The signature of climate-scale impacts on marine ecosystems is written in sources as diverse as the paleo-ecological record and the history of global fisheries. Analyses of sea floor sediments reveal changes in plankton communities with alteration in climate regimes, while variations in the abundance of pelagic fishes over millennia have been traced through scale deposition rates in undisturbed ocean basins. Changes in these fish communities considerably pre-date human harvesting activities for these species and point to a dominant role of climate variability and change in the dynamics of these systems. Historical documentation of catch in some of the major fisheries of Europe and Asia extends over many centuries and in these records rest clues to the waxing and waning of fish stocks in response to climate and the effects of human activities, such as fishing. The fortunes of the Hanseatic League in Medieval Europe were directly linked to trade in fishery resources, notably cod and herring, which varied with climatic conditions (Cushing, 1982; Kurlansky, 1999). The potential consequences of climate change for earth systems, the effects of other anthropogenic impacts on marine ecosystems, and the possible interaction between climate change and human activities affecting the oceans are now broadly recognized and are of vital concern.