aquaculture

Water Hyacinth (Eichhornia crassipes) infestations around the world have caused environmental chaos and changed natural and human communities beyond recognition. Water Hyacinth has found uses, but in general, has proven to be a highly invasive species with few cost-effective management solutions.

Global Education reports on the use of biological control of water hyacinth in Papua New Guinea, noting that within ten years of introduction into the Sepik River, water hyacinth had invaded to the extent that some village people died – snake bite victims could not get to hospital in time, other people starved because they could not get to their gardens or to markets, and contaminated water caused diseases and provided breeding grounds for malaria carrying mosquitoes. Mechanical clearing and herbicides proved to be uneconomic and ineffective.

Australian scientists from the CSIRO Entomology found that the South American Chevroned Water Hyacinth Weevil (Neochetina bruchi) fed on the leaves of water hyacinths, while their larvae tunnel into the leaf stalk and crown, destroying the growing points. The plants rot and die quickly in the warm temperatures favoured by the hyacinths. Once established, the impact of the weevils is rapid, visible and long lasting.

According to Science Daily, the CSIRO scientists released some 450,000 weevils (Neochetina bruchi and Neochetina eichhorniae) in the Sepik River wetlands. Hyacinth infestations were reduced from 27 square kilometres to just seven in five years.

In the Status of biodiversity in Papua New Guinea, by Miller, S.; Hyslop, E.; Kula, G., and Burrows, I., reported that another aquatic weed, Salvinia molesta is now widespread in Papua New Guinea. First recorded in 1977 at Wau, and on the Sepik River in 1971-72; by 1979, salvinia covered 80 square kilometres and the physical impact of the weed was reflected in the decline in fish catches, crocodile hunting, and sago gathering, and also in the disruption to the lives of Sepik villagers. People in a number of villages were unable to reach markets to sell produce and children were prevented from attending school. Biological control using the South American weevil Cyrtobagous salviniae was extremely successful. By June 1985, self-sustaining populations of the weevil had destroyed an estimated two million tonnes of weed which had covered 250 square kilometres. The local people have now resumed their former lifestyles.

The techniques learned in Papua New Guinea are now being applied in other countries. The ABC report on the developments in Lake Victoria, where the use of the weevils has again begun to have an impact on the infestation. Dr Mic Julien, the CSIRO biologist who had lead the project the Sepik River has demonstrated to African authorities what can be achieved – bio-control offers a long-term, sustainable answer.

Blue Genes – Sharing and Conserving the World’s Aquatic Biodiversity is a free, online book by David Greer and Brian Harvey.

Here’s the summary:

The advance of genetic sciences has led to a “blue revolution” in the way we use aquatic biodiversity.

By 2020, the world will be eating almost as much farmed as world fish, marine bacteria could yield the cure for cancer, and deep-sea bacteria may be exploited to consume oil spills. Science is moving ahead at a staggering speed, and the demand for genetic resources is growing rapidly – yes governance and policy lag far behind.

This groundbreaking work is the first to look at the issues of ownership, governance, and trade in aquatic resources. Blue Genes describes the growing demand for aquatic genetic resources and the desperate need to fill the policy vacuum for the management and conservation of aquatic biodiversity as a foundation for rules governing access to and use of aquatic genetic resources. Special attention is paid to the rights of indigenous and local communities providing access to those resources and their role in managing and conserving aquatic biodiversity.

The book concludes with policy recommendations specifically tailored to aquatic resources and uses six case studies from four continents to illustrate key issues.

The South African Institute for Aquatic Biodiversity is a centre for the study of fishes. Their research programmes are designed to answer questions on biodiversity and marine science through study of rare species including the endangered population of coelacanths.

Since a living specimen of the coelacanth was first found in 1938, the ‘fossil fish’ previously known only from fossil records, has captured the imagination of the public and scientists alike. By probing the secrets of this beautiful and enigmatic fish, the Coelacanth Programme could become a flagship programme for marine biodiversity in South Africa and internationally.

Sena S. De Silva, Rohana P. Subasinghe, Devin M. Bartley, and Alan Lowther; from the Food and Agriculture Organisation of the United Nations (FAO) authored a review (FAO Fisheries Technical Paper. No. 453. Rome, FAO. 2004. 65p.) on tilapia as an alien aquatic species, available online.

