North Pacific Anadromous Fish Commission

Technical Report 11

Table of Contents

Effects of Duration of Net-pen Acclimation and Timing of River Stocking on Early Growth and Adult Return of Chum Salmon along the Pacific Coast of Honshu, Japan

Authors:
Miwa Yatsuya, Kei Sasaki, Yuichi Shimizu, Katsuhiko Ohta, Kodai Yamane, Yuichiro Yamada, Shunsuke Moriyama, Yoshitomo Nagakura, and Hideki Nikaido

Abstract Excerpt:
The number of chum salmon (Oncorhynchus keta) returning to the Pacific coast of Honshu, Japan, in the southernmost part of this species’ distribution, has decreased notably in recent years. One reason is the decline in stocked fry following the tsunami disaster of March 2011; another possible reason is the changing coastal environment. A recent study pointed out that warm water during the coastal residence period of juvenile chum salmon could be negatively affecting their early survival off Iwate Prefecture, northeast Honshu, Japan (Wagawa et al. 2016). To adapt to the changing coastal climate, we should reconsider the release timing of stocked salmon fry from rivers. Along the Pacific coast of Honshu, however, salmon fry are also stocked from net pens in near-shore areas, as well as from the rivers, because of local geographic conditions: a deeply indented rias coastline has developed in this area, and many of the small inlets and bays are suitable for net-pen acclimation. Net pens can supply the fry capacity of hatchery ponds and maintain hatchery fry densities at the appropriate level, but there are costs for feeding fry and maintaining the pen nets. To facilitate cost-effective fry production and improve adult return of chum salmon, we modified the present stocking program and developed new strategies, especially focusing on the duration of net-pen acclimation and the timing of river stocking.

*This is the first paragraph of an extended abstract. Download the full abstract below.

DOI:
https://doi.org/10.23849/npafctr11/127.128

Citation

Yatsuya, M., K. Sasaki, Y. Shimizu, K. Ohta, K. Yamane, Y. Yamada, S. Moriyama, Y. Nagakura, and H. Nikaido.  2018.  Effects of duration of net-pen acclimation and timing of river stocking on early growth and adult return of chum salmon along the Pacific coast of Honshu, Japan.  N. Pac. Anadr. Fish Comm. Tech. Rep. 11: 127–128.  https://doi.org/10.23849/npafctr11/127.128