Three overviews on Environment and Aquaculture in the Tropics and Sub-tropics
| ALCOM | GCP/INT/555/SWE |
| Aquaculture for Local Community Development Programme | GCP/RAF/277/BEL |
ALCOM Field Document No. 27
| Three overviews on Environment and Aquaculture in the Tropics and Sub-tropics |
By Birgitta Larsson
Ecologist
(Associate Professional Officer)
ALCOM
Funding Agencies:
SWEDISH INTERNATIONAL DEVELOPMENT AUTHORITY
BELGIAN ADMINISTRATION FOR DEVELOPMENT CO-OPERATION
Executing Agency:
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
Harare, Zimbabwe, December 1994
Aquaculture has both positive and negative effects on the environment. ALCOM (Aquaculture for Local Community Development Programme) seeks to promote the positive effects and mitigate the negative ones.
ALCOM's activities concerning the environment focus on three areas -- water resources management; water-borne diseases; and environmental aspects of aquaculture in the tropics.
This document summarizes and finalizes ALCOM's environmental desk studies. It consists of three separate review papers: “Environmental impact of aquaculture in the tropics and sub-tropics”; “The use of sewage in aquaculture”; and, “Aquaculture and schistosomiasis”.
These studies followed the outcome of ALCOM's Fourth Steering Committee meeting in February 1991, which stated that ALCOM should address environmental aspects of aquaculture “within the concept of water resources management for biological production”.
Previous papers published by ALCOM on the subject were “Aquaculture/inland fisheries and water resources management in southern Africa” (1992) and “Vectors and vector-borne diseases in connection with aquaculture” (1993).
ALCOM is a regional aquaculture and fisheries programme of the FAO (Food and Agriculture Organisation of the United Nations). Based in Harare, Zimbabwe, it covers all the member-countries of SADC (Southern African Development Community): Angola, Botswana, Lesotho, Malawi, Mozambique, Namibia, Swaziland, Tanzania, Zambia and Zimbabwe.
The aim of ALCOM is to assist member-countries improve the living standards of rural populations through the practice of aquaculture. Towards this end, pilot activities are conducted in member-countries to demonstrate new techniques, technologies or methodologies. Successes achieved, ideas derived, lessons learnt, are applied on a wider scale by member governments.
ALCOM is funded by Sweden and Belgium. Its preparatory phase began in 1986, ALCOM, Harare and its first implementation phase in 1990.
Abstract: Environmental aspects of aquaculture in the tropics and subtropics
This paper examines the environmental effects of aquaculture, with emphasis on aquaculture in tropical and subtropical areas. The aquaculture method and intensity determine the type and scale of environmental effects in combination with the physical, chemical, and biological characteristics of the area in question. Extensive aquaculture triggers the least substantial environmental effects and intensive systems the most. Aquaculture can cause ecological change, destroy wetlands habitats and disturb wildlife. Uncontrolled introductions and transfers can change the biodiversity of ecosystems. Human health can be affected and new diseases can be introduced among indigenous fishes. Conflicts can arise over land and water use. On the other hand, integrated aquaculture can increase the efficiency of resource use by converting agricultural byproducts into fish proteins. Also, pond mud can be used as fertilizer on the fields, and the water can be used for irrigation.
Abstract: The use of sewage in aquaculture
Sewage water contains large amounts of nutrients that can be utilized for aquaculture. This practice is thousands of years old in Asia, but has yet to be established in Africa and South America. Public health must always be safeguarded in practices utilizing human or animal waste; this can be done through appropriate culture and handling techniques, and thorough cooking of the food produced.
Abstract: Aquaculture and schistosomiasis
Schistosomiasis, caused by trematode flatworms of the genus Schistosoma, affects 200 million people in 76 countries throughout the tropical and subtropical regions. Approximately 200 000 people die every year from schistosomiasis. It is possible that water-related projects such as irrigation schemes and aquaculture developments increase the prevalence of schistosomiasis by providing the vector snail with favourable habitats, and by increasing people's contact with water. This paper examines all aspects of schistosomiasis, such as life cycle, distribution, prevention and control.
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Section 1: Environmental aspects of aquaculture in the tropics and sub-tropics
Section 2: The use of sewage in aquaculture
Section 3: Aquaculture and schistosomiasis
3. RESOURCE USE
3.1 Land use and space
3.2 Water use and water quality
3.2.1 Water resources
3.2.1.1 The availability of water
3.2.1.2 Losses of water
3.2.1.3 Conservation of water
3.2.2 Water quality
3.2.2.1 Plankton
3.2.2.2 Macrophytes
3.2.2.3 Pollution and pesticides
3.3 Seed
3.4 Feed
3.5 Construction materials
4. OUTPUTS
4.1 Lime and fertilizers
4.2 Bioactive compounds
4.2.1 Therapeutants and antibiotics
4.2.2 Hormones and growth promoters
4.2.3 Antifoulants and chemicals introduced via construction materials
4.2.4 Recommendations on the use of inhibitory compounds in aquaculture
4.3 Wastes
4.3.1 Uneaten food, excreta and mortalities
4.3.2 Bacteria and other microorganisms
4.3.3 Effects of Aquaculture wastes
4.3.4 Treatment
4.4 Escapes
4.5 Introduction and transfers
4.6 Ecological impacts -- interactions with the food web
4.7 Disturbance to Wildlife, and habitat destruction
4.8 Implications on human health
1. Most desired values of some water quality parameters in tropical and sub-tropical aquaculture
2. HUMAN WASTE AS A RESOURCE -- AQUACULTURE USING EXCRETA AND WASTE WATER
3. PUBLIC HEALTH ASPECTS
3.1 Health aspects of excreta and waste water use in aquaculture
3.2 Epidemiological evidence
3.3 Microbiological quality criteria
6. TECHNICAL OPTIONS FOR HEALTH PROTECTION IN AQUACULTURE USING WASTE WATER AND EXCRETA
1 Environmental classification of excreted organisms
2 Tentative microbiological quality criteria for the aquaculture
8. RECOMMENDATION TO MINIMIZE THE HAZARDS OF SCHISTOSOMIASIS RESULTING FROM AQUACULTURE PONDS
9. CASE STUDY - ZIMBABWE
9.1 Intermediate hosts
9.2 Distribution and prevention
1. Schistosoma parasites infecting man in Africa.
2. Endemity of S. haematobium and S. mansoni in the SADC countries.
1a. The life cycle of Schistosomiasis haematobium, also known as urinary bilharzia; the eggs pass out with the urine.
1b. The life cycle of Schistomiasis mansoni, intestinal bilharzia, in which the eggs pass out with the faeces.
2. Snails that act as intermediate hosts for schistosomiasis.
3. Distribution of Schistosoma mansoni and S. intercalatum in Africa.
4. Distribution of Schistosoma haematobium in Africa.
5. The prevalence of S. haematobium among eight to ten year old children in Zimbabwe.
6. The prevalence of S. mansoni among eight to ten year old children in Zimbabwe.