Aquaculture can play an integral role in integrated farming systems. Such systems combine fish production, animal husbandry, waste treatment, and agriculture in one operation. The best-known examples of such operations today are in Europe and Asia, sustained by large inputs of labor, feed and fertilizer supplements. Societies interested in integrated farming systems to increase food production and employment opportunities without the use of imported manufactured supplements and feed would do well to survey the techniques and designs of ancient Hawaiian aquaculture.
No one knows for certain when fishponds were first constructed in but they were probably in use as early as the 14th century. When Captain James Cook reached Hawaii in 1778, there were approximately 360 fishponds producing some 900,000 kg of fish per year. By 1985 only 7 ponds remained in use. It is estimated that the yields from the Hawaiian fishpond systems operated before the arrival of the Europeans would be on par with most contemporary extensive aquaculture systems; yet the traditional Hawaiian fishponds did not receive fertilization from animal or human wastes of any kind. Ponds were fed with cut grass, mussels, clams, seaweeds, and taro leaves.
Four basic types of fishponds were used by the ancient Hawaiians: freshwater taro ponds, other freshwater ponds, brackish water ponds and seawater ponds. These fishponds spanned the natural salinity range of water. Pollution in the form of sewage, rubbish and offal was prohibited by religious sanctions.
The freshwater taro fishponds, located in the uplands, were the most integrated with taro cultivation. In many cases taro was planted in mounds within the fishponds, permitting the fish to feed on the insects infesting the plants, and the ripe leaf stems. This practice generated an additional benefit: the taro "pruned" by the fish grew more luxuriantly and had fewer pests than taro grown without fish. Freshwater fish such as mullet, silver perch and Hawaiian gobies, as well as freshwater prawns and green algae (spirogyra spp. and Cladophora spp.) were grown in these ponds.
Other freshwater ponds were created from natural ponds and lakes found close to the shore. All ponds had connections to the sea, either by natural streams or by irrigation ditches. These "freshwater" ponds would have been partially brackish due to tidal action. Fish such as mullet, silver perch, Hawaiian gobies, and milkfish who tolerate both fresh and brackish water, were raised in these ponds. The Hawaiians stocked these ponds by catching fish in shallow shoreline areas and transporting them in large water-filled gourds.
Brackish-water ponds were coastal bodies of water that had either been stranded due to natural changes in sea level or isolated through human formation of embankments. These ponds received inputs of both salt and fresh water. Canals permitted an infusion of seawater on the rising tide, while springs, streams and aquifers were sources of freshwater.
Seawater ponds permitted the farming of marine aquatic animals on a sophisticated level. These large ponds required considerably more engineering expertise than other types of ponds. Their main structural feature was a seawall constructed of coral blocks and/or lava rock. Some of these stones are estimated to weigh half a ton. The seawalls were made permeable to permit limited water flow and avoid stagnation. At least 22 species of marine life are known to have flourished in these salt water habitats.
Another feature of the seawater ponds were grates made of timbers bound with ferns. These grates, which were placed in the canal linking the pond with the ocean, permitted only water and small fish to pass freely. In this manner the pond was stocked effortlessly from the sea, while the larger fish were contained. Fish were harvested by nets or by hand.
Traditional aquaculture systems have received little attention from the scientific community thus far. They have tremendous potential for rural development schemes because they are ecologically benign, have low capital costs, require little or no foreign expertise and frequently have higher economic returns than more intensive agricultural systems.