Abstract
Population dynamics of small pelagic fishes (SPF) and their management in Japan were reviewed for Japanese sardine Sardinops melanostictus, Japanese anchovy Engraulis japonicus, chub mackerel Scomber japonicus, and Pacific saury Cololabis saira. The catch and biomass of SPF generally showed decadal-scale variability with prominent species replacements since the 1900s. The causes of species replacements were generally associated with climatic/oceanic variability, particularly “regime shifts,” of which the 1988/89 regime shift was the most influential since the 1970s. Variability in the early survival rate is a key factor for population fluctuations, and the proposed hypothetical mechanisms of recruitment variability are summarized herein. Although overfishing during the 1990s and early 2000s prevented the recovery of Pacific stocks of sardine and chub mackerel, they have been recovering since the mid-2000s owing to strong year classes and reduced exploitation rates. The fundamental cause of overfishing was derived from a mismatch between investments in larger purse seine fleets during the 1980s and poor ocean productivity since the 1988/89 regime shift, when dominant SPF began to shift from sardine to anchovy. Recommendations for fisheries management of SPF around the Japanese Archipelago are proposed, considering climate change and naturally and drastically changing SPF populations.
Highlights
Population dynamics and Japan’s fishery management of the principal small pelagic fishes (SPF) around the Japanese Archipelago were reviewed on the basis of available information, including long-term trajectories of commercial catch, biomass, spawning stock biomass (SSB), recruitment, recruitment per spawning stock biomass (RPS, No./kg), fishing mortality coefficient (F), and exploitation rate (ER, catch weight/biomass)
In the Pacific Ocean, Pacific saury fishing grounds belonging to Japan and Russia are generally located within their exclusive economic zone (EEZ), whereas China, South Korea, and Taiwan harvest this species in international waters (Suyama et al 2016), i.e., the Convention area of the North Pacific Fisheries Commission (NPFC)
Overfishing during the 1990s and early 2000s prevented the recovery of the Pacific stocks of sardine and chub mackerel
Summary
Population dynamics and Japan’s fishery management of the principal small pelagic fishes (SPF) around the Japanese Archipelago were reviewed on the basis of available information, including long-term trajectories of commercial catch, biomass, spawning stock biomass (SSB), recruitment, recruitment per spawning stock biomass (RPS, No./kg), fishing mortality coefficient (F), and exploitation rate (ER, catch weight/biomass). The spawning season generally extends from winter to spring, except for anchovy, whose spawning period extends from spring to autumn Subarctic waters such as the Oyashio Current and Yellow Sea, and the northern areas of the Japan Sea and East China Sea are important feeding grounds for SPF during summer and autumn. In the Pacific Ocean, Pacific saury fishing grounds belonging to Japan and Russia are generally located within their exclusive economic zone (EEZ), whereas China, South Korea, and Taiwan harvest this species in international waters (Suyama et al 2016), i.e., the Convention area of the North Pacific Fisheries Commission (NPFC) This was formally established in 2015, and is responsible for stock assessment and management of commercially important species and the surrounding ecosystems (with the exception of tunas and salmons, for which other international organizations are responsible; Yatsu and Ye 2011). The somatic growth and maturation of SPF are affected by stock abundance (Table 1)
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