Artificial Reefs

In small island states, interest in the development of artificial reefs has grown steadily over the past two decades. Furthermore, this concept has been proven to be a promising technique to increase and enhance fishing. Therefore, it fits well into programmes where development and management of marine food resources is concerned.

The creation of artificial reefs is not a recent activity since in the 18th century, this method was already being used by Japanese fishermen. Indeed, they immersed various shelters and put in place rafts in order to improve their catch. Throughout the past thirty years, hundreds of artificial reefs have been developed worldwide and research showed that small island states could draw some benefit from these reefs for their fisheries resources. Not only do these reefs increase the richness of the local marine life but they can also increase the catch of fishermen. They can also be used for the rehabilitation of habitats destroyed by natural forces or by human activities, and they also participate in the creation of reproduction zones. Attracted by their biological richness, they are frequently visited by divers which additionally constitute a considerable attraction for tourists.

However, it is important to note that such advantages cannot be simply procured by submersing solid materials in the sea. The success and survival of an artificial reef depends on efficient planning as well as a rigorous selection of sites. As such, just like a pearl gently develops around a nucleus, an artificial reef will be the foundation of a rich ecosystem.

The creation of artificial reefs in Mauritius began in 1981. When it came to materials, old barges and fishing boats that were abandoned in the port were chosen. Being both solid and voluminous, these materials were ideal to introduce into the sea in upwelling zones, which support the benthic and pelagic fishes. However, the utilisation of boats as artificial reefs requires lengthy preparation: thorough cleaning of vessels and the cutting of wedges and waterproof shells, to facilitate sinking. These operations and towing to sites sometimes involve a high cost for which funding is not always easy to find.

However, the success of the Mauritian example in the creation of artificial reefs with old ships has been such that, it was accredited for an international recognition in 1994 and was awarded the second prize of the Grand Prix International de l`Environnement Marin. The ecological richness of most of the Mauritian artificial reefs leads to the hope that such projects will be developed in the surrounding region. The MMCS is ready to share its knowledge and expertise in this field and hope that the island will not only be known for its shipwrecks of the past centuries, but also for its old scuttled wrecks, which along with taking a well-deserved retirement, have today become a source of life for marine animals.

The aim of this page is to give a glimpse on the concept of creation of artificial reefs in Mauritius. The history of each reef is completely detailed and the progress of the scuttling is described in the form of newspaper article extracts.

The MMCS wishes to thank all those who have helped in the various scuttling activities. First of all the Mauritius Marine Authority, without whom it wouldn't have been possible to obtain neither the raw materials nor the logistical support. Shell and Caltex for their invaluable help during the pumping up of hydrocarbons. The MMCS also wishes to thank Securiclean who helped a lot in the cleaning process. Thanks to all MMCS members, those forming part of the Mauritius Underwater Group (MUG), who were always present, as well as those of the Mauritian Scuba Diving Association (MSDA). Thanks also to all those whom have not been mentioned here.

The creation of artificial reefs in the sea favours biological productivity, therefore enhancing the population of fish and invertebrates. These reefs have the power to attract marine life by offering a habitat. They not only constitute a shelter but are also a valuable reproduction reservoir, which can recreate a whole ecosystem in biological depleted zones.

In Mauritius, the activities aimed at creating artificial reefs have been in development by the MMCS since 1980. The creation of such reefs mainly aims at:

  1. Increasing the marine population in the neighbouring reef areas
  2. An improvement in the fishermen's catch from these reef zones
  3. A study area for scientists
  4. A tourist attraction for divers
  5. A rehabilitation of the areas destroyed by natural forces or anthropogenic activities
  6. A creation of reproduction zones
  7. A beneficial use of solid wastes like old boats, tyres and automobile carcasses etc.

What are artificial reefs?

Artificial reefs are man-made habitats typically built to promote the growth of corals to develop reef systems and encourage marine life into the area. It mimics a natural reef.

By immersing old deserted ships in carefully chosen sites, the MMCS and, since more recently, the MSDA and the National Coast Guard (NCG) have created 13 artificial reefs (see cartography). Other objects, like old worn tyres have also been associated to these wreckages.

How do artificial reefs develop?

The colonisation of artificial reefs is done progressively. In the beginning, devoid of any form of life, they are rapidly colonized by weed and animal classes like sponges, hydroids, bryozoans, bivalve shells, barnacles, acids, anemones, halcyons, gorgons and finally, after a few years' time, by corals with calcareous skeletons like Acropora, Montipora, Pocillopora and Pavonia. This encrusting fauna and flora provide food for sedentary and mobile animals like sea cucumbers, starfishes, sea urchins, crabs and squids as well as small fishes like Snappers (Madras), Butterflyfish (Papillon), Priacanthus (Fanal), Triggerfish (Bourse), Demoiselle, Sergent Major etc. In turn, these small fish attract pelagic and predator species such as hinds, morays, Laffers, kingfishes, mackerels, Capitaines, barracudas, etc.


