The epidermal mucus protects fish against harmful environmental factors and the loss of physiological metabolites and water. It is an efficient barrier between the fish and the biosphere. The integrity of the skin mucus is thus of vital importance for the welfare and survival of the fish. Since excreted proteins and small molecules in the mucus can mirror the health status of the fish, it is a valuable matrix for monitoring stress, pathogen exposure, and nutritional effects. Several methods for sampling epidermal mucus from different fish species have previously been described, but information about their efficiency or the comparability of mucus analyses is lacking. In the present study, skin mucus from farmed Atlantic salmon was therefore sampled by three methods, including absorption with tissue, wiping, and scraping with a blunt blade, and the mucus proteome was analyzed by ultra-high pressure liquid chromatograph high-resolution mass spectrometry. The measured protein content, numbers, compositions and the observed data quality were compared between sampling methods. Furthermore, functional annotation and classification of the identified proteins was performed. The results showed that the three skin mucus sample types differed qualitatively as well as quantitatively. The absorbed mucus was the least tainted by proteins resulting from damage inflicted to the fish epidermis by the sampling procedure. Wiped mucus showed a better protein yield than absorbed and delivered a larger proteome of identifiable proteins, with less contamination from epithelial proteins than observed for scraped mucus. We recommend that future research of mucus should use the absorption method in cases, where it is important that the mucus is devoid of proteins from the underlying epithelium, and the wiping method, when protein yield is crucial or when the proteome of the outer epithelium is of interest.

表皮粘液可保护鱼类免受有害环境因素以及生理代谢物和水的流失。它是鱼类与生物圈之间的有效屏障。因此，皮肤粘液的完整性对于鱼类的福利和生存至关重要。由于粘液中排出的蛋白质和小分子可以反映鱼的健康状况，因此它是监测压力，病原体暴露和营养影响的宝贵基质。先前已经描述了几种从不同鱼类中采样表皮粘液的方法，但是缺乏有关其效率或粘液分析可比性的信息。因此，在本研究中，通过三种方法对养殖的大西洋鲑鱼的皮肤粘液进行了采样，包括用组织吸收，擦拭和用钝刀片刮擦，通过超高压液相色谱-高分辨率质谱法对粘液蛋白质组进行了分析。在采样方法之间比较了测得的蛋白质含量，数量，组成和观察到的数据质量。此外，对所鉴定的蛋白质进行功能注释和分类。结果表明，三种皮肤黏液样本类型在质量和数量上都存在差异。采样程序对鱼表皮造成的损害所吸收的蛋白质对蛋白质的污染最小。擦去的粘液比吸收的粘液显示出更好的蛋白质产量，并提供了更大的可识别蛋白质蛋白质组，与刮擦的粘液相比，上皮蛋白的污染更少。我们建议将来对粘液的研究在某些情况下应使用吸收方法，