhances immune responses and delay tissue repair, which ultimately results in delayed wound healing.
Highlights
Sustainable growth in the Atlantic salmon (Salmo salar) aquaculture sector depends on good fish health and welfare
Dietary intake of zinc enhanced epidermal repair in Atlantic salmon[16], while the dermal repair was promoted in Rainbow trout (Oncorhynchus mykiss) with high dietary levels of vitamin C17
Basal levels of plasma cortisol in unstressed salmonid fish are normally in the range 0–5 ng/mL, while crowding resulted in an elevation of plasma cortisol to 10 mg/mL21. These results suggest that cortisol as a sole indicator of animal performance during long-term intensive rearing conditions may be misleading and other parameters should be included in order to assess animal welfare
Summary
Sustainable growth in the Atlantic salmon (Salmo salar) aquaculture sector depends on good fish health and welfare. In Atlantic salmon, low water temperature result in delayed epidermal repair[11,16], while the stress hormone cortisol delay the dermal repair processes[12]. Dietary intake of zinc enhanced epidermal repair in Atlantic salmon[16], while the dermal repair was promoted in Rainbow trout (Oncorhynchus mykiss) with high dietary levels of vitamin C17. Other factors such as therapeutics and immunostimulants may affect the wound healing rate in fish[18,19,20]. The present study was designed to test the hypothesis that high fish density delays wound repair in post-smolt Atlantic salmon.
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