The global landings from the capture fisheries have increased dramatically over the past few decades. This has been achieved partly through more fishing activity with additional people and larger fleets, but more importantly through the continuous development of harvesting technology which has resulted in much higher efficiency of vessels and gears.
New technology has had a major impact on pelagic fishing. Pelagic trawls and purse seines have revolutionised the capture of schooling species like sardines and anchovies (clupeoids), mackerels (scombroids), and horse mackerel (carangids). These methods depend on sophisticated acoustic methods for detecting fish. Sonars and echosounders have been developed which indicate the quantity of fish as well as the location. These instruments are used to search for pelagic fish concentrations and in aimed fishing to manoeuvre the gear to intercept schools. Pelagic trawls and purse seines routinely take large catches of hundreds of tonnes.
The introduction of synthetic materials like polyethylene has greatly improved the durability of nets and has reduced costs. The development of demersal trawls has led to new more efficient designs of gear. Other innovations include radio and satellite navigation to locate fishing grounds, fish aggregating devices which attract fish to be more accessible to fishers, and improvements in vessel technology such as the change from side fishing to stern trawling. In small-scale fisheries, outboard engines have replaced manpower and sails, again increasing the efficiency of fishing operations.
The continual improvement in catching power has resulted in the present situation where many fisheries are overexploited. In the past, fishing gear research was primarily concerned with increasing catches, but now the emphasis is on better management and ensuring sustainable yields. Problems such as excessive discarding and the bycatch of unwanted fish are being addressed through the development of gears with improved selectivity. Technical measures such as minimum mesh sizes are used in many fisheries, but on their own they are insufficient to ensure sustainability and containment of fishing effort is still necessary. However, the effective fishing effort per vessel or other unit will inevitably increase through new technology and methods of operation, and exploitation rates in most fisheries are still much too high.
Traditionally, fishery management was mainly concerned with the biology of fish populations and how to optimize the yield. Wider issues now have to be considered, in particular the effect of fishing on the environment. These issues include the disturbance of bottom fauna by trawling, bycatches of sea mammals and seabirds, and pollution through lost or abandoned fishing gear. The marking of gear to indicate ownership is one initiative which might discourage the deliberate abandonment of nets. More generally, an important objective of current research is to develop fishing methods with more environmentally friendly characteristics.
Recent work has much improved understanding of how the species and size composition of the catch may be controlled. New designs of gear facilitate the escape of small fish and separator trawls have been developed which sort the catch by species within the gear. The turtle excluding device (TED) is a successful example of how gears can be modified to avoid unwanted bycatches. However, it can be difficult to persuade fishers to adopt more selective fishing methods. There is need for suitable training initiatives and incentives to achieve the longer-term benefits of environmentally friendly fishing. The FAO Code of Conduct for Responsible Fishing sets out the important principles and action to promote their adoption in practice is urgently required.
Another problem is the mortality of fish which are not taken by the fishers but are nevertheless killed by encountering the gear. Fish escaping through meshes may be fatally damaged, and lost gear (especially gillnets) continue to catch fish for some time. The extent of this unaccounted mortality is not well understood and further research is needed to reduce the problem.
Of all the food industries, fishing is one of the highest energy users per unit of protein produced, although the great range in production efficiency between fishing methods must be noted. Energy efficiency is an important issue for technological development, although it is currently receiving less attention since fuel prices are relatively low. The presently favourable cost of fuel cannot be expected to continue indefinitely, and further development of energy efficient fishing methods is still necessary.
There is reasonable agreement on the management measures which should be adopted to optimize the economic return from fisheries. They include containment of fishing effort, and controls on fishing methods to avoid unwanted bycatches or undesirable environmental effects. However, such measures will not work unless they are observed by fishers or enforced by the competent authority. The control of fishing activities at sea is difficult, but new technology can help for example through satellite surveillance of fishing vessels. Future developments in monitoring, control and surveillance methods (MCS) can be expected to strengthen the hand of governments in regulating the fisheries more effectively.
It is concluded that the continuous evolution of fishing methods combined with growth in populations, industrial capacity and the number of fishing vessels is likely to maintain the current overfishing of most stocks. Unless effective measures are taken to contain the level of fishing mortality, the mismatch between the fishing power of fleets and the sustainable yield of fisheries will get worse. The consequences of inadequate management are that the production of capture fisheries will be less than optimum, perhaps much less and food security will be compromised.