Duckweed Aquaculture

[Vetaqua]

Sascha Iqbal:
Duckweed Aquaculture - Potentials, Possibilities and Limitations for Combined Wastewater Treatment and Animal Feed Production in Developing Countries
SANDEC Report No. 6/99
March 1999

Dept. of Water & Sanitation in Developing Countries, SANDEC
Swiss Federal Institute for Environmental Science & Technology, EAWAG
Ueberlandstrasse 133, CH-8600 Duebendorf, Switzerland

This literature review provides a first overview of the possibilities,
potentials and limits of duckweed aquaculture and its combined
use in wastewater treatment and animal feed production in low
and middle-income countries. It is somewhat limited as critical
literature on duckweed field use is scarce and difficult to obtain
(e.g. unpublished internal documents). According to NGOs and
commercial suppliers, the duckweed projects seem very positive
and promising, and the practical problems encountered with
their application rarely mentioned.
Nevertheless, extensive scientific literature is available on the taxonomy,
physiology and ecology of duckweed. The comprehensive
monographic study by Landolt (1986) and Landolt and
Kandeler (1987) lists over 3400 references. This can be attributed
to the fact that duckweed is regarded by botanists and
plant physiologists the same way as E. coli is viewed by
microbiologists and biochemists, namely a model organism for
physiological, biochemical and metabolic studies, easy to handle
and cultivate under laboratory conditions. This monographic
study is of key importance for further research on the use of
duckweed. Other references of major importance are the literature
review by Gijzen and Khondker (1997) and the DWRP reports
(DWRP 1996, 1997a and 1997b) which give a comprehensive
overview of the “state of the art” of duckweed-based
treatment/production systems and duckweed related research.
These references were a major source of information for the
present document.
The current review focuses on the combined use of duckweed
in wastewater treatment and animal feed production in economically
less developed countries. Despite the fact that most of the
available literature originates from industrialised countries and
often describes either the wastewater treatment or the feed production
aspect of duckweed, but its dual use is rarely discussed.

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Another Full Manual:

William K. Jourmey, Paul Skillicom and William Spira
DUCWKEED AQUACULTURE - A NEW AQUATIC FARMING SYSTEM FOR DEVELOPING COUNTRIES
THE WORLD BANK EMENA TECHNICAL DEPARTMENT - AGRICULTURE DIVISION

Summary: This booklet introduces a group of tiny aquatic plants commonly known as "duckweeds" as a promising new commercial aquaculture crop. Duckweed species are ubiquitous, hardy, and grow rapidly if their needs are met through sound crop management. Aquaculture systems are many times more productive than terrestrial agriculture and have the potential to increase protein production at rates similar to increases of terrestrial carbohydrate crops realized during the Green Revolution. This paper summarizes current knowledge, gained from practical experience from the beginning of 1989 to mid-1991 in an experimental program in Mirzapur, Bangladesh, where duckweed cultivation was established and fresh duckweed fed to carp and tilapia. Like most aquatic plants, duckweed species have a high water content, but their solid fraction has about the same quantity and quality of protein as soybean meal. Fresh duckweed plants appear to be a complete nutritional package for carp and tilapia. Duckweed-fed fish production does not depend on mechanical aeration and appears to be significantly more productive and easier to manage than traditional pond fish culture processes. The economics of duckweed farming and duckweed-fed fish production and institutional factors that are likely to affect its wide-spread adoption as a commercial crop are discussed. Duckweeds are also used for stripping nutrients from wastewater.

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A good Online-Article extra:

R A Leng, J H Stambolie and R Bell
Duckweed - a potential high-protein feed resource for domestic animals and fish
Livestock Research for Rural Development
Volume 7, Number 1, October 1995

Summary

Duckweeds have received research attention because of their great potential to remove mineral contaminants from waste waters emanating from sewage works, intensive animal industries or from intensive irrigated crop production. Duckweeds need to be managed, protected from wind, maintained at an optimum density by judicious and regular harvesting and fertilised to balance nutrient concentrations in water to obtain optimal growth rates. When effectively managed in this way duckweeds yield 10-30 ton DM/ha/year containing up to 43% crude protein, 5% lipids and a highly digestible dry matter.

Duckweeds have been fed to animals and fish to complement diets, largely to provide a protein of high biological value. Fish production can be stimulated by feeding duckweed to the extent that yields can be increased from a few hundred kilograms per hectare/year to 10 tonnes/ha/year.
Mature poultry can utilise duckweed as a substitute for vegetable protein in cereal grain based diets whereas very young chickens suffered a small weight gain reduction by such substitution. Pigs can use duckweed as a protein/energy source with slightly less efficiency than soyabean meal.
Little work has been done on duckweed meals as supplements to forages given to ruminants, but there appears to be considerable scope for its use as a mineral (particularly P) and N source. The protein of duckweeds requires treatment to protect it from microbial degradation in the rumen in order to provide protein directly to the animal.
The combination of crop residues and fresh duckweeds in a diet for ruminants appears to provide a balance of nutrients capable of optimising rumen microbial fermentative capacity. These diets can, therefore, be potentially exploited in cattle, sheep and goat production systems particularly by small farmers in tropical developing countries.

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Another interesting Book:

Hasan, M.R.; Chakrabarti, R.
Use of algae and aquatic macrophytes as feed in small-scale aquaculture: a review.
FAO Fisheries and Aquaculture Technical Paper. No. 531. Rome, FAO. 2009. 123p.


This technical paper presents a global review on the use of aquatic macrophytes as feed for farmed fish, with particular reference to their current and potential use by small-scale farmers. The review is organized under four major divisions of aquatic macrophytes: algae, floating macrophytes, submerged macrophytes and emergent macrophytes. Under floating macrophytes, Azolla, duckweeds and water hyacinths are discussed separately; the remaining floating macrophytes are grouped together and are reviewed as ‘other floating macrophytes’. The review covers aspects concerned with the production and/or cultivation techniques and use of the macrophytes in their fresh and/or processed state as feed for farmed fish. Efficiency of feeding is evaluated by presenting data on growth, food conversion and digestibility of target fish species. Results of laboratory and field trials and on-farm utilization of macrophytes by farmed fish species are presented. The paper provides information on the different processing methods employed (including composting and fermentation) and results obtained to date with different species throughout the world with particular reference to Asia. Finally, it gives information on the proximate and chemical composition of most commonly occurring macrophytes, their classification and their geographical distribution and environmental requirements.

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Some further Informations for probable Pest Control related to this topic:

Insects and Other Arthropods That Feed on Aquatic and Wetland Plants.
USDA/ARS Technical Bulletin 1870 October 2002

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