The Mauritius Marine Conservation Society and the artificial reef concept in Mauritius

The Mauritius Marine Conservation Society (MMCS) subscribes to the World Conservation Strategy philosophy and acknowledges the urgent need to conserve the coral reef and lagoon ecosystems of the Mauritian islands (Indian Ocean). Our coral reefs contain the highest biological diversity of all our ecosystems and are important in both an ecological and economical context; as a major tourist attractant, supporting an over exploitative fishing industry and as a local recreational outlet. The MMCS is a Non-Government Organisation (NGO) which was formed in 1979 by divers concerned by the degradation of the Mauritian reefs. Important aims of the MMCS include, creating a public awareness for the need for marine conservation, to re-establish reefs by means of artificial reef structures, and to generate an interest in the formation of marine parks.
At its formation twelve years ago, the MMCS recognised population growth, industrialisation, agricultural fertilizers, spearfishing, live shell collection and explosive fishing as the prime causes of marine environment degradation. It further recognised the need for specialists to identify and quantify the degradation as this was beyond the capability of the MMCS. However, the role of public opinion and awareness by legislators of the deteriorating situation in the lagoons and reefs were believed to be essential precursors to effective conservation of the marine environment.

This resulted in the motto "Conservation through Education" and an on-going campaign to change public opinion through positive ameliorative action.

Artificial reefs have been created for centuries by fishermen intent on increasing their catch. Virtually any inert floating or fixed structure in a water body, serves to attract aquatic life, which uses the structure for shelter, attachment, navigation orientation, spawning site or feeding area. Mauritius a tiny island in the Indian Ocean has installed many fish aggregating devices or FAD's around the coast since 1986. The Mauritius Marine Conservation Society has sunk 13 vessels around Mauritius since 1980, in depths of 12 to 73 meters of water.

Considerable research has been conducted on how the artificial reefs work and what structure best serves to aggregate marine life. The Japanese especially have developed considerable expertise in the form of their coastal fisheries enhancement programmes. Efforts in the United States have centred mainly on the profitable use of non-functioning oil rigs as FAD's as well as the use of waste materials (building wastes, tyres, vehicles) for industrial and recreational fishing. Without any doubt, artificial reefs offer tremendous potential for habitat enhancement.

However, two major points arise from the concept. Firstly, there is still no consensus why artificial reefs attract marine life, although it does seem that inshore structures provide feeding, breeding and shelter functions, whereas pelagic structures primarily provide navigation and feeding functions. Secondly, the debate whether artificial reefs increase biological productivity or merely concentrate marine life forms is not resolved. However, it does appear that localised enhancement of productivity in coastal areas can occur. In the pelagic zone, this is more likely to be a concentrating phenomenon, where fish are concerned.

In Mauritius, an evaluation of the pelagic artificial reefs, the FAD's suggests a viable alternative for inshore fishermen and perhaps a respite for the over-fished lagoons around Mauritius. The MMCS has recently embarked on an evaluation of the artificial reefs, using underwater video and visual surveys. All but one artificial reef have been repeatedly visited over years since their creation. Immediately apparent at most of the wrecks is the creation of oases of life in areas previously deserted of fish. All 13 artificial reefs attracted pelagic fish species within weeks of their sinking. All artificial reefs now harbour various numbers of resident benthic reef fishes and pelagic fishes as well as crustaceans, molluscs and algal species. Most have been colonised by coral species, soft and hard, the exceptions as a result, it is believed, of depth and site. The wreck structures themselves have been nearly completely covered with algal growth and harbour populations of the smaller invertebrate groups. The artificial reefs in water less than 25 m deep commonly have 30 to 50 species of fish around them, frequently numbering tens of thousands in number. The artificial reefs in shallow water are particularly rich in attached fauna and have a species rich collection of associated fishes. The MMCS is actually gathering all information available on the topic of artificial reef in order to go for a thorough monitoring program.

Many local fishermen know the location of the artificial reefs and fish on the sites. However, regular use of the wrecks as sport dive sites has to a large extent switched the use from fishing to diving, through the social and economic interchange of dive monitors, boatmen/fishermen and divers with fishermen.

The exploitation of the sites as dive rather than fishing sites thus appears to accord relative satisfaction in most cases. Popular dive sites are those rich in marine life. Both tourist and local divers use the sites, primarily from the adjoining hotel dive centres and the Mauritius Underwater Group. The proximity of a wreck dive is of undoubted benefit to divers and especially to centres which cater for tourist divers.

The initial artificial reef concept of MMCS was to ensure total protection of the wreck sites as "mini-reserves". However, lack of control over fishing and diving on the wrecks put paid to this idea. It has become increasingly clear that the absences of the necessary laws and of an effective law enforcement vehicle are major constraints to the creation of reserves. Nonetheless, even with laws and protective services, we believe that the co-operation of parties with vested interests, such as local divers, boatmen, fishermen, and hotels, will be necessary for effective protection.

The MMCS currently is working towards this latter objective in order to create areas which are effectively protected through vested interests, until such time as laws are promulgated.

The Mauritius Marine Conservation Society
c/o Mauritius Underwater Group
Railway Road