First record of red tide due to the harmful dinoflagellate Karenia mikimotoi in Hakodate Bay, southern Hokkaido, in autumn 2015

Abstract

Red tides of the fish-killing dinoflagellate Karenia mikimotoi were recorded in Hakodate Bay for the first time in northern Japan during mid-October to late-November 2015. Mortalities of chum salmon Oncorhynchus keta, Japanese common squid Todarodes pacificus and Pacific abalone Haliotis discus hannai were observed during the mass occurrences of K. mikimotoi. The red tides of K. mikimotoi (3,200.11,500 cells/mL) were found at a temperature range between 9.9 and 15.7°C and a salinity range between 31.8 and 32.2. The northward expansion of occurrence area of K. mikimotoi is thought to be related to natural dispersal by the Tsushima and/or Tsugaru warm currents or by anthropogenic transportation via ships' ballast water.