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Reef Restoration as a Fisheries Management Tool

Thomas J. Goreau and Wolf Hilbertz

Global Coral Reef Alliance, Cambridge, MA, USA

Keywords: Coral, reef, fisheries, habitat, standing stocks, carrying capacity, overharvesting, degradation, restoration.

Contents

1. Introduction: coral reef fisheries

2. Coral reef fisheries decline

3. Causes of decline: overfishing

4. Causes of decline: habitat degradation

5. Marine Protected Areas in reef fisheries management

5.1. The Marine Protected Area (MPA) Strategy

5.2. Top down and bottom up MPAs

5.3. Global change and MPAs

6. Natural reef regeneration

7. Restoration methods

7.1. Stress abatement

7.2. Artisanal restoration

7.3. Artificial reefs

7.4. Coral growth on exotic materials

8. Electrical reef restoration

8.1. A promising new coral reef restoration method

8.2. Coral recruitment

8.3. Fish and invertebrate recruitment

8.4. Mariculture

8.5. Shore protection

9. Conclusions

Bibliography

Glossary

Biographical Sketches

 Summary

 Coral reef fisheries feed nearly a billion people, almost all in poor tropical countries. Conventional strategies of coral reef conservation and fisheries management focus on controlling fishing within limited “protected” areas, but generally ignore habitat quality or global changes, which are increasingly rendering the methods of the past obsolete and ineffectual. Yet the precipitous ongoing decline of coral reef fisheries stems from habitat degradation as well as over-fishing and cannot be reversed without restoring habitat quality in damaged areas. Reef habitat degradation is largely caused by external stresses like high temperature, new diseases, and land-derived pollution, which kill corals, reduce biodiversity of food supplies for harvested species, and are beyond the capacity of any marine protected area (MPA) to control. Without large-scale restoration of habitat quality the decline will continue, even in the well-managed and funded MPAs. Due to the accelerating pace of coral mortality from global warming, sea level rise, land-based sources of pollution, and new disease pathogens, new generations of fishing methods are needed that restore habitat quality, fisheries carrying capacity, and standing stocks in degraded areas. Future coral reef fisheries management will require new methods to grow corals faster and more resistant to environmental stress, and to enhance recruitment of corals, fish, and shellfish. Conventional methods of reef restoration fail when water quality deteriorates from excessive temperature, pollution, or sediments. In contrast the Biorock method of coral reef restoration greatly increases coral growth rates and survival from stress, allowing rapid recovery of coral reefs where natural regeneration has failed, greatly increasing fish and shellfish populations, and even turning severely eroding beaches into growing ones. This is done without monoculture or food addition, and avoids the genetic impoverishment, disease, and nutrient pollution problems of conventional mariculture. Some fisherfolk in Indonesia, the Philippines, and elsewhere are now using the Biorock method to grow whole reefs and become sustainable harvesters of the ecosystems they create and manage. This proven technology is easily taught to fisherfolk and applied on a large scale at low cost. Fishing communities are eager to expand their knowledge, skills, and sustainable productivity, but need training in new methods and capital to apply them. Unfortunately there are still currently no mechanisms to provide the resources needed to allow fisherfolk to change from destructive hunters to restorative reef farmers. A paradigm shift is needed by policy makers, funding agencies, conservation groups, and fisheries management organizations in order for this new method to be implemented. Fundamental research is also needed into the genetic factors affecting stress response and resistance, to tide coral reefs and their fisheries over until the fundamental causes of long-term deterioration can be reduced and greatly minimized.

