North Pacific Anadromous Fish Commission

Technical Report 17

Table of Contents

Effects of the Great East Japan Earthquake and Tsunami on Fisheries and Salmon in Iwate Prefecture

Authors:
Tsuyoshi Nagasaka and Yuichi Shimizu

Abstract Excerpt:
The 9.0-magnitude Great East Japan Earthquake (GEJE) occurred at 14:46 local time on 11 March 2011. The following tsunami swept away towns, buildings, cars, and even human lives on the Pacific coast of Iwate Prefecture. The tsunami reached the coast about 30 minutes after the earthquake occurred (Fig. 1a), and soon swept away buildings and cars (Fig. 1b). The fisheries in Iwate were also severely damaged and the hatchery enhancement program for chum salmon (Oncorhynchus keta), a most important fisheries resource in Iwate, was in a critical situation (Ogawa and Shimizu 2012; Goto 2018). The salmon fisheries yield occupies about 20% of all fisheries yield in Iwate Prefecture. Iwate has over 100 years of history for the hatchery enhancement program. The number of hatchery-released fry has increased gradually since 1971, and approximately 400 million fry are released annually since 1984 (Fig. 2). The number of salmon returns also increased with the increasing number of released fry, and it reached a peak (25 million fish) in 1996 (Fig. 2). The salmon resource depends on the hatchery enhancement program in Iwate. On the other hand, after the marked peak in 1996, it has been decreasing gradually, with notable decreases of 40% in 1998 and 60% in 2011, when compared to the average between 1983 and 2010 (Fig. 2). Why are adult returns decreasing? We estimate that a decreasing number of fry releases due to natural disasters, such as repeated earthquakes and typhoons, and changes of ocean environment have strong impacts on recent adult returns.

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

DOI:
https://doi.org/10.23849/npafctr17/160.163.

Citation

Nagasaka, T., and Y. Shimizu.  2021.  Effects of the Great East Japan Earthquake and tsunami on fisheries and salmon in Iwate Prefecture.  N. Pac. Anadr. Fish Comm. Tech. Rep. 17: 160–163.  https://doi.org/10.23849/npafctr17/160.163.