Geographical distribution and seasonal occurrence of Myxobolus kisutchi (Myxozoa: Myxosporea) in the central nerve tissues of chinook [Oncorhynchus tshawytscha] and coho [O. kisutch] salmon in the Columbia River [USA] and its vicinities
2006
Urawa, S.(National Salmon Resources Center, Sapporo (Japan)) | Harrell, L. | Mahnken, C.W. | Myers, K.
The myxosporean parasite Myxobolous kisutchi Yasutake and Wood, 1957 infected in the medulla oblongata and spinal cord of Chinook (Oncorhynchus tshanytscha) and coho (O. kisutch) salmon. The parasite occurred in restricted areas of the Columbia River basin and its vicinities (Minter Creek and Chehalis River) in Washington, but not in other major Chinook salmon populations in North America and Asia. The prevalence of parasite spores in Chinook salmon smolts migrating down through the McNary Dam in the Columbia River was 20-37% in May (spring type), dropped to 1.3-1.7% in June (mainly fall type), and increased again to 29% in July (fall type). The prevalence of spores in adult Chinook salmon captured in the lower mainstream of the Columbia River was 43-65% for spring runs, but lower (8-11%) for fall runs. Among juvenile coho salmon reared at the Minter Creek Hatchery, the spores of M. kisutchi first appeared in June, and the prevalence increased to 97% in July, being sustained at almost 100% until the smolt stage in the next spring. The parasite was redescribed based on fresh specimens.
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