 1. Introduction: Coral Reef Fisheries

 For over 100 countries worldwide coral reefs are the major source of marine biodiversity, fisheries, sand supply, tourism, and shore protection, and would be the most valuable ecosystem they have, per unit area, if the economic and environmental services they provide were properly accounted for. Yet almost everywhere on the planet, coral reef ecosystem services are rapidly vanishing or lie in ruins. Because human users do not pay directly for coral reef services, they treat this valuable ecosystem with disregard as common free goods, in the false belief that reefs as an infinite resource capable of unlimited exploitation that will endlessly replace itself at no cost to those who exploit it. The true economic value of healthy coral reefs will only be appreciated when countries must import fish to keep poor people from starving, import sand so that tourists have nice clean beaches to lie on so that locals can get jobs in the tourism industry that is the major development strategy of most tropical islands, and when protective sea walls must be built all along the coastlines to prevent hotels, roads, airports, and houses from drowning by the rising seas. Coral reef environmental and economic services are estimated to lie in the range of up to millions of dollars per kilometer of shoreline.

 Coral reef fisheries are the major source of protein for nearly a billion people, mostly in developing countries. Like almost all fisheries worldwide, reef fisheries are long known to be in a state of advanced decline but the magnitude of the decline is hard to estimate because almost all coral reef fisheries is artisanal, and the catch is locally consumed by the families of the fisherfolk, bartered or shared with their neighbors, or sold locally. With the exception of a small number of high value items, such as sea cucumbers, spiny lobsters, Caribbean queen conch, giant clams, live fish, aquarium fish, shark fins, and sea urchins, most of the reef fish and shellfish catch does not enter the international export market, and so is usually not tabulated in national or United Nations Food and Agriculture Organization (FAO) fisheries statistics. Even where reef items are reported, the reported values are often guesses due to lack of information or even serious underestimates due to deliberate under-reporting. Because most fishermen are poor and receive minimal public services, fisherfolk are often suspicious that efforts to find out how much they catch is covertly aimed at taxing them or dispossessing their resources for the benefit of foreign or local elite investors, making fishermen reluctant to divulge their true catches except to those who have earned their trust.

 Unlike non-reef fisheries, where the catch focuses on a relative handful of valuable species, coral reef fisheries are far more diverse. This is unsurprising given that coral reefs have hundreds of times more species per unit area than the open ocean. Around a quarter of all fish species are reef dwellers even though coral reefs only cover around 0.1% of the area of the oceans. Furthermore many of these species are very poorly known. For example recently more than a hundred species of fish unknown to science were found on sale in markets on the island of Bali, Indonesia alone. The recent expansion of mariculture, which concentrates on a few high value products like salmon and oysters, has begun to expand in the tropics, but the products, like shrimps, prawns, and milkfish, are largely farmed not in reef habitats but in adjacent shallow estuaries or low lying mangrove habitats, and the loss of soil and nutrient retention by mangroves has caused serious damage to coral reefs and their fisheries wherever large scale coastal mariculture has been introduced.

 2. Coral Reef Fisheries Decline

 Virtually everywhere in the world where reef fishermen are interviewed they report that catches have severely declined in recent years. This is shown by the disappearance or extreme rarity of species that once were common, dramatic decreases in numbers and sizes, and shifts from more desirable to less desirable species. Almost everywhere the oldest fishermen remember an abundance and size of species that younger fishermen have never seen, and which the latter generally believe to be either “fishermen’s tales”, the delusions of senile old age, or outright lies. Yet it is those who claim that there has been no change who are usually wrong, sometimes because they have been fishing for too short a time to notice changes, because they are unobservant, have forgotten how things used to be, or because they simply distrust authority and fear that claims of decline will be blamed on them and used by government authorities who they frequently do not trust to prevent them from fishing.

Fishermen virtually everywhere report similar tales. For example one fisherman in Jamaica reported that he used to catch so much that he would give away enough fish to feed his entire village, but now can barely catch enough for a little occasional fish soup for his family alone, and must turn away friends who come begging for “just a little piece” of fish. The chief of a Kuna Indian village in Panama said that everybody in his village used to catch 10 or 15 lobsters every evening right in front of their own houses, but now they must paddle their canoes for hours, dive very deep, and only find fewer and ever smaller lobsters. Indonesian and Philippine fishermen who once had huge catches now are lucky after an entire day of fishing to come back with only a handful of tiny fish that are only enough to be boiled for soup.

