Recreational fisheries are also becoming increasingly important. In contrast to marine fisheries, bycatches and discarding are not significant problems, practically all fish that are caught are consumed.
Estuaries, which may be flanked by salt marshes or mangrove, are usually the areas of highest natural productivity. Their influence extends well out into coastal seas and even, in some instances, the open ocean. Many different species of fish move into the estuaries to feed, some enter to breed and others, such as eel and salmon, pass through on spawning migrations.
The world has some 269 000 km of main river channels, but the water held in reservoirs is about seven times the standing volume in the rivers. The total area of lakes is just over four times that of reservoirs. In addition to capture fisheries, most aquaculture production originates in freshwater and the artificial enhancement of inland waters is becoming increasingly common to improve or restore production.