The effects of a tsunami on abalone (Haliotis discus hannai), and sea urchin (Mesocentrotus nudus) populations in Otsuchi Bay, Japan, are reported. Changes in density and size composition of the two species are compared at three locations along nine transects in the inner, middle and entrance parts of Otsuchi Bay. The intensity of tsunami impacts, and degree of recovery differed among locations and species. Tsunami impacts on the abalone were greatest in the inner part of the bay, where density remains almost 0 inds./m2 even in 2015. However, clear changes in density and size composition of the abalone have not been confirmed in the middle and entrance parts of the bay until 2015. In the inner part of the bay, an increase in urchin density is attributed to continuous successful recruitment following the tsunami, and this phenomenon was considered as a factor for shrinkage of algal communities and the abalone population in the inner part.Special Issue（東日本大震災特集