Many fishermen now say that they no longer fish because they expect to bring anything back, and only go to sea with no expectations because fishing is a way of life that they love, but they cannot expect young people to follow them. These stories are essentially universal, and the few rare exceptions, such as one case of a Polynesian atoll with so few people and such a large area of reef that the fishermen are still able to catch all their needs next to their village and have no idea of reef condition further away, only prove the general rule. Fishermen must go to further and further and deeper and deeper to find enough to bring back. In place after place, fishing communities around the world complain that they are on the verge of starvation in locations where catches were once so plentiful that even incompetent fishermen were well fed by their neighbors’ surplus catches. Fish that were once common catches become steadily smaller and smaller and then disappear, and fishermen switch to less desirable species, until they too are gone, fishing down the food chain.

A classic case of this transition is in Jamaica, where in the 1950s the fish catches were overwhelmingly made up of fish-eating fish species, followed by invertebrate feeders, and the few algae eating fish species were regarded as inedible. The desirable food species like groupers, jacks, and barracuda were wiped out sequentially by overharvesting, and at the same time nutrient pollution of the coastal zone by sewage and fertilizers over-fertilized the algae. The increase in land-based nutrient sources caused algae to proliferate, overgrowing and killing the coral reefs, which resulted in the loss of most of the invertebrates like crabs, shrimps, and worms which fed the majority of the fish species that the carnivorous fish ate. As a result the fish populations are now almost entirely made up of algae eating damselfish, parrotfish, and surgeonfish, which are now so intensively fished that few can reach reproductive age, so their source comes from larvae washed by currents from other parts of the Caribbean where these species are still not eaten. Ironically, although the fishermen were the first to notice that the reef fisheries were being killed by land based sources of pollution from coastal tourism development, foreign scientists blamed the fishermen, who they claimed had eaten all the algae eating fish and caused the algae to grow. In fact there is now no shortage of herbivores, and the fish population is now almost entirely algae eaters because this is the only source of food remaining after the formerly rich coral reefs turned into dense algae lawns.

3. Causes of Decline: Overfishing

The causes of fishery decline are complex but are largely well known. Coastal populations are rapidly growing, and population pressure is a key part of the declines in catch per unit effort. Over-fishing is now virtually universal, not only near populated shores, but also far from them, as fishermen range further and further. Few reefs anywhere in the world are not well known to fishermen, even where they are completely unknown to the scientific community, including very deep reefs that cannot be seen from the surface. Even the most remote reefs are reachable by large motorized boats, often belonging to wealthy countries, which strip all the fish they can find. The boats from developed countries have sophisticated sonar systems allowing them to find all the fish schools and wipe them out using large nets. In the Lembeh Strait of Sulawesi, Indonesia, foreign poachers stretched a net across a major migratory route for marlins, sharks, dolphins, and whales, wiping them out in short order. Subsistence fishermen are forced to use more and more destructive methods to feed their families. A very extensive recent study by the Law of Nature Foundation in the Visayas Sea area of the Central Philippines, formerly one of the richest reef fisheries in the world, reported that “not a single hectare of reef remained intact” from escalating use of bombs and cyanide poison by fishermen. One reef in this area went from 80% live coral cover to 2% in just two years. In Indonesia spectacular pristine reefs discovered by tourist dive boats in extremely remote locations have often found the following year to have been turned into mere piles of rubble caused by blast fishing.

A classic example is the destruction of the fisheries resources of Hotsarihie (Helen Atoll) south west of Palau, which has been reported to have the greatest diversity of fish, corals, and shellfish of any Pacific Island reef. This atoll was uninhabited because the huge reef has only a tiny shifting sand bank with no fresh water, but it belongs to the people of Hatohobei (Tobi), some 80 kilometers away. Hotsarihie used to have the richest giant clam (Tridacna sp.) and precious shell (Trochus niloticus) resources in the entire Pacific (the name means Reef of the Giant Clam in the Tobian language). But these resources were plundered by poachers from Indonesia, the Philippines, Taiwan, until finally one foreign factory ship came and within a few days, removed most of the Tridacna sp. and T. niloticus, leaving a wasteland behind. After the poaching, almost all of the corals bleached and died from heat shock in 1998, causing a further crash in reef fish populations.

