Climate change, regime shift and stock management

Abstract

As more and more data of long-term variability in marine organisms from phytoplankton to predatory fish accumulate, a persistent pattern of the interdecadal and global scale, regime shift, is emerging. Many of the fish populations are growing and declining rhythmically with a high degree of synchrony. A skyrocketing improvement in chum salmon's rate of return to Japan as brought about by a technological innovation is now unacceptable and it seems to embody the regime shift. Abundant evidence in support of the regime shift has been given recently for the variability in climate-ocean system which suggests that climate change may be the driving force linking the variations in marine populations. There are some forerunning studies that lead to mechanisms causing global concurrence in ocean enrichment. In the traditional population dynamics that has underlain the current stock management regime and enhancement programs, it is assumed that a fish population is in equilibrium with the fishing effort under average environmental conditions. Change in biomass due to environmental variations is regarded as a noise and hence an unfished population remains unchanged. The theory, however, has turned out inconsistent with the real world and it needs be examined.