Management of declining Japanese sardine, chub mackerel and walleye pollock fisheries in Japan

Effects of process and/or observation errors on the stock–recruitment curve and the validity of the proportional model as a stock–recruitment relationship

“…Yatsu et al [27,28] and Ishida et al [29] adapted modified Ricker models that incorporate environmental factors, and proposed SRR models for Japanese sardine. However, those approaches involve serious mistakes when the true SRR model does not have a density effect, because they assume a priori that a density-dependence mechanism exists in the relationship between R and SSB.…”

“…Yatsu et al [27,28] and Ishida et al [29] have adapted a modified Ricker model that incorporated environmental factors and proposed SRR models for Japanese sardine. However, Sakuramoto et al [30] noted that the SRR data from 1988 to 1991 should be removed from the analysis of Japanese sardine, because the prevailing environmental conditions caused the data for these 4 years to be outliers.…”

Life-history traits of walleye pollock, Theragra chalcogramma, in the northeastern Japan Sea during early to mid 1990s

“…The poor condition of fish in the northern Japan Sea population may increase the difference in r between this population and other populations. The northern Japan Sea population has decreased in spawning biomass for the last two decades and recently suffered a severe population decline due to prolonged recruitment failures (Ishida et al, 2009). Although recruitment variability in this population is strongly related to winter environmental conditions (Funamoto, 2007), the low potential capability for population recovery suggests that we should have been more conservative when exploiting the spawning population.…”

Rebuilding of depleted fish stocks through an ecosystem approach to fisheries

“…Ishida et al (2009) reviewed the stock status and fishery management of three species off Japan: Japanese sardine (Sardinops melanostictus), chub mackerel (Scomber japonicus), and walleye pollock (Theragra chalcogramma). They considered seven of the twenty operational objectives identified by for an ecosystem approach to fisheries: (1) improving the decision-making framework, (2) priority setting or allocation, (3) maintaining biological diversity (here, defined as age diversity), (4) maintaining reproductive capacity, (5) reducing uncertainty and risk, (6) protecting selected marine areas, and (7) monitoring and indicators.…”

“…Worldwide progress toward development of operational objectives is sparse and uneven and new procedures must be developed to involve stakeholders in the decision-making process. As demonstrated by Ishida et al (2009), failure of stakeholders to understand and support management objectives undermines the ability of fishery managers to make progress toward rebuilding some Japanese fish stocks, even when the potential for large societal benefits of successful rebuilding appear obvious to fishery scientists.…”