aquaculture

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.

APFIC have published a number of reports available as free downloads about the rehabilitation of fisheries and aquaculture in coastal communities in those countries affected by the 1994 tsunami.

Strategic framework – Rehabilitation of fisheries and aquaculture in tsunami affected countries represents a regional strategic framework that has been developed in support of recovery and rehabilitation efforts following the earthquake and subsequent tsunami waves that originated off the west coast of northern Sumatra on the 26 December 2004 and that caused extensive damage to coastal communities in the region.

The framework presented consists of a vision for the rehabilitation of the fishery and aquaculture sectors which reflects an “ideal state” towards which all strategies and activities contribute and which avoids the mistakes of the past.

In response to the disaster, a consortium (CONSRN) of key regional agencies was formed with the objective of supporting coordination and harmonization of rehabilitation efforts in fisheries and aquaculture. In particular, it was agreed that activities were to focus on collating and disseminating information, carrying out assessments and supporting partners and governments to build a common vision for post-tsunami rehabilitation of the sector.

Other documents available as free downloads include: the report of the FAO/MOAC Joint tsunami assessment mission – Thailand. This is a report of a joint FAO/Ministry of Agriculture and Cooperatives (MOAC) detailed technical damage and needs assessment mission in the fisheries and agriculture sectors.

This is the final report of the Regional Workshop on Rehabilitation of Fisheries and Aquaculture in Coastal Communities of Tsunami Affected Countries in Asia held in Bangkok, Thailand from 28 February to 1 March 2005 is also available as a free download. Major topics discussed were: introduction to workshop and regional strategic framework; country priorities for rehabilitation; the rehabilitation vision and guiding principles; rehabilitation strategies; aligning donors/agencies/ countries to strategies and the workshop recommendations.

The FAO have published a report Preliminary Stock Assessment for the Shallow Water Shrimp Trawl Fishery of Tanzania based on catch and effort data for 1988. The report focuses on trawl fishing rather than farming, but it gives valuable indications in terms of times and conditions.

Issues related to the establishment of prawn farms in Tanzania, with an example from the Rufiji delta are available in this report published by the Mangrove Management Project, Forestry and Beekeeping Division of the Institute of Resource Assessment, University of Dar es Salaam.

A giant prawn farm to expropriate one third of the mangroves of the Rufiji Delta has recently been proposed by a private developer, the East African Fishing Company Limited, a subsidiary of TANNOL Holdings Ltd. Prawn farms have over the past 5 – 6 years been proposed for various locations along the Tanzanian coast, but none have so far been established.

This has generally been due to shortfalls in addressing social and environmental issues; issues often raised in Environmental Impact Assessments. The decisions not to approve projects have mostly been taken by funding or credit agencies and have rested upon experiences from similar projects in other countries where prawn farming has been practised in Asia and America. Both the positive and negative impacts of establishing large scale prawn farming are well documented in global literature.

The FOA have a published report (1997) as part of the support to the special plan for prawn and shrimp farming about Site Selection Towards Sustainable Shrimp Aquaculture in Myanmar. The executive summary notes: Shrimp culture in Myanmar is as yet little developed. Out of an estimated potential area of 48,000 ha, only 16,000 are used for traditional and extensive culture. A mere 80 ha use semi-intensive culture. Rakhine State predominates with 97% of the culture area.

Shrimp culture is expected to expand rapidly with the introduction of semi-intensive shrimp farming technology transferred from Indonesia. To avoid serious environmental and shrimp disease problems which have plagued other ASEAN shrimp producers, environmental impact assessment and best management practices (BMP) should be introduced.

The outstanding issues generated by semi-intensive shrimp farm development are:
1. Destruction of mangrove forest ecosystem
2. Deterioration in water quality
3. Land allocation
4. Economic losses through disease and poor management.

Sustainable shrimp aquaculture rests on a healthy mangrove ecosystem. It should not be forgotten that the mangrove forest is the nursery ground for cultured shrimp species, whose genetic diversity forms the basis of the shrimp aquaculture industry.

Uncontrolled destruction of the mangrove ecosystem will lead to reduced breeding stocks of major cultured species. Not only will genetic diversity decline, but spawners and brood stock will become increasingly difficult to catch.

Shrimp farming depends upon high water quality. Mangroves and the biota associated with them are a natural biofilter, removing excess nutrients and sediments discharged by shrimp farms. Mangroves protect shorelines from erosion and are very effective storm breaks.

A report published by the United Nations Development Programme (Aquaculture extension through trickle-down: Bangladesh) claims that Bangladesh is considered one of the most suitable countries in the world for aquaculture, because of its favourable agroclimatic conditions. Development of aquaculture has generated considerable employment through the production and marketing of fish and fish seed.

The revolution in water/aquaculture-based food production systems (the so-called “blue revolution”) in Bangladesh has achieved a 50 percent increase in aquaculture production, mainly as a result of new semi-intensive technology using locally available feed ingredients and other inputs. The Food and Agriculture Organization of the United Nations (FAO) has been helping the government to develop and test this technology in different agroclimatic regions of the country. Householders have at least doubled their income from raising carp and other fish in traditional backyard pools.

According to a report published by Dr. M.A. Mazid, Director, Fisheries Research Institute, Mymensingh-2201, Bangladesh and Mr. M.G.M. Alam, Research Student, Tsukuba University, Japan:

In the agro-based economy of Bangladesh, fisheries play an important role in nutrition, employment and foreign exchange earning, contributing 4% to GDP, 10% to export earning, 73% to animal protein intake, in addition to providing 1.4 m people full time and 11 m part time employment. The vast water resources covering 4.3 m ha of inland water and 480 km coast line with sub-tropical climate, and suitable soil and water conditions offer a very high potential for fisheries and aquaculture development. Out of total fish production of 1.08 m tons, inland open water capture fisheries generate 51%, inland fresh and brackish water aquaculture 25% and marine capture 24%.

Production from inland open water capture fisheries is being depleted due to over-exploitation and habitat degradation. However, aquaculture production both from fresh water and brackish water which mostly follows traditional and improved traditional practices has been steadily increasing. Semi-intensive shrimp farming in a limited scale is a recent development where production of 3-5 ton/ha is being obtained. Production from improved traditional practices which comprises over 95% of the total shrimp farming is as low as 300-500 kg/ha. Aquaculture technologies so far developed and practiced in Bangladesh include polyculture of carps, integrated aquaculture, culture of tilapia and silver barb in seasonal water bodies, breeding and culture of various catfishes, culture of fish in pens, brood stock improvement and nursery management etc. These are very low input environment friendly sustainable technologies being able to produce 2-6 ton/ha or more depending on the management and culture practices with assurance of good quality produce.