Comparison of fish assemblage structures between exposed and protected sandy beaches at Uchibo, Boso Peninsula, central Japan

摘要

Daytime sampling was conducted at Uchibo, Boso Peninsula, Japan in December 2014, and March, July and September 2015, to determine whether or not fish assemblage structures differed between exposed (Osawa, Hota and Hasama) and protected (Kazusaminato, Tadara and Nago) sandy beaches. Although some physical variables (wave height and turbidity) differed between the two beach types, no differences were found between the beach types in terms of either abundance of main fish prey (zooplankton, epifaunal and infaunal invertebrates) or fish assemblage structure (total numbers of species and individuals, species composition, individual numbers of the four most dominant species [except the mugilid Mugil cephalus cephalus], species and individual numbers of the two dominant feeding groups, and standard lengths of all species, including the five most dominant ones) throughout the study period. Because only the number of Mugil cephalus cephalus individuals differed significantly between the beach types, the protected beaches supporting greater numbers, sandy beach fish assemblage structures were generally considered similar between the two beach types, in spite of their beach type-related abiotic differences.