Mangrove forests, sea grass beds, coral reefs and estuaries all contain enormous biological diversity which provide employment for men, women and children. In addition to fishing, men may engage in charcoal production, the cutting of wood for lumber or firewood, the collection of material for making thatch roofs or subsistence-oriented hunting and trapping. Indeed, it probably is fair to say that many if not most fishers also are employed in other activities. Fishing itself is a diverse occupation. Most fisheries of Southeast Asia are both multispecies and multigear in nature.
Many species also have a distinct seasonal characteristic.
The seasonal availability of one species gives way to that of another, either in one locale or another. Like their prey, fishers are mobile and often follow stocks over great distances. In other cases, fishers switch gears on a seasonal basis, harvesting various pelagic or demersal species depending on their availability. This variability in species, gear and season is a key factor in understanding fishing as an occupation that sustains households and communities. Fishers exploit not only local ecosystems but also more distant ones, and only rarely rely on one gear or species.