Over 120 years of landing trends in Japan, for the commercially exploited shark species, Squalus suckleyi

Abstract

Landing trends denote actual removal of a species by fisheries and may be a useful index of stock biomass dynamics, but accurate records for North Pacific spiny dogfish (Squalus suckleyi) landings in Japan are only available for 1952–1967. We used official Japan statistical yearbook data and bootstrap methodology to estimate landings of Pacific spiny dogfish, for 1894–1951 and 1968–2013, by prefecture. The landing estimates indicate that this species has been continuously exploited around Japan for over 120 years, since at least 1894. The landing trends could be divided into four periods: stable, low catch (1894–1919); increasing catch (1920–1949); decreasing catch (1950–1963); and relative stability (1964–2013). The trend in Pacific spiny dogfish landings appears to have been strongly influenced by societal demand, as supported by unit price trends for sharks. This result suggests that determinations of stock status based only on landing trends are inadequate for this species. After 1990, estimates of Pacific spiny dogfish landings ranged from 2800 to 4500 mt annually. A large proportion (52.7–74.7%) of the annual landings of this species were made by Hokkaido and Aomori prefectures, which are located near important habitat for this species in the northwestern Pacific. Thus, these regions are especially important for effective management and sustainable exploitation of the Pacific spiny dogfish stock in Japan.