In recent years the market for sea urchins, sea cucumbers, shark fins, and live fish has expanded from a regional market in Southeast Asia to a global market, causing rings of depleted resources to expand outward. Once fishermen discover that previously unexploited resources like sea cucumbers and sea urchins, which were locally regarded as inedible, can be sold to foreign buyers for large amounts of money, these resources can vanish practically instantaneously in the most remote parts of the globe as a consequence of opening up a new market.

4. Causes of Decline: Habitat Degradation

 Overfishing is the traditional explanation for the catastrophic decline in reef resources that is found almost everywhere. But in reality this is only one component of the problem. Habitat degradation is as severe in most places. The correlation between fish abundance and diversity with live coral cover and diversity has been demonstrated over and over again on many spatial scales. Corals are vanishing worldwide, and with their disappearance the habitat that supports large and varied fish populations is endangered. Without food and shelter, fish rapidly vanish even where there is no fishing activity.

Coral reefs are the most fragile of ecosystems, and levels of stress that would not harm any other marine ecosystem will kill corals, which are adapted to the cleanest, clearest sea water. The causes of reef decline are well known. They can be classified into local, regional, and global components. Local causes of damage are due to stresses that act on small spatial and temporal scales, like hurricanes, typhoons, and cyclones, ship groundings, anchor damage, diver damage, and damaging fishing methods like use of bombs, poisons, and nets. Regional damage results from impacts from adjacent regions, primarily land-based sources of pollution such as nutrients from sewage runoff, agricultural, lawn, and golf course fertilizers, red tides (often caused by land based sources of nutrients), pollution from oil spills and toxic chemicals, and sedimentation caused by deforestation and bad land management. Global causes of reef death include the impacts of global warming, global sea level rise, and new diseases.

 So many factors kill corals, and their rapid spread, increased intensity, and cumulative impacts of these stresses are such that the majority of the corals in the world have been lost in the last decade. Although many people claim that a significant amount of coral reefs have already been lost, this claim results from a semantic confusion between reefs and corals. In fact almost no coral reef structures have disappeared at all, although most of the corals have died. These erroneous claims result from a failure to distinguish between the geological structure of coral reefs and the living corals that slowly build it over millennia. The coral reef is the limestone framework built up by large corals, and it remains long after the corals have died, being only slowly broken down over years to decades through erosion by boring organisms and waves. Dead and dying reefs are vastly inferior habitat both for reef fishes, which require healthy coral for hiding places and the habitat for their prey food. But in most degraded reefs, even though the dead framework remains standing, the corals, the invertebrates, and the fish have almost entirely vanished.

Unless habitat quality is restored, in terms of shelter and food supply, the prognosis for future coral reef fishery recovery is poor even if there were no fishing activity at all. Moreover the death of many calcareous reef organisms eliminates the supply of new sand needed to replace that lost to storm erosion, while the wave-breaking reef framework itself breaks down from bio-erosion by boring organisms and increased physical forces from increased frequency and intensity of tropical storms. The natural protective mechanisms of healthy reefs that reduce wave energy at the shoreline are collapsing, causing increased erosion of most tropical beaches. This erosion will increase as global sea level rise, caused by thermal expansion of surface water and increased melting of glaciers and ice caps, accelerates.

