Globally, fishing vessels (including inland vessels) consumed 53.9 metric tonnes of fuel in 2012, emitting 172.3 MT of CO2, which is about 0.5 percent of total global CO2 emissions that year. While fishing vessels are more efficient in recent years, significant opportunities exist for reduction in fuel use and greenhouse gas (GHG) emission in capture fisheries. A reduction of vessel emissions by 10 to 30 percent is achievable with efficient engines and larger propellers, better vessel shape and hull modifications, as well as use of fishing gears that require less fuel for harvesting (e.g. multi-rig gear, efficient otter boards, off-bottom fishing, high-strength materials, large mesh sizes and smaller diameter twines). The first step of emission reduction in capture fisheries is the auditing of energy use by fishing vessels to systematically evaluate the potential cost and environmental impacts of fuel saving practices. An energy audit project carried out by FAO in Thai trawl fisheries revealed that the judicious use of the throttle to regulate engine rpms was identified as the simplest option and was estimated to reduce fuel consumption by up to 35 percent when steaming. The use of a fuel flow meter and regular removal of hull fouling organisms were identified as low cost options that can reduce fuel consumption by an estimated 5 percent when fishing. It is recommended that similar projects be carried out in other developing countries to fully avail simple and cost-effective options for fuel-saving and reduction of emission. Aquaculture is not a major global producer of GHG, with emissions amounting around 7 percent of those from agriculture; the emissions originate from the production of raw feed materials and transport of raw materials and finished feeds to the farms. Despite its low contribution, there is room for reducing emissions from this subsector by improving technological efficiency, reducing reliance on fossil fuel, replacing fish-based feed ingredients and improving feed conversion rates. Combining these approaches would result in a reduction of 21 percent in CO2 emission per tonne of fish produced. In support of the mitigation efforts, a joint FAO-Global Salmon Initiative workshop on Reducing Feed Conversion Ratios in the Global Aquaculture to reduce carbon and other footprints and increase efficiency (911 November 2015, Liberia, Costa Rica) led to the publication of a tool for quantifying greenhouse gas emissions arising from aquaculture together with the workshop report. The publication also provides an overview of concerted actions to reduce Feed Conversion Ratios in the global aquaculture industry and explores potential transfer of feed and feeding technologies and lessons learn from salmon farming to other species such as carps, catfishes, tilapia and marine shrimps.