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Assessment of the timing and degree of smolt development in southern populations of masu salmon Oncorhynchus masou

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Title: Assessment of the timing and degree of smolt development in southern populations of masu salmon Oncorhynchus masou
Authors: Inatani, Yu Browse this author
Ineno, Toshinao Browse this author
Sone, Shiori Browse this author
Matsumoto, Naoto Browse this author
Uchida, Katsuhisa Browse this author
Shimizu, Munetaka Browse this author →KAKEN DB
Keywords: Autumn
masu salmon
Miyazaki Prefecture
Issue Date: Sep-2018
Publisher: John Wiley & Sons
Journal Title: Journal of fish biology
Volume: 93
Issue: 3
Start Page: 490
End Page: 500
Publisher DOI: 10.1111/jfb.13647
PMID: 29931678
Abstract: The present study assessed whether non-anadromous masu salmon Oncorhynchus masou in Miyazaki, southern Japan, smoltify, and if so, at what time of the year. Yearling O. masou of Miyazaki and an anadromous population from Hokkaido, northern Japan, were reared in hatcheries in their respective regions and sampled monthly from February to June to examine the spring smoltification period. The Hokkaido population showed a peak of gill Na+-K+-ATPase (NKA) activity in May, which was accompanied with an increase in mRNA levels of the seawater (SW)-type NKA alpha subunit, nka1b. Increases in gill NKA activity and nkaa1b levels were not seen in Miyazaki populations. Transferring yearling Miyazaki population to 70% SW (salinity of 23) in mid-April resulted in an increased serum osmolality over 4 days. These results suggest that they do not smoltify in their second spring. Next, profiles of gill NKA activity and its subunit mRNA levels in under-yearling Miyazaki population in the autumn were examined. Two phenotypes differing in body color during this period were categorized as parr and smolt-like fish. Smolt-like fish had higher gill NKA activity than parr in December while there was no significant difference in gill nka1b levels. Smolt-like fish acclimated to 70% SW better than parr as judged by lower serum osmolality. However, serum osmolality in smolt-like fish did not return to the basal level 7 days after transfer to 70% SW, suggesting that their hypo-osmoregulatory ability was not fully developed to a level comparable to anadromous populations of this species. The present study suggests that, if O. masou in Miyazaki go though a smoltification process, it occurs in its first autumn instead of the second spring and is less pronounced compared with anadromous populations.
Rights: This is the peer reviewed version of the following article: Inatani Y, Ineno T, Sone S, Matsumoto N, Uchida K, Shimizu M. Assessment of the timing and degree of smolt development in southern populations of masu salmon Oncorhynchus masou. J Fish Biol. 2018;93:490–500, which has been published in final form at This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.
Type: article (author version)
Appears in Collections:水産科学院・水産科学研究院 (Graduate School of Fisheries Sciences / Faculty of Fisheries Sciences) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 清水 宗敬

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