Although a small global contributor, capture fisheries have a responsibility to limit GHG emissions as much as possible. Eliminating excessive fishing capacity and over-fishing; improving fisheries management; reducing post-harvest losses and increasing waste recycling will decrease the sectors’ CO-, emissions and improve the resilience of aquatic ecosystems. Other technical solutions to reduce fuel use might include shifting towards static fishing technologies and to more efficient vessels and gears. In some cases, win-win conditions could be identified, where reduced fuel-use strategies would link with reducing fishing effort, improving returns to vessels, safeguarding stocks and improving resilience to climate change (FAO, 2008).
A significant reduction of GHG emissions in capture fisheries and aquaculture can be achieved by reduction in energy consumption; use of fuel-efficient fishing methods; enhancing fuel efficiency in fisheries and aquaculture operations; integrated farming; and better feeds and feed management.
Reducing energy consumption
In capture fisheries, the vessel and gear are two main sources of energy consumption. Stationary gears consume less energy compared to mobile gears as energy consumption is limited to cruising up to the fishing ground in the former while it is for both propulsion and fishing in the case of latter. The choice of vessel design, size of engine and type of propeller determines fuel efficiency. Proper vessel length to width ratio, smooth hull painting and fairing, bulbous bows, high efficiency internal combustion engines, and larger diameter propellers with nozzles are some of the important features for a highly fuel-efficient vessel. For fishing gears, especially towed fishing gears, the use of efficient otter boards, off-bottom fishing, high-strength materials, large mesh sizes, and smaller diameter twines are some of the measures that reduce fuel consumption. Opportunities for reducing dependence on fossil fuel exist in usage of renewable energy systems such as wind and solar-powered generation of electricity.
Use of low impact fuel efficient fishing methods and gears
Fishing gears have varying degr ees of impact on marine ecosystems. Towed gears like dredges and otter board trawls affect the bottom where a contact with the fishing gear components and the bottom occurs. Seines interact with the bottom surrounded by the net and herding ropes. Stationary fishing gears have minor effect on the bottom habitats. Off-bottom fishing gears like pelagic trawls and purse seines have little or no bottom impact. Gill nets, long lines, pots and traps comprise fishing gears with low energy use.
Enhancing fuel efficiency of fisheries and aquaculture operations
Fisheries management has a great impact on all aspects of fish production, especially in capture fisheries and can therefore affect efficiency of fuel use. Management measures that reduce overall fishing effort and improve stock abundance make significant contributions to fuel efficiency in capture fisheries. Fuel efficiency and GHG emissions from fisheries should be considered as an integral part of fisheries management to sustainably reduce fuel use and GHG emission in fisheries. Area closures are a widely applied measure that can contribute to ensuring high and sustainable stock biomass, and therefore fuel efficiency.
In the case of capture fisheries, through use of efficient engines and larger propellers in fishing vessels, as well as through improving vessel shapes and other hull modifications and by reducing the mean speed of vessels, 10-30 % reduction can be achieved. In the case of fishing gears, switching from highly fuel intensive methods to low impact fuel efficient methods that require less fuel would reduce GHG emissions.
In aquaculture, GHG emissions are greatest in intensive production of finfish and crustaceans, which is heavily reliant on feeds and aeration. Integrated food production systems such as that of fish with rice, and shrimp-mangrove cultivation can substantially reduce overall GHG emissions from aquaculture production
Better feeds and feed management
There are also opportunities to reduce GHG emissions in aquaculture, which include improved technologies to increase efficiency in the use of inputs, greater reliance on energy from renewable sources, improving feed conversion rates, and switching from feed-based on fish to feed made from crop-based ingredients. The integration of pond aquaculture with agriculture is also a potential option for reducing fuel consumption and emissions.