The technique of Bamburi is to excavate down to 30 cm to 50 cm above the groundwater level. As a result small lakes, ponds and swamps were excavated and habitats for fish, birds and reptiles created. Wherever possible, water bodies and swamps were inter-connected by channels for the free movement of aquatic organisms. In a larger lake (wildlife sanctuary) hippopotami were introduced to keep the water-body healthy and prevent it from silting.
The Bamburi Integrated Aquaculture system constitutes of the fish farm, crocodile unit, and a bio-filtration component. The rejected fish are used as part of food items for the crocodiles. In the early days of the aquaculture system, the hippopotamus pond was an important part of the fish farm, as the nutrients released into the water by the hippos encouraged the productivity of the water system, and therefore the food organism for the tilapia fish. However, over the years nutrients have accumulated in the water system, and now the challenge is to reduce the nutrient load in the water, which is being achieved by recycling and channelling the water around the reclaimed land, which also supports the planted trees. The system is run biologically, with no pesticides, artificial fertilizer or chemotherapy for fish, crocodiles and plants being applied. This is to avoid upsetting the delicate balance in the system.
In the very beginning of the quarry rehabilitation project, that is in the 1980, Fish farming was a project to generate income, as there was plenty of water available, as well as machinery to excavate ponds into the quarry floor. René Haller had originally intended to use the quarry ponds for fish culture but this proved impractical due to their rapid reproduction that resulted in the rapid over population of the ponds, moreover there was no drainage in the ponds. Today the aquaculture unit serves as a showcase of aquaculture management. The species chosen for cultivation were the local Tilapia, a favoured food fish growing well in warm, saline water. The name ‘Tilapia’ originally derives from the Bushman name for fish ‘click’-apia. Today other fish like the Catfish and guppies have been added.
Catfish are a fascinating and diverse group of fish which have become hugely popular as aquarium fish. They range from the tiny Otocinclus to giants like the Red-Tailed catfish. Catfish are also scaleless, and some are protected instead by 'armour' consisting of bony plates. The variety of size and form of catfish means there is a species to suit almost any aquarium setup.
Catfish (order Siluriformes) are a diverse group of fish. Named for their prominent "barbels", which give the image of cat-like whiskers, they are found in freshwater environments of all kinds, with species on every continent except Antarctica.
Guppies were introduced in our Ecosystems at the onset of Fish farming experiments. Over time they continued playing important roles in the ecosystem and formed important part of the ecosystem development as integral part of the ecosystem food web.
The guppy,also known as guppie (Poecilia reticulata) is one of the most popular freshwater aquarium fish species in the world. It is a small member of the Poecilidae family (females 3 centimetres long, males 2 centimetres long) and like all other members of the family, is live-bearing. It prefers a hard water and can withstand levels of salinity up to 150% sea water. Its most famous characteristic is its propensity for breeding.
Nile Crocodiles in Haller Park have in the past been referred to as dustbins. This was simply based on the fact that they ate almost any piece of bone and flesh that they came across in their enclosures.
Our original parent stock comprised of six (6) females, and one (1) male which came from the Tana River and Lake Turkana as hatchlings in 1975. In Haller Park the crocodiles are an important part of the integrated aquaculture system, digesting bones and feeding on waste. They excrete high levels of dissolved phosphate, a nutrient which is important for plant growth and giving their water a green colour from the plank algae which flourishes due to high nutrient levels. These phosphates supplement the nitrogen rich effluents from the fish farm, putting the correct balance of nutrients into the system for successful plant growth.
Today population of 75 to 80 crocodiles remains to maintain a purely ecological role. The crocodiles are fed only once a week on meat or fish.
Above the crocodile enclosure are hundreds of weaver bird nests. These birds seek the protection of the crocodiles underneath their nesting trees.
Roles of plants in bio-filter systems:
- Filtration (root &/or stems may act as mechanical filter)
- Increase sedimentation (by reducing flow rates between stems/roots)
- Provide substrate for bacteria - increase active surface for bacteria to settle & feed.
- Some swamp plants release of oxygen into the root system, thereby increasing active area for aerobic bacteria.
- Uptake of mineralized nutrients into biomass, which can be harvested & removed from the system