A new briefing distils the key findings from the recently released Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5), revealing the growing threat of climate change to fisheries and aquaculture. Climate change and acidification are altering ocean ecosystems in profound ways, with consequent impacts on fisheries and aquaculture. Projected impacts of climate change on fisheries and aquaculture are negative on a global scale. Major impacts include displacement of stocks and, for aquaculture, mortality of shellfish from acidic water. Impacts of climate change and ocean acidification are generally exacerbated by other factors such as overfishing, habitat loss and pollution. This is contributing to an increase in the number of ‘dead zones’ in the ocean, as well as to an increase in harmful algal blooms. Coral reef ecosystems are declining rapidly, with the risk of potential collapse of some coastal fisheries. Incidences of coral bleaching are likely to increase. Aquaculture may be affected through reduced catches of feed-fish and increasing severity of tropical storms and flooding.