Conceptual framework of the relationship between population size, sustainable harvest and global conservation status. The harvest that took place between A and B, C and D, and E and F, could be considered sustainable, whereas it is unsustainable between B and C and D and E. The global threat assessment based on two of the IUCN threat level criteria (population size and declining populations) are not tightly linked to harvest sustainability (modified after Yamaguchi 2014).