The abstract:

Tilapias are not native to Asia but have been a significant component of inland fisheries and aquaculture in the region for over half a century. They have been introduced into over 90 countries worldwide, with a global distribution second only to common carp. The contribution of tilapias to global aquaculture production has increased over the past three decades with production in 2002 exceeding 1.5 million tonnes with an estimated value of US$1.8 billion. The average annual growth rate in aquaculture and capture fisheries production of tilapias from 1970 to 2002 has been 13.2 percent and 3.5 percent, respectively. In the present context of development, success of a species is determined not only by its contribution to production per se, but also by its social, cultural, economic and environmental impacts. Although tilapia has been associated with adverse environmental impacts, detailed analysis of the literature suggested that other factors, such as overfishing, environmental degradation from land-based activities, and changes in hydrological regime have probably been more responsible for adverse impacts. It is clear that numerous factors working together can impact biodiversity. It is also clear that tilapias, as a group of alien species, have made a significant contribution to food production, poverty alleviation and livelihoods support in Asia and the Pacific. In spite of the wide-scale introduction into Asian waters, there is scant explicit evidence to indicate that tilapias have been overly destructive environmentally.

Water Hyacinth (Eichhornia crassipes) usually floats free in large masses but may be rooted in the mud. The plants may range from a few inches to as much as 90cm (3 feet) in height. They have slender rootstocks with rosettes of leaves and dark, fibrous, branching roots dangling beneath the plant. Flowers may be blue, violet, or white and are usually quite showy.

In many regions Water Hyacinth is regarded as being amongst the worst of aquatic weeds. However, there is a continued theme from some researchers that there is significant benefit to be obtained from seeing the Hyacinth a resource rather than a rogue.

In an abstract from 1985, Ricardo B. Jacquez and Walter H. Zachritz II report on Combining nutrient removal with protein synthesis using a water hyacinth-freshwater prawn polyculture wastewater treatment system. They report overall performance of the polyculture system for the removal of total COD, TSS, total coliforms (MPN), and turbidity (NTU) indicated removals of 58, 98, 99.9, and 94 percent, respectively. Other parameters for the two stage system were monitored including temperature, Ortho-P, biomass, productivity, alkalinity, pH, and specific conductance.

F. Shoeb and H. J. Singh (2000) have published Kinetic Studies of Biogas Evolved from Water Hyacinth. The paper deals with the kinetics of gas produced from Water Hyacinth. The study was done in a batch fed digester. Attempts have been made to reach an optimum condition for the production of maximum amount of gas by the addition of lower volatile fatty acids, cow dung and inoculums etc. The conclusions that were drawn from the study is that biogas plants can be run even on the cold winter nights by using certain additives. After digestion, Water Hyacinth inoculums can be used as good manure for soil fertility. They are free from harmful chemicals – a boon for sustainable agriculture practices.

permaculture@lists.ibiblio.org have captured information about Uses for water hyacinth – Las Gaviotas project from August 2002. The information lists two links which are now invalid. Sad, because it would be interesting to see how the information had updated over time. This focus of this research has taken a rather different approach:

Oyster Mushrooms:
Scientific research initiated by Margaret Tagwira for ZERI Foundation demonstrated that dried water hyacinth is the best substrate for farming mushrooms. This program directed by Prof. S. T. Chang, an authority on the matter, confirmed that the water hyacinth is a blessing in disguise. Sociological studies confirmed that nearly all African cultures had mushrooms as a part of their diet. The spent substrate after fungi harvesting is rich in protein from the mycelia of the mushrooms and are excellent feed for earthworms, which convert it all into humus and can be fed to chickens, ducks and pigs.

After only 30 days, the dried substrate from water hyacinth produced a variety of mushrooms. Once harvested, it did not take more than ten days to harvest a second and even a third flush. One hundred kilograms of dried water hyacinth generates more than 100 kilograms of mushrooms. The water hyacinth outperforms traditional substrate materials such as sawdust. In addition, since the substrate of water hyacinth is rich in minerals and nutrients, the oyster and straw mushrooms cultivated ended up enriched with potassium, magnesium, iodine and calcium, along with numerous other components that are critical to a healthy food diet. Much of what was lost in the form of washed away topsoil can be recovered in the mushroom. The water hyacinth can also recover harmful metals such as cadmium and lead and store them in their roots if these metals are found in the rivers or lakes.

Lake Victoria is shared by Kenya, Tanzania and Uganda. It was named after the Queen of England and is the world’s largest tropical lake and the second largest freshwater lake. Since 1858, when the British explorer John Speke ‘discovered’ Lake Victoria, there has been a great deal of research undertaken on the lake, its inhabitants, the ecosystems and surrounding environments.

