Effects of environmental changes on larval and juvenile fish fauna in the surf zone following the Great East Japan Earthquake in southern Iwate, Japan

Abstract

　The sandy surf zone at Urahama beach was substantially altered on 11 March 2011, as a result of a powerful tsunami and land subsidence. Although the zone disappeared immediately after the tsunami, a rejuvenated sandy beach and intertidal area emerged a few months later. Prior to the tsunami, 9 orders, 27 families, and 41 species of larval and juvenile fish were collected using a seine net from January 2003 to December 2005. The dominant species of larval and juvenile fishes primarily comprised eurythermal and cold-water species, reflecting the geographical characteristics of the larval and juvenile fish fauna. Nonmetric multidimensional scaling results revealed seasonal changes in the species composition. Post-tsunami, at least 44 species of larval and juvenile fishes were collected during 2012–2015, with this collection indicating changes in species composition and an increase in the diversity index. These findings were supported by cluster analysis results, based on Jaccard’s coefficient of community, and the ecological characteristics of the dominant species. Overall, these results suggest that environmental changes, particularly the increased introduction of stones and seaweeds in the new intertidal area, markedly influenced changes in larval and juvenile fish fauna.