Limited effect of the massive tsunami caused by the 2011 Great East Japan Earthquake on the shallow sandy shore demersal fish assemblages in Sendai Bay

Abstract

We examined the effects of the 11 March 2011 tsunami event on demersal fish assemblages in the shallow (3–17 m) waters of Sendai Bay, Japan. Fish samples were obtained during the 7 yr before the tsunami, the year of the tsunami (2011), and in two subsequent years (2012–2013) using an identical sampling procedure. During the 10 yr, 5757 fish from 70 taxa were sampled during 301 tows. Although the tsunami reached 6 m in height in Sendai Bay, fish abundance, diversity, and species composition in samples immediately after the tsunami (2011) and in 2012–2013 were generally within the range of variability observed over the previous 7 yr (2004–2010). Moreover, the percent occurrence of species varied during the sampling period, but the composition of the dominant species after the tsunami was similar to that before the tsunami. Only the small dragonet species Eleutherochir mirabilis decreased in abundance in 2011 among the dominant taxa, although their abundance recovered in 2012 and 2013. Furthermore, Japanese flounder, Paralichthys olivaceus, increased in abundance after 2011. The reasons for these minimal effects on the shallow water demersal fish community are unclear. We can only speculate that the limited changes to habitat and the mobility of fish may have enabled the high survival rate of the shallow water fish assemblages in Sendai Bay during and after the tsunami. Thus, we conclude that the fish assemblages of the shallow sandy shore were highly resistant and resilient to unusual and extreme perturbations.

Impact of the great tsunami in 2011 on the quality of nursery grounds for juvenile Japanese flounder Paralichthys olivaceus in Sendai Bay, Japan

“…Therefore, the abundance would increase quickly. Furthermore, a temporal decrease in abundance of other predatory fish species on mysids after the tsunami (Okazaki et al ., ) would reduce predation pressure on the mysid. Larval and juvenile Japanese anchovy, the other main food, would originate from a pelagic and migratory adult from spring to autumn.…”

Consequences of “natural” disasters on aquatic life and habitats

“…Sea urchin densities decreased rapidly after the event, leading to an indirect increase in kelp abundance, however these impacts were not seen at sites that were afforded greater protection from the wave impact (Muraoka et al 2017). In other locations, the abundance, diversity, and species composition of shallow demersal fish assemblages did not appear to change significantly, which may be explained by the translocation or movements of more mobile fishes, enabling high survival rates (Okazaki et al 2017). Juvenile growth rates of a regional flounder species off Japan showed no change up to two years after the event (Kurita et al 2017).…”