5. Marine Protected Areas in Reef Fisheries Management

 5.1. The Marine Protected Area Strategy

 The standard solution to marine conservation and fisheries management issues currently being used by all governments, international funding agencies, and large conservation groups is the establishment of marine protected areas (MPAs). It is claimed by many scientists that by stopping destructive fishing practices in designated areas, the habitat and fisheries stocks will rebound by themselves to their prior levels, and moreover that the excess population will “spill over” to greatly enhance fish catches in surrounding areas used for fishing outside designated MPAs. These results are claimed to result from the dogma that coral reefs can bounce back from any stress due to their capacity for “natural restoration” and “resilience”. The benefits claimed have been shown in the case of a handful of very small MPAs in which fish populations have increased after they came under active management, and policy makers and funding agencies hope that all other MPAs will show the same results.

The results are heavily dependent on habitat quality, but this is usually glossed over by MPA proponents. Where the areas being protected contain coral reefs in excellent condition, the results can be rapid and dramatic, as shown in the classic studies at Apo Island and a few other sites in the Philippines. However where the “protected” areas have poor habitat quality the results show that coral cover and fish populations are no different than nearby reefs that have no management or protection at all. For example, a recent study of MPAs and nearby fishing areas in Papua New Guinea found that both protected and unprotected areas showed identical severe declines in both live coral and fish, with no effect of management found. The long term monitoring studies of the Great Barrier Reef Marine Park Authority and of the Florida Keys National Marine Sanctuary, the most lavishly funded and managed MPAs in the world, and often held up as models that should be emulated by all developing countries, show that live coral cover has steadily declined under management, and is down to only around 20% and less than 5% respectively. While there is little evidence that establishment of MPAs has halted the decline of the corals, there is some evidence that protection has resulted in higher numbers of some economically valuable, heavily exploited, long-lived, and slowly reproducing species, such as groupers and lobsters. Yet even if all the very small fraction of reef claimed to be “protected” could in fact be genuinely protected from all external sources of environmental degradation, this will not stem the catastrophic fisheries decline in the vast preponderance of reefs that have no protection whatsoever. Since most coral reef countries are poor, with vulnerable populations relying on subsistence fishing for the bulk of their protein sources, fishermen will have no choice but to invade any small remaining reef areas in good condition to feed their families.

5.2 Top Down and Bottom Up Management Strategies

There are two fundamental models for MPA management, the bottom-up and the top-down. In bottom-up MPAs fisheries management is community-based and relies on consensus of the entire community to manage marine resources in a way that nourishes the whole community while sustaining their marine resources, rather than hastening their destruction through over-exploitation. In the top-down MPAs, especially those in developing countries, which are often established by foreign consultants employed by international funding agencies and conservation groups, fisheries resources are protected using superior force to prevent local residents or outsiders from exploiting them in designated areas or by banning use of specified destructive fishing methods. This is a model that has been carried out by the Komodo National Park in Indonesia. Unfortunately this model often overlooks the rights of local communities, and this negligence can sometimes lead to conflict.

Such conflict will probably become more intense if the top-down, externally-managed MPA model expands, unless large-scale restoration of degraded areas to increase sustainable fisheries carrying capacity is efficiently implemented in surrounding areas used by subsistence fishermen. Yet unfortunately at this point there is inadequate funding, and not enough personnel trained in restoration of degraded fisheries habitat. It is unfortunate that there is still misunderstanding among developers who promote top-down management models, and who remain skeptical about possible restoration of areas outside MPAs, since they claim, without solid scientific evidence, that restoration is not really needed because they (wrongly) believe that ecosystems will regenerate themselves, unaided, despite clear failure of damaged fisheries to recover in place after place.

There is little evidence that MPAs have resulted in a sustained large scale increase in live coral cover and fisheries habitat quality. Most MPAs are full of dead or dying corals because even the most well-intentioned and funded MPAs are powerless to control or reverse coral habitat degradation from external factors. Too often the complexity and diversity of coral reef ecosystems are misunderstood and methods and techniques designed to assess, monitor, and control fishing efforts designed in much less diverse cold water fisheries, are often irrelevant. In a particularly dramatic and unfortunate case, MPA efforts to protect an endangered marine mammal, the dugong, and the highly diverse coral reef fisheries in Milne Bay, eastern Papua New Guinea, were abandoned due to a wrong initial assessment of the project and its high cost of operation and maintenance.

