An impact and adaptation assessment of changing coastal fishing grounds and fishery industry under global change

Changes in fish distribution and migration patterns have occurred in mid- and high-latitude oceans worldwide in response to global change. Since the 1980s, the sea surface temperature (SST) of the Sea of Japan has increased significantly. The mechanisms behind these changes in migratory fish assemblages are difficult to determine from general capture fishery databases. This study collected a long-term dataset of set-net catches reported from Toyama Bay in western Japan to analyse catch compositions. The results indicated that in the coastal zone at the front of the Tsushima warm current and Liman cold current, increased SSTs have caused fluctuations both in the presence of cold-water and warm-water fish and in the timing of fishing seasons. Additionally, the results based on multi-dimensional scaling and cluster analyses showed that the study period can be divided into 5 clusters: (1) 1963–1964, (2) 1966–1972, (3) 1973–1998, (4) 1999–2006, and (5) 2007–2013; the similarity value was 89%. The boundaries between these clusters were similar to the timing of changes in SST, Pacific decadal oscillation, and North Pacific gyre oscillation. A species composition change analysis of these clusters showed that clustering was associated with changes in the intensities of the Tsushima warm current and Liman cold current. A northward expansion of low-latitude fish species, especially small- and medium-sized fish, was observed in Toyama Bay, similar to the expansion of high-latitude fish species into polar regions. Based on the principles of risk management and these research results, the adaptation strategies recommended in this study were differentiated into two categories: proactive adaptation and planned adaptation. (1) Establishment of pre-disaster adaptation capability: Proactive adaptation emphasizes countering the uncertainty in marine fishery production and improving the resilience of local communities. (2) Establishment of resilience during and after climate disasters: Planned adaptation can be used to manage uncertainty in the seafood supply by implementing adjustments in production and marketing and also to mitigate the impact of climate variation on the marine fishery industry and local coastal communities.