Nancy Chege, of the Worldwatch Institute, writes in www.cichlid-forum.com, Lake Victoria: a sick giant.

The ecological health of Lake Victoria has been affected profoundly as a result of a rapidly growing population, clearance of natural vegetation along the shores, a booming fish-export industry, the disappearance of several fish species native to the lake, prolific growth of algae, and dumping of untreated effluent by several industries. Much of the damage is vast and irreversible. Traditional lifestyles of lakeshore communities have been disrupted and are crumbling. There is a consensus among scientists that if an accelerated push to save the lake is not made soon, this much-needed body of water will cease to sustain life.

Lake Victoria represents a large scale issue to be resolved by governmental and business interests. Some cross-border responsibility is called for, rather than the pursuit of money with scant consideration for the health and welfare of the local communities whose livestyles and health depend on the health of the lake According to a Greenpeace report, “In the 1960s, for instance, the Nile perch was introduced into Lake Victoria in Africa and, within a decade, the local population of over 400 different smaller fish species declined from 80% to 2% of the lake’s total fish stocks. Probably 50% of the native species disappeared from Lake Victoria because they were not able to cope with the new invader exhibiting its insatiable hunger.”

At its fifth session, the Sub-Committee for the Development and Management of the Fisheries of Lake Victoria reviewed a variety of action programmes and made recommendations to Member Governments on their implementation. Programmes reviewed were concerned with fisheries development, management measures, protection of the environment and prevention of pollution, the water hyacinth, development of aquaculture, fish processing and marketing and technical, scientific and socio-economic issues involved in research policy. It was agreed by members that the concept of the International Code of Conduct for Responsible Fishing was applicable to Lake Victoria. The sub-committee agreed on procedures for the establishment of the Lake Victoria Fisheries Organization. The report is available online.

Chenge, again reports:

A more recent threat to the lake is the water hyacinth. With the deceptive appearance of a lush, green carpet, the hyacinth is a merciless, free-floating weed, reproducing rapidly and covering any uncovered territory. First noticed in 1989, the weed has already spread like wildfire, and has covered areas in all three countries. It forms a dense mat, blocking sunlight for organisms below, depleting the low concentrations of oxygen and trapping fishing boats and nets of all sizes. The hyacinth is an ideal habitat for snails that cause bilharzia and for snakes. Scientists are desperately trying to control the weed: their most promising approach involves harvesting the hyacinth and using it either for compost or for biogas production.

Richard O. Abila, Researcher, Kenya Marine and Fisheries Research Institute, Kisumu, Kenya; writes in Fish Trade and Food Security: Are They Reconcilable in Lake Victoria?:

The Lake Victoria fishery has come under increasing pressure in the last two decades. Fish production peaked in the early 1990s and currently catches of most species are showing downward trends. Despite this, there is greater demand for fish of Lake Victoria, chiefly Nile perch (Lates niloticus) and ‘dagaa’ (Rastrineobola argentea), in the export market and for fishmeal respectively, as well as for domestic consumption. The present situation is the consequence of the tremendous commercial transformation that the fishery of Lake Victoria has undergone in those 20 years. From a local-based subsistence fishery before 1980, it is presently dominated by fish processing factories funded from international sources, which aim at enhancing fish exports from East Africa to the developed world, so as to earn more foreign exchange. This takes place against a backdrop of a protein-starved local community whose livelihood depends on the lake. In the past, international trade on fisheries was taken for granted as the means to tackle poverty and food insecurity for fisheries-dependent communities. That idea has, however, been challenged in the last few years as researches look critically at the benefits of global fish trade vis-à-vis the costs, particularly in relation to food insecurity and environmental implications. This report is a further contribution to this debate. It tries to establish a link between the increased liberalization of trade in the fisheries of Lake Victoria and the food insecurity indicators. The paper is based on primary and secondary data collected at various times, published and unpublished documents as well as the author’s own observations over several years working as a researcher on socio-economic aspects of the Lake Victoria fishery. Because of the large investment already made in industrial fish processing, it would be in order to allow some amount of exports to continue. However, the quantities of exportable fish must be limited to ensure sustainable fisheries and reconciliation with the food security needs. Recommendations are made in four broad directions to make Lake Victoria fisheries more relevant to the food security needs of the local population. They include specific policy interventions, interventions in fisheries management, steps to enhance fish supply and refocusing the fish marketing strategies. There is also need for more incisive studies on the fish industry and at household level to understand in greater depth how the various factors raised in this study relate to each other and the magnitude of their contribution to food insecurity.