5.3. Global Change and Marine Protected Areas

Almost every coral reef in the world is nowadays severely degraded or damaged, including those within MPAs. Even if every reef remaining in good condition were managed by MPAs with unlimited resources, they could still not by themselves stem decline caused by water quality deterioration from sources outside MPA boundaries. These include increased temperature caused by fossil fuels, increased nutrients caused by failure to treat increasing human wastes adequately, and the proliferation of microbes bearing new diseases. These “external” factors, both natural and man-made, completely prevent restoration of fisheries carrying capacity in most coral reefs. Only a few lucky locations have had minor damage to date due to minimal rises in sea temperature, nutrients, and pathogens, but such protection is more due to fortuitous geographical accidents of ocean circulation than the result of deliberate management.

MPAs, if properly funded and managed, can prevent local damage caused by human activities within the MPA boundary (e.g. destructive fishing, dredging, anchors, divers), but they are ineffective against stresses emanating outside their boundaries, and so will fail increasingly as these external threats become even more important in the future (e.g. rise in sea surface temperature). Unless the external factors that prevent natural regeneration of reefs damaged by destructive and unsustainable fishing methods are understood and controlled, MPAs cannot result in the improved habitat quality needed to increase the standing stocks of fisheries species. Since the major factors killing corals, such as global warming, new diseases, and land-based sources of pollution, are out of control everywhere, MPAs can only succeed where the water quality is excellent, where pathogens cannot be transported by currents, and where global warming is not taking place.

However failures of top down MPA models are more systemic than the lack of long term resources. MPAs will not succeed in the long run unless the root causes of global reef deterioration, global warming, new diseases, and land based sources of pollution, are eliminated through reducing atmospheric carbon dioxide by switching to renewable non-polluting fuels instead of oil, coal, and natural gas, replanting degraded hill slopes to prevent soil erosion and increase carbon sinks, universal use of tertiary sewage treatment with recycling of all waste water nutrients on land, efficient use of fertilizers and animal wastes, and more accurate and relevant research to understand and hopefully control the pathogenic vectors responsible for the new diseases killing corals, sponges, algae, fish, and other marine organisms on a steadily increasing scale. More insight is needed on how these disease pathogens originate and spread, otherwise no effective management recommendations can be made to contain or mitigate their devastating effects on the coral reefs. The development of recent molecular methods to rapidly amplify the genetic sequences of all the bacteria found in natural marine ecosystems, including the roughly 99% of bacteria that cannot now be cultured, provide powerful tools for such research, but unfortunately there is still too little applied marine microbiological research done, in particular in developing countries. The importance of such work has been highlighted in recent studies showing that most pathogens causing new coral reef diseases grow faster and are more virulent at higher temperature, so global warming will amplify their negative impacts on reef ecosystems.

6. Natural Reef Regeneration

In the past, when coral reefs were devastated by excessive physical forces (e.g. hurricanes, typhoons, cyclones, storm waves, tsunamis, volcanoes, ship groundings, or anchor damage), they would regenerate typically in two to three decades. In all these cases the stresses were very localized in both space and time; healthy coral reefs were found immediately outside damaged areas and contributed to the recolonization process with living larvae reseeding damaged areas, and their water quality was sufficiently high, with low sediments, nutrients, and temperature, that there was plenty of clean substrate allowing coral larvae to settle and grow.

Charles Darwin, in his first book, On the Structure and Distribution of Coral Reefs (1842), noted that corals could not grow in dirty water (then largely confined to river mouths and large ports). He cited the Edinburgh University thesis of Allan (who fixed broken coral heads with wooden stakes so that they could not move in waters three feet deep in Madagascar, and noted that they continued to grow between 1830 and 1832) and a report by Thomas de la Beche, (the Jamaican geologist who founded the British Geological Survey) quoting observations by Lloyd (who placed broken corals in a protected tide pool in Panama and found them firmly attached to the bottom by new limestone growth in just a few days) as critical evidence that corals could recover from physical damage and continue reef building as long as they were in clean water and protected from damage caused by rolling around.

