Report 4 (of 5): Weed to the Rescue - Madagascar

Introduction

Until recently, families living on the coast of Madagascar depended on the plentiful supplies of fish to provide income but unregulated fishing over the last ten years has severely depleted stocks. Many of the fishing villagers are being forced to find an additional source of income. The European Commission has been working with a French multinational company and the local fishing community to develop seaweed farms which could provide an alternative to fishing.

As well as being used as one of the main ingredients for toothpaste, seaweed is becoming increasingly popular as a delicacy. The global demand for seaweed is growing at an annual rate of 6 per cent and there is room in the market for new producers.

Cultivation of Seaweed

The successful cultivation of seaweed is due to the farmer knowing the plants and the local environment, and caring for the welfare of the plants by paying attention to detail. During the planting, maintenance, harvesting and culling of the seaweed, if a mistake is made the entire process can fail.

Site Survey

A site survey needs to be conducted to determine which specific sites have the greatest possibility of success. There are many parameters to a good site with the primary concerns being water flow, temperature and salinity. Light is important, but it is assumed not to be limiting.

An ideal site will be close to home within protected waters, i.e. no pounding waves, and will be in an area not being used for any other purpose, such as fishing or boat mooring. Once such a site has been identified, the environmental parameters need to be measured.

Seaweed should never be planted on a reef flat without first observing the full range of tides. Seaweed can grow very well in muddy water, for example, off mangrove forests but certain siltation can cause decreased growth.

In order to conduct a proper site survey, the parameters should be recorded. The following tools are required to do this properly: refractometer; accurate alcohol thermometer which covers the ranges 15 to 40°C; a copy of a nautical chart for the area or a sketch of the area; a tide book; a notebook and pen; a bottle; a 5 metre string and a watch with a second hand; and a basic knowledge of identifying seaweeds and seagrasses.

Environmental Parameters

Temperature: two readings need to be taken - one in the early morning and one in the late afternoon to provide the daily lows and daily highs of the water temperature. Highs and lows must fall within the range of 23 to 32°C in order for the site to be considered as a prospective site.

Salinity: all sites with a salinity outside 23 to 38 parts per thousand should be excluded.

Water Motion: locations with high tidal water motion are the most attractive sites. To monitor the water motion due to tidal activity, readings are taken at exactly the mid-time between high and low tide when the tidal current is assumed to have the highest speed. A bottle is filled with seawater so that it barely floats and then it is capped. A five metre string is tied to the bottle and the number of seconds that it takes to travel with the current for the five metre distance is recorded. This should be done five times to find the average time. For water flow, sites where the time for the bottle to travel the five metres exceeds 25 seconds at maximum tidal flow should be excluded.

Test Plot

Having surveyed sites and excluded those sites which had at least one environmental parameter outside the specified range, a test plot should be carried out at the remaining sites.

A standard test plot consists of one five metre line with propagules (individual plants) attached every 20 centimetres. It is designed to see if the seaweed will grow at a particular location and will also give insight into herbivore and pest weed activity. Propagules should be healthy and weigh about 100 grams, be strong, well branched and free from necrotic tissue and algae.

Off Bottom Test Plot

In a reef flat location, an off bottom test plot is created by placing two wooden stakes five metres apart, with only about 40 centimetres showing above the water (figure 1). Plastic straw is tied to a six metre twisted nylon or polyethylene line (5mm diameter) at 20 centimetre intervals and then the propagules are attached to the nylon line using the plastic straw. The nylon line is then attached to the wooden stakes.

Floating System Test Plot

For deep water areas, a floating system is used (figure 2). Propagules are attached to a six metre nylon line as for a reef flat location. Two anchor lines and two floats made of either plastic bottles or styrofoam pieces are attached to the test line with the anchor to surface float angle at about 45° at high tide. Two rice sacks filled with sands or stones weighing up to about 10 kilogrammes are used as anchors. Two small stones (300 grams) with 30 centimetres of nylon tied to them are attached to the anchor line.

Growth of the Propagules

The line with the propagules attached should be weighed and then the plants on the test line should be allowed to grow for 21 days. During this time, the plot should be maintained twice a week by cleaning any attached debris, retying loose lines and bottles and replacing loose stakes. Missing propagules should not be replaced.

After 21 days, the line should be reweighed and the number of propagules left should be counted. If there is little growth, then the site is obviously not going to provide a satisfactory growing place for seaweed although in a different season it may be fine. The presence of herbivore activity and pest weeds also indicates if the test plot is a good growth location.

After a few years experience, farmers learn what locations have superior growth conditions for certain times of the year and test plots become unnecessary.

Farming of Seaweed

Once a plot has been found, the propagules should be allowed to grow for between 30 and 40 days. Maintenance of the seaweed farm is a top priority and needs to be carried out twice a week. The seaweed lines needs to be checked for green algae which may otherwise choke the plants; if propagules are lost they need to be replaced; if plants are dead or dying they need to be harvested and young, clean and strong propagules need to be replanted; lines, stakes and anchors need to be retied and replaced where necessary.

Income Generation in Beravy, Madagascar

At Beravy in Madagascar, the villagers have readily taken to this new source of income and there are now about 150 families involved in the cultivation of seaweed. Seaweed farming does not just create jobs for those living on the coast. A local operator in Madagascar, Biomad, employs 15 part time workers to sift and sieve the dried up bundles. A further 13 permanent staff, package the seaweed and administer the operation.
 

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Intermediate Technology would like to thank Erick Ingvald Ask for providing the original handbook and drawings on Seaweed Cultivation.

TVE/ Practical Action gratefully acknowledge support for the HANDS ON programmes from the UK's Department for International Development (DFID), the European Commission (EC), the UN Foundation and UNDP/The Equator Initiative in collaboration with the Government of Canada, IDRC, IUCN, BrasilConnects and the Nature Conservancy.