.
Geology and hydrology The Buada Lagoon, which is found in the southwest of the plateau that spreads over most of the central part of the island of Nauru, lies in the middle of a swampy depression of 12 hectares. This
karstic bowl, Oval in shape, with a length of roughly 280 m along a north-south axis and a width of about 140 m, and lying some 1,300 m from the seashore, the Buada Lagoon is shallow, with a depth of one or two metres on average, reaching five metres at its deepest, the low-water level can sink as far down as five metres below sea level. The undergrowth is mainly made up of: There are parasitic plants like
Cassytha filiformis, or
Psilotum nudum. Also grown are
ylang-ylang,
Cassia grandis,
Crotalaria spectabilis,
Samanea saman,
seagrape and, for ornamentation, some
Asteraceae such as
Ageratum conyzoides and
Synedrella nodiflora. Thus, three species of
mosquito,
Culex quinquefasciatus,
Culex sitiens and
Aedes aegypti, proliferate in the monsoon season from November to February near expanses of stagnant freshwater like household rainwater cisterns, used tires, wells and, of course, the Buada Lagoon, albeit only slightly more seriously than towards the seashore.
Birds Birds, particularly seabirds, are Nauru's most visible animals, and some stop there in great numbers during
their migration or for nesting. In certain years,
Nauruans traditionally practised
pisciculture by catching milkfish in the island's inshore waters (by some definitions, the actual lagoon, just behind the offshore coral reefs) and releasing them into the Buada Lagoon and another such body of water at
Anabar. Unfortunately, the tilapias multiplied to such an extent that they presented some serious competition to the milkfish being raised in the lagoon, with no milkfish ever reaching a size suitable for harvest, that being some long. This led many fish farmers to give up the trade, as the tilapias themselves were not very good to eat. To set this ecological blunder right, a number of attempts were made, some meeting with no success, and others even worsening an already bad situation. So the
Food and Agriculture Organization of the
United Nations (FAO), at Nauru's request, from 1979 and 1980 put in place a programme to reduce the tilapia population. This programme entailed spreading
rotenone on the lake's surface; this is a highly toxic
molecule, particularly to fish, and dangerous to humans, but also biodegradable. The lake was thus temporarily poisoned. In 1991, the FAO's "South Pacific Aquaculture Development Project" (SPADP) showed that it was possible that the milkfish and the tilapia could coexist in fish farming. The FAO thus introduced in 1998
Nile tilapias into the Buada Lagoon, an experiment much like one carried out in
Fiji that had been able to show the Nile species possessed qualities that better appealed to local people's tastes. This meant that pisciculture might be revived in Nauru. At the same time, a
Taiwanese project also sought to revive fish farming by using intensive methods of raising fish, but these were nevertheless both given up for want of funds. The failure of these attempts to get the fish farming industry running again then led to the establishment in 2001 of a semi-intensive aquaculture programme, also Taiwanese, which involved building concrete basins . These were equipped with oxygenators, nets and specially adapted feeding. The idea was to allow fish farmers to raise milkfish using seawater, and without having to share the water with tilapias. == Human presence ==