Extractive activities such as fisheries are not only depleting fish stocks of global importance but are also restructuring key ecosystems. Recent studies reveal that climate change is already having an impact on fisheries, in particular, warmer ocean temperatures are driving marine species towards cooler, deeper waters and this, in turn, has affected global fisheries catches. The debate on the sustainability of fisheries has moved to a global level over the past 20 years as fisheries have become recognised as a major driver of ecological and evolutionary change in the world's oceans. The global demand for seafood is increasing, driven in part by a growing population and rising incomes in countries such as China and India. A key problem in global fisheries is that much of the world's catch, and a large fraction of its biodiversity, resides in regions that urgently require increased food production and employment, but that have little capacity for scientific assessment and management controls.