Nowadays the severe deterioration of water quality caused by global warming, sedimentation, and unchecked eutrophication caused by untreated sewage, fertilizer, and wastes have steadily reduced the areas of clean hard substrate on which broken corals can re-attach themselves or on which larval corals can settle. Currently coral larvae find the bottom increasingly too muddy and too overgrown with weeds to settle, and increasingly hot water killing them even if they are lucky enough to land on hard bottom just after a providential storm has swept away the mantle of sediments and algae from hard surfaces. These stresses have become virtually global in spatial extent, and getting progressively worse with time everywhere. As a result, those areas where natural regeneration can take place are constantly becoming less extensive. Even in areas remote from all human influences and land-based sources, global warming is killing reefs that are widely held to be pristine. In fact the mortality in such reef areas whose extreme remoteness had prevented human exploitation is even greater than in stressed habitat, because they entirely lack the stress-adapted coral species that increasingly predominate in areas near human influence. Soon there will be no refuges of healthy reefs to repopulate damaged areas.

 7. Restoration Methods

Coral reef restoration has long antecedents, preceding those known to Darwin. The major fundamental approaches to coral reef habitat restoration are summarized here.

7.1. Stress Abatement

The ideal restoration strategy would be to create conditions where restoration would be unnecessary, by removing all human-caused stresses to reefs so that natural regeneration could work again where natural disasters took place. Sadly, this is not likely any time soon. Management guides issued by international agencies avoid dealing with reversing global warming and new diseases, and focus on symbolic, but globally minor, stresses like anchor damage, tourist divers with poor buoyancy control, and public education to inform people of the role of reefs, which supposedly will “increase resiliency”. Even if these steps, needed for other reasons, were fully implemented, they would have little or no impact at all on the major causes of coral mortality from bleaching, diseases, or land-based sources of pollution, except on very small local scales. No one has yet abated the causes of global warming or new diseases, and the number of cases where nutrient pollution has been stopped, causing algae to rapidly die back due to lack of nutrients and allow corals to recover, is limited to a handful of places, to be contrasted with failure to stop or reverse accelerating eutrophication along almost all populated shorelines.

Coral reefs are among the hardest ecosystems to manage, because they are the ultimate downstream ecosystem, being affected by human mismanagement of energy, agriculture, land use, sewage, solid and animal wastes, and chemicals globally, and these stresses are constantly getting worse due to population growth and increased standards of living. In effect, to protect reefs in the long run energy sources, food supply, land use, and waste management must be sustainably managed first, and all of these problems must be tackled simultaneously everywhere. Active restoration on local scales seems to be the only interim action that can be taken until a global change of mindset takes place that allows humanity to seriously deal with global warming, pollution, and population pressures on the environment, and comprehensive, complete, and scientifically-sound environmental management systems are implemented on a global scale.

7.2. Artisanal Restoration.

Observant fishermen, seeking places where fish could be caught with the least effort, have long recognized that most fish are found where coral reefs are best developed. Divers see that fish crowd into coral habitat and are nearly absent in flat, muddy, or sandy habitats around and between reefs. Open ocean fishermen have long noted that pelagic fish congregate under any floating object large enough to cast a shadow, and Pacific island fishermen immediately head for any floating log or drifting object they can find, focus their fishing immediately under it as long as it remains in range, and will go to great lengths and distances to maintain exclusive possession of them. Structures of any kind, whether fixed to the bottom or floating, are clearly associated with elevated fish populations, so fishermen have sought to build structures to increase fish catches since ancient times, using many different materials. These include poles and fences stuck into soft bottom, bamboo rafts from which coconut palm leaves are suspended, and rock piles that are built up, left to mature, systematically dismantled to extract the fish and shellfish that have taken up residence, and then reconstructed. Throughout the Pacific and Southeast Asia people would build stone or bamboo weirs to trap fish populations migrating with the tides. In Indonesia fishermen built stone jetties to create crab and snail habitat.

