Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR, USA.
Department of Microbiology, Oregon State University, Corvallis, OR, USA.
J Fish Dis. 2021 Sep;44(9):1423-1434. doi: 10.1111/jfd.13450. Epub 2021 May 30.
Pacific salmon (Oncorhynchus spp.) rearing in lakes and reservoirs above dams have been known to become heavily infected with an ectoparasitic copepod (Salmincola californiensis). Little is known about the factors that affect the parasite infection prevalence and intensity. However, previous research suggests that the parasite may negatively affect the fitness and survival of the host fish. The effect of water temperature, confinement and the density of the free-swimming infectious stage of S. californiensis, the copepodid, on infection prevalence and intensity was evaluated by experimentally exposing juvenile Chinook Salmon (O. tshawytscha). Infection rates observed in wild populations were achieved under warm water (15-16°C) and high copepodid density (150-300/L) treatment conditions. Infection prevalence and intensity were also significantly higher in larger fish. During the infection experiment, 4.5% of infected fish died within 54 days with mortality significantly related to copepod infection intensity. The potential for autoinfection was compared to cross-infection by cohabitation of infected fish with naïve fish. Previously infected fish had significantly greater infection intensity compared with naïve fish, indicating that infected fish can be reinfected and that they may be more susceptible than naïve fish.
在大坝以上的湖泊和水库中养殖的太平洋三文鱼（Oncorhynchus spp.）已知会受到一种外寄生桡足类（Salmincola californiensis）的严重感染。目前人们对影响寄生虫感染率和感染强度的因素知之甚少。然而，先前的研究表明，寄生虫可能会对宿主鱼的健康和生存产生负面影响。通过实验暴露幼年奇努克三文鱼（O. tshawytscha），评估了水温、限制和自由游动的传染性桡足类幼虫（Copepodid）的密度对 S. californiensis 感染率和感染强度的影响。在温暖的水（15-16°C）和高桡足类密度（150-300/L）的处理条件下，可以观察到在野生种群中观察到的感染率。在较大的鱼中，感染率和感染强度也显著更高。在感染实验期间，4.5%的感染鱼在 54 天内死亡，死亡率与桡足类感染强度显著相关。将自体感染与感染鱼与未感染鱼同居的交叉感染进行了比较。与未感染的鱼相比，先前感染的鱼具有更高的感染强度，这表明感染的鱼可以再次感染，并且它们可能比未感染的鱼更容易感染。
