Because we are concerned about what might be the local and regional effects of and responses to a global climate change, there is a need at the outset to identify how well societies have in the past dealt with local climate-related environmental changes, regardless of cause. Such an identification will provide researchers as well as policymakers with societal baseline data. To know how best to prepare for future changes, we must know how well we cope with present-day changes, identifying societal strengths and weaknesses. To accomplish this, the “forecasting by analogy” approach is used, not to forecast future states of the atmosphere or the ocean, but to forecast how well prepared societies are to cope with changes in abundance or availability of living marine resources, regardless of the causes of those regional changes.

Fish populations are influenced by many elements of their natural environments during all phases of their life cycle. Subtle changes in key environmental variables such as temperature, salinity, wind speed and direction, ocean currents, strength of upwelling, as well as predators, can sharply alter their abundance, distribution and availability. Human activities can also affect the sustainability of these populations through, for example, the application of a variety of management schemes or new technologies, each of which could have a different (either beneficial or adverse) impact on the state of the fishery.

Interactions within the marine environment are acknowledged to be extremely complex.