Effects of seawater temperature fluctuations on local communities through kelp production in the Pacific coastal area of eastern Hokkaido, Japan

Abstract

Data on the landing value for each of the eight fisheries commodities in small-scale coastal fisheries in Nemuro City was collected and analyzed to understand the importance of kelp fishery in local communities along the Pacific coast of eastern Hokkaido. Over the past 25 years from 1991 to 2015, a trend in small-scale coastal fisheries in the region has significantly varied. However, in all year groups, the landing value of the kelps accounted for about 40% of its total value, indicating no significant change in its importance. The kelp fishery always has a profit center within the small- scale fisheries operations in the region. The influences of seawater temperature and the physical environmental factors of the seafloor on kelp production were investigated using GIS. Mean seawater temperatures in July, September, and October of the year before the harvest negatively correlated with the kelp harvest in Nemuro City from 2006 to 2014. The kelp length was mainly explained by the water temperatures in September and July of the year before the harvest, bottom current velocity, and water depth. These results indicate that the water temperature during summer and the seafloor physical environment have significant effect on kelp growth. Recent increases in seawater temperature along the Pacific coast of eastern Hokkaido during summer would significantly impact the local socio-economy through reduced kelp production.