Artificial Reefs

Artificial Reefs in the Algarve

Artificial Reefs

Artificial Reefs: general aspects and the Portuguese experience

The widespread availability and accessibility of fishing resources on the coastal strip has ensured that these have always been the backdrop for strong fishing activities, which are the cause of somewhat significant imbalances in these ecosystems, with consequences that extend beyond the species exploited.

It can also be noted that traditional fishing regulation measures (for example: minimum sizes, restrictions on the activity of fishing, minimum net mesh sizes etc) have been shown many times to be insufficient or even ineffective to guarantee the sustainability of fishing and the environment.

On the other hand, we can see a growing diversification of uses of the coastal strip, with the expansion of eco-tourism (for example: diving and sports fishing), extraction of petroleum and natural gas, we well as new offshore activities - aquaculture and the production of energy from wind and waves. It is amid this reference framework that is considered imperative to find alternative measures that help with inverting (or at least stabilising) the current trend of environmental degradation of this strip (for example: the decrease in marine biodiversity and fishing resources), as well as promoting order among the activities that are carried out there, in a way that guarantees the sustainable exploitation of resources and environmental balance.

Artificial Reefs (ARs) given they have been developed in recent decades, are a contribution towards the resolution of these problems, being presented as an integrated marine ecosystem management tool and for activities related to the exploitation of fishing and energy resources.

But what ultimately is an artificial reef? Although a universally accepted definition does not exist on what an artificial reef is, in Europe it has been possible to arrive at consensus between those who are dedicated to the study of these artificial habitats [1], who define an artificial reef as "a structure deliberately placed on the sea bed, totally submerged, that seeks to imitate some of the characteristics of natural reefs".

Artificial reefs can therefore be considered to be structures as diverse as: steel or concrete units, industrial relics (for example: old ships, petroleum extraction platforms and the shells of cars, aeroplanes and other types of transport; and low cost bulk materials such as tree branches, bamboo, stone etc).

Historical aspects and their working principles

How did artificial reefs come about and how do they work?

The first artificial reef may have appeared in any location with a tradition of fishing because the capacity of a submerged structure to attract different life forms is well known to any fisherman.

However, the first recorded example is in Japan where, according to Ino [2], in the sixth year of the Kansei Era (1789-1801) a fisherman from the town of Manzai (Province of Awaji, on the Island of Awaji, South of Kobe), when fishing with a gochi-ami (a small purse-seine) made a capture, by chance, of thousands of pargos together with some remnants of a sunken ship.

Some years later, when the remnants of the ship disappeared, the fish stopped schooling in that area.
It was at that point that locals decided to sink large wood and bamboo structures attached to sandbags. A few months later, the shoals reappeared and the catches were bigger than those that were taken where the sunken ship had been.

The popularity of artificial reefs is largely derived from the basic principles of the way they work, because any structure at the bottom of the sea will bring about light changes to the currents that are the source of sound.

Fish detect those sounds. Out of simple curiosity, they are attracted to the reefs. On the other hand, the majority of the materials used in the construction of ARs make up a sub-stratum for a large and diverse range of marine invertebrates to attach themselves to.

In this way, the basic conditions for the creation of food chains are set in place, and the more heterogeneous the structure of the reef, the more complex the food chains are.

Applications of artificial reefs

Their initial use of ARs as structures used exclusively for increasing fish stocks has been overtaken to a large degree by a widening range of applications, specifically in the ecological sphere, contributing towards the increase in biological production, the promotion of marine biodiversity, the protection of young populations and the revitalisation of ecosystems etc.

Another area ARs are used for in an expanding way is related to leisure activities, such as diving, sports fishing and even surfing.

However, any artificial reef, regardless of the proposal underlying its creation, should bring together a set of characteristics that should guarantee that it remains friendly to the environment, in that it should not cause a negative impact from the environmental standpoint (for example: pollution caused by the escape of toxic materials); structurally stable, in a way that ensures that they do not come loose or fall apart in adverse conditions; a place where marine life will attach itself and multiply, without altering the natural balances of the area where it is implanted; and finally, to be of a sufficient size that it will achieve the objectives it was designed for.
Japan was the country that pioneered and was the world leader in the use of this type of structure. It is therefore natural that it was in Asia that large AR projects have been developed.

In Europe, Italy and Spain are the countries other than Portugal that have invested in this technology the most, although others like the UK, France, Greece, Turkey, Norway, Sweden and Poland are starting to take important steps in this direction.

However, the history of artificial reefs is not only made up of large projects, given that across the world, they are used in order to increase fishing stocks. Based on initiatives among small groups of fishermen, who principally make use of low cost raw materials in their construction, they are quite popular in many countries around the Indian and Pacific Oceans (for example: the Philippines, Thailand, India, Malaysia and some Polynesian islands) and in the inter-tropical zones of the Atlantic, whether off the coast of Africa (for example: Senegal and Ivory Coast), or America (for example: Mexico and the Caribbean).

The success of this type of project is often called into question, because in contrast to large projects, they are not subject to planning or advance study, and due to this they have a relatively short lifespan and weak structural stability, sometimes causing undesirable effects.

