The Pacific saury (Cololabis saira) is a fish of commercial importance subject to unpredictable epidemics of infection by Pennella sp., a parasitic copepod. We analyzed the distribution of fish presenting with newly attached Pennella to determine the region and season in which Pennella first infect the fish. Pacific sauries migrate northward in the spring to spend the summer in the subarctic region, successively crossing the Subarctic Boundary (SAB) and the Subarctic Front (SAF). The fish then return to subtropical waters in the fall and overwinter there. Pacific sauries infected with Pennella were observed on both the north and south sides of the SAF from May to December. Newly attached Pennella, however, were observed mainly to the south of the SAF during the northward migration of the fish in May and June, and only to the south of the SAB during the southward migration in November and December. These results indicate that the intermediate host or hosts of Pennella inhabit the region south of the SAF, with infection of Pacific saury occurring during late fall and spring. Such information may assist in identifying the intermediate host(s).

中文翻译：

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Pennella sp。感染太平洋秋刀鱼的Cololabis saira（Brevoort，1856）（Teleostei：Beloniformes：Scomberesocidae）。北极前锋以南（Co足类：虹吸孔目科：Pennellidae）

太平洋秋刀鱼（Collolabis saira）是商业上重要的鱼类，易受Pennella sp。（一种寄生infection足动物）感染的不可预测的流行。我们分析了新附着的Pennella出现的鱼的分布，以确定Pennella首次感染鱼的区域和季节。太平洋秋刀鱼在春季向北迁移，在整个北极圈度过夏季，随后越过了北极圈界线（SAB）和北极圈前线（SAF）。然后，鱼在秋天回到亚热带水域并在那里越冬。5月至12月，在苏丹武装部队的南北两侧均观察到感染了Pennella的太平洋秋刀鱼。新附然而，在5月和6月鱼向北迁移期间，主要观察到Pennella在SAF的南部，而在11月和12月向南迁移时仅观察到SAB的南部。这些结果表明，Pennella的一个或多个中间寄主居住在SAF南部地区，在秋末和春季发生了太平洋秋刀鱼的感染。这样的信息可以帮助识别中间主机。