Characteristics of a sea louse (Caligus clemensi) epizootic in wild Pacific herring (Clupea pallasii)

Canadian Journal of Fisheries and Aquatic Sciences
By: , and 

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Abstract

We characterized a natural sea louse epizootic of Caligus clemensi and the effects of parasitism on Pacific herring Clupea pallasii in Port Angeles Harbor, WA, USA. Infestation prevalence on newly metamorphosed age 0 Pacific herring reached 100% prevalence by mid-August. At this time, the mean louse intensity was 4.6 lice/fish, and a positive correlation occurred between louse intensity and herring body length. The epizootic then waned, with infestation prevalence decreasing to less than 25% and the mean parasite intensity falling below 1 louse. While skin injuries were not detected, motile lice preferentially aggregated around head and anterior dorsal areas. However, louse tropism became evenly distributed over the body as the parasite intensity increased. Louse-induced mortality in herring was negligible in controlled experiments. These results indicate that Caligus clemensi epizootics reach high prevalence, but also fade from mid-summer to early fall. Due to the predominant presence of motile copepod stages, we suggest that the epizootic fades because lice complete their life cycle and dislodge from the host; however, multiple explanations for epidemic fading are possible.

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Publication type Article
Publication Subtype Journal Article
Title Characteristics of a sea louse (Caligus clemensi) epizootic in wild Pacific herring (Clupea pallasii)
Series title Canadian Journal of Fisheries and Aquatic Sciences
DOI 10.1139/cjfas-2023-0070
Volume 80
Issue 12
Year Published 2023
Language English
Publisher Canadian Science Publishing
Contributing office(s) Western Fisheries Research Center
Description 10 p.
First page 1847
Last page 1856
Country United States
State Washington
City Port Angeles
Other Geospatial Pacific Ocean
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