Are the current IUCN category and CITES listing appropriate for the conservation and management of shortfin mako, Isurus oxyrinchus, in the North Pacific Ocean?

Abstract

In 2018, the ISC conducted a benchmark stock assessment with a future projection and concluded that the latest stock status of North Pacific shortfin mako was healthy and that its stock abundance would gradually increase within 10 years. Then in 2019, this species was categorized in the North Pacific Ocean as Vulnerable on the IUCN Red List and listed in Appendix II of CITES. The inconsistent outcomes are a controversial issue and raise a fundamental question on why different international organizations had different views on the stock’s current and future declines. To clarify the reasons, this paper reviews the risk assessment conducted by the IUCN and the process of CITES listing, and then, based on the assessment results in 2018, conducts a future projection that incorporates uncertainties in the population trajectory. This projection indicates that the population level does not meet the criteria for the IUCN category of Vulnerable and listing in Appendix II. The results suggest that the IUCN’s simplified methodology of assessment is inappropriate for long-lived, sexually dimorphic species, and that the mechanism of CITES listing is inappropriate from the scientific view of stock assessment because all global stocks, each with a different status, have been treated as one stock. This paper therefore concludes that the IUCN category and CITES listing are both inappropriate for the conservation and management of North Pacific shortfin mako and that such efforts should be implemented by tuna RFMOs based on stock assessment and future projection results derived from a suitable assessment model.