Abstract
Brook trout (Salvelinus fontinalis) is a species of fish native to North-East America. Brook trout are also commercially raised in large numbers for food production. Skin infection and/or parasite outbreaks can have a serious economics effect on aquaculture businesses. For this reason, it has been hybridized with the more resistant Arctic char (Salvelinus alpinus). The aim of this study was an examination of the epidermal structure and dynamic in brook trout and its Arctic char hybrid which is less sensitive to skin infection. The samples of fish (72 brook trout, 72 brook trout × Arctic char hybrid) from fish farm in Pravíkov (49°19’10”N, 15°5’40”E) were collected five times during the year 2011. Absolute and relative epidermal thickness (in relation to body size) and relative proportion of secretory cells in a given volume of epidermis were measured. The epidermis structure of brook trout and brook trout × Arctic char hybrid both display similar seasonal dynamics, with a decrease in absolute and relative epidermal thickness and a reduction in the relative percentage of mucous secretory cells over the summer. On the other hand, the lower absolute (mean 103 µm (range 84–146 µm) in brook trout; 88 µm (range 68–115 µm) in hybrids) and relative epidermal thickness (mean 4.8 (range 3.6–6.8) in brook trout; 4.4 (range 2.9–6.4) in hybrids) and lower volume of secretory cells was observed to the hybrid (mean 28% (range 19–33%) in brook trout; 23% (range 10–30%) in hybrids). It can interrelate with their higher resistance to infection and/or parasite outbreaks.
Highlights
The only char species native to Europe is the Arctic char (Salvelinus alpinus), which is found across northern Europe and in the Alpine and Pyrenean mountain ranges (Kottelat and Freyhof 2007)
The aim of this study was an examination of the epidermal structure and dynamic in brook trout and its Arctic char hybrid which is less sensitive to skin infection
We examined the skin structure of brook trout and brook trout × Arctic char hybrids, and discussed the findings in the light of char biology and aquacultural practice
Summary
The only char species native to Europe is the Arctic char (Salvelinus alpinus), which is found across northern Europe and in the Alpine and Pyrenean mountain ranges (Kottelat and Freyhof 2007). High fish densities increase the risk of mechanical injury, meaning that char become highly susceptible to Monogenea infection and, especially, furunculosis Aeromonas salmonicida (Egidius 1987; Cipriano and Bullock 2001; Haffray et al 2009). Such infection and/ or parasite outbreaks can have a serious economic effect on aquacultural businesses. This has prompted fish farmers to research means of reducing the risk of infection, including selection and hybridisation One such attempt has been the induced hybridisation of brook and Arctic char. We examined the skin structure of brook trout and brook trout × Arctic char hybrids, and discussed the findings in the light of char biology and aquacultural practice
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