Abstract
The huge tsunami associated with the 2011 Great East Japan Earthquake severely impacted the ecosystems on the Sanriku coast of Japan. The life history traits of ayu, Plecoglossus altivelis altivelis, which have a one-year amphidromous life history, were investigated by otolith analyses in two rivers of the Sanriku coast just after the tsunami compared with results before the tsunami to reveal the immediate impact of the tsunami. Hatching date compositions differed between the upstream migrants before and after the tsunami. The migrants after the tsunami were solely composed of fish hatched during October and November, whereas the migrants before the tsunami were mostly composed of fish hatched in September. Discrepancies between the hatching dates of the migrants and drifting larvae (hatched larvae) indicate that selective mortality of early-hatched fish occurred during the tsunami. Differences in otolith Sr:Ca ratios between upstream migrants before and after the tsunami suggest that fish surviving the tsunami inhabited saline water and early-hatched fish that inhabited the estuary decreased selectively in number because of the severe erosion around the river mouth. The oceanic growth period shortened in accordance with the change in hatching date. These results show that the tsunami drastically altered the ecology of P. altivelis altivelis on the Sanriku coast.
Highlights
Tsunami are a recurring natural hazard that have repeatedly disturbed coastal ecosystems, such as sandy beaches, seagrass beds, coral reefs, mangrove forests and near shore terrestrial ecosystems (Cochard et al 2008; Whanpetch et al 2010; McAdoo et al 2011)
The 2011 upstream migrants were composed completely of fish that hatched after October in both rivers, whereas fish that hatched in September constituted the majority of upstream migrants before the tsunami (Fig. 3)
Our results show typical upstream migration of Plecoglossus altivelis altivelis despite the huge tsunami associated with the 2011 Great East Japan Earthquake
Summary
Tsunami are a recurring natural hazard that have repeatedly disturbed coastal ecosystems, such as sandy beaches, seagrass beds, coral reefs, mangrove forests and near shore terrestrial ecosystems (Cochard et al 2008; Whanpetch et al 2010; McAdoo et al 2011). It has been suggested that tsunami have long-lasting effects on coastal ecosystems and that the restoration process is long-standing (Whanpetch et al 2010; Jaramillo et al 2012). The tsunami associated with the Great East Japan Earthquake, with a moment magnitude of 9.0, occurred on 11 March 2011 and struck the Pacific coast of northeastern Japan (Mori et al 2011; Ozawa et al 2011; Simons et al 2011). The tsunami extensively inundated over 400 km of the coastal area and devastated a large area of the northeastern part of Japan together with coseismic subsidence and eastward movement of the coast (Mori et al 2011; Simons et al 2011). The Sanriku coast is a ria, composed of many steep narrow bays; the tsunami was amplified to about 40 m in maximum runup height and severely destructed the coastal topography and structures (Mori et al 2011; Tanaka et al 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
