Lepeophtheirus salmonis is an ectoparasite causing economic concerns in Atlantic salmon farming. Salmon lice infestation management methods can be stressful and impact fish welfare. This work investigated the stress effect on the attachment of L. salmonis copepodids to Atlantic salmon through two approaches: (a) handling by netting and air exposure (acute stress), and (b) crowding with restricted surface access in a tank (chronic stress). In the first experiment, we compared the number of attached L. salmonis and cortisol levels between a group of handled salmon and a control group. In the second experiment, a group of densely packed salmon was compared to a control group based on the number of attached copepodids, cortisol levels and neutrophil:lymphocyte ratios. Handled salmon showed significantly higher plasma cortisol levels (p < .001) and more attached copepodids (p = .01) than control salmon. Conversely, the cortisol level and number of attached copepodids were not significantly different between the densely packed and control salmon (p > .05). The neutrophil:lymphocyte ratio was significantly higher (p = .0014) in the densely packed salmon than in the control salmon. Handling salmon increased their risk of infestation by L. salmonis. This has implications for reinfestation rates following delousing treatments in commercial salmon aquaculture, which often involve crowding and handling salmon.

中文翻译：

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处理和拥挤对大西洋鲑（Salmo salar L.）对鲑鱼Leopophtheirus salis（Krøyer）立足点的敏感性的影响

鲑鱼Leopophtheirus是一种外寄生虫，引起大西洋鲑鱼养殖的经济问题。鲑鱼虱子侵扰管理方法可能会产生压力并影响鱼类的福利。这项工作通过两种方法研究了对鲑鱼立足梭菌附着在大西洋鲑鱼上的应力影响：（a）通过网和空气暴露的处理（急性应力），以及（b）在水箱中拥挤受限的表面进入（长期应力） ）。在第一个实验中，我们比较了附着的鲑鱼L.和一组处理的鲑鱼与对照组之间的皮质醇水平。在第二个实验中，根据附着的双足类动物的数量，皮质醇水平和中性粒细胞与淋巴细胞的比例，将一组密集包装的鲑鱼与对照组进行了比较。处理的鲑鱼 比对照鲑鱼显示出显着更高的血浆皮质醇水平（p  <.001）和更多的附着立足菌（p = .01）。相反，在密集包装的鲑鱼和对照鲑鱼之间，皮质醇水平和附着的立足动物的数量没有显着差异（p  > .05）。 在密集包装的鲑鱼中，嗜中性粒细胞：淋巴细胞的比率显着高于对照鲑鱼（p = .0014）。处理鲑鱼会增加其侵染的风险，鲑鱼。这对商业鲑鱼水产养殖中的诱杀处理后的复生率产生了影响，该处理通常涉及鲑鱼的拥挤和处理。