One of the most recent uses of ARs is derived from their use for reasons of environmental recovery, whether as tools to dissipate the effects of high-impact fishing (for example: trawling in coastal zones), or for the recovery of sea beds destroyed by various types of human activities.

However, one of the most common uses of ARs is connected to leisure pursuits, such as fishing and diving. These initiatives are particularly popular in the United States and Australia, where some of these have achieved great success, generating millions of dollars in a short period of time.

The artificial reefs of the Algarve Coast

The implementation of Artificial Reefs in Portuguese coastal waters is relatively recent. In 1990, and benefitting from the financial support of the Integrated Regional Development plan [Plano Integrado de Desenvolvimento Regional] a pilot project was embarked upon on the Algarve coast, following the Japanese philosophy, with the aim of assessing the effects of these structures on an environmental and fishing level, in a local context.

The choice of the Algarve coast is due, overall, to the fact that in the area there are a set of conditions that international experience recognises as essential for the development and success of projects of this type, specifically:
  • The existence of natural coastal accidents that provide large-scale availability of young fish population of great commercial interest;

  • Moderate sea conditions compared to those of the west coast (waves and currents), fundamental for the stability and operation of the reefs;

  • Scarcity underwater rock formations, particularly on the eastern Algarve;

  • The Intense exploitation of coastal fishing resources, with frequent impact levels on young fish stocks;

  • A large number of fishing boats operating on the coastal strip whose activity is highly dependent on local resources.


The results of the IPIMAR study

The results of the study, which lasted for six years, gave evidence that these ARs worked well, resulting in - among other aspects - a rise in biological production in their area of influence, in good rates of occupation, in a raised capacity for the accommodation of young fish stocks and a substantial increase in catches.

Following this pilot project, between 1998 and 2008 and under the scope of IFOP, IPIMAR developed a programme whose main objective was the creation of a reef complex along the Algarve coast made up of seven reef systems (see attached map), whose installation was completed in June 2003.

This reef complex, whose cost reached 7.5m Euros (75% of which was co-funded by European funds), is today the largest of its type in Europe and one of the largest in the world.

Extending over more than 43 square kilometres (an area equivalent to 4,300 football pitches), it is estimated that its area of influence is close to 67 square kilometres.

As such, the use of two types of concrete unit (see illustration) with a volume of 2.7 and 174 cubic metres of unit weight and 3 and 40 tons, respectively. Made up of close to 20,000 modules (with a volume of over 100,000 cubic metres), it is organised in reef clusters and groups (see graphic), in a way that its area of influence can be maximised and allow for the fish to circulate.

With the sustainability of small-scale fishing in the region being the key desired effect, this programme demonstrates its impact on different levels:
  • Bio-ecological - through the (i) development of new "habitats", enriching the coastal zone in a relatively broad stretch, the (ii) significant rise in the accommodation and protection capacity of the Algarve coast, (iii) and the contribution towards the recovery of coastal fishing resources, more than anything those that are subjected to the most intensive exploitation.

  • Management of fishing resources - through (i) a rise in the availability and diversity of resources for fishing activity, the (ii) creation of new conditioned fishing areas, (using more selective and/or less damaging methods for the environment), and the (iii) rise in profitability of fishing.

  • Planning of fisheries and coastal aquacultural activities - putting alternative fishing resource management practices into effect, with an innovative and integrated character, combined with other activities, specifically offshore aquaculture and eco-tourism.

  • Socio-economic - a consequence of the above-mentioned effects.

As a final note, we cannot escape from highlighting that any strategy for development and management of integrated fishing resource management will only be viable if a there is a commitment to a close involvement with fishing communities and other agents who, repeatedly, have made us feel that they support this initiative. We believe, as such, that the artificial reefs will operate as catalysts for the interest of various economic sectors, with a view to participatory management of these zones, thus empowering the role of artificial structures as instruments of coastal ecosystem revitalisation, as well as the planning and integrated management of activities on the coastal marine strip.

Almost 20 years after the first work, this IPIMAR programme is considered by the international scientific community to be an exemplary case in the artificial reef domain.

For this reason, it has become known at international level and the people involved have been invited regularly to present the results achieved to professionals and managers from the fishing sector, but also to those responsible for integrated coastal management policies in the wider world.

However, this initiative has also not suffered from being misunderstood in our country, with IPIMAR having recently received various requests for technical support, specifically from regional authorities interested in developing similar projects in their Counties along the while Portuguese continental west coast.

Typology and organization of an artificial coastal reef

[1] European Artificial Reef Research Network (1998)

[2] Ino T. 1974. Historical review of artificial reef Activities in Japan. Proceedings of the International Conference on Artificial Reefs, March 1974, Texas (USA): 21-23 pp.

Author of this article: Miguel Neves Dos Santos
- IPIMAR Researcher
- Scientific Coordinator of the implementation of artificial reefs on the Algarve Coast.

Source, Copyright and original article: Portuguese Navy Magazine (2009, May 12).

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