The people of Hatohobei (Tobi), a remote low lying island of Palau in the Pacific, used to build large open frameworks of coral heads to create fish habitat, a method that has not been used for several generations. In the first descriptions of the Maldives written by outsiders in the 1300s it was described how Maldivians suspended coconut leaves in the water to create substrate for algae growth where endemic “Money” cowries grazed (Cypraea moneta), and their shells were harvested and exported across large parts of Asia and Africa, where they were used as currency. The species was not available outside the Maldives, and so were rare and could only be acquired through long distance trade. The age of this trade is shown by the fact that Maldivian cowrie species are commonly found in the Indus Valley archaeologically excavated sites 3000 to 4000 years old, while characteristic Indus valley beads have been found in the Maldives.

Sadly, most of these traditional artificial reef fisheries methods to enhance natural habitats have been abandoned. Steel hooks and plastic lines replaced traditional materials, and the introduction of indiscriminate fishing technologies (e.g. fine nets, long line hooks, bombs, chemical poisons, masks and fins, spearguns, motors, GPS, fish finding sonar) simply speed the pace of unsustainable exploitation that hasten fishery crashes.

7.3. Artificial Reefs

The current descendants of artisanal habitat modification methods are modern artificial reefs and fish aggregating devices (FADs), substituting plastic, styrofoam, and steel barrel floats for bamboo, plastic lines for coconut, pandanus, and hemp fiber ropes, and concrete, steel, rubber, plastics, ceramics, and fly ash for coral rocks. Yet from the point of view of coral growth the major change over the methods described by Darwin from the 1830s is the use of cement and epoxy glues to fix corals in place rather than wooden stakes, although the “discovery” that coral fragments will continue to grow if fixed in place is repeatedly made anew by those unfamiliar with the literature. These are basically differences in materials rather than qualitative or quantitative improvements in terms of the fundamental methods or the yields achieved. In the case of artificial materials used in FADs it can be argued that synthetic fiber ropes and hanging plastic strips last longer than bamboo and coconut and are therefore an improvement needing less frequent replacement.

While there is little doubt that fish will use any drifting or permanent object that provides shelter, and that creating additional structures significantly increases fish populations, the question is whether they are effective tools for coral reef fisheries restoration by increasing reef habitat and fisheries standing stocks or merely providing simple shelter that concentrates fish from elsewhere with no net gain in numbers. Artificial reefs and FADs can be used to greatly increase fish populations by increasing the total amount of habitat available, and hence total stocks, as long as they are sustainably managed to avoid overharvesting. Many marine researchers feel there is a role for artificial reef structures in both fisheries and habitat restoration especially when such structures are used by fishermen following sustainable management, as well as used to enhance habitat in protected “no-take” areas for fisheries stock restoration. So widespread is the belief of their effectiveness at fisheries habitat restoration that the Fisheries Departments of many countries not only encourage fishermen to dump concrete objects but directly subsidize such efforts.

However some marine experts oppose artificial reefs and FADs on grounds that these are simply tools for overexploitation of fishery resources, used by fishermen to strip reefs bare of fish. This assumption would be true if fishes so greatly preferred artificial structures that they abandoned real reefs. When artificial reefs are placed on flat mud or sand where there is no hiding place, fish congregate around them, but when they are placed near natural coral reefs, fishes shun them. In one dramatic case at Isla Mujeres, Quintana Roo, Mexico, many fish were found in hollow dome shaped concrete reefs with holes placed on a barren sand site at Manchones, while at a nearby site, Garrafon, where concrete artificial reefs are near a dead reef, fishes swarm around the dead reef corals but avoid the artificial reefs. This suggests that artificial coral reefs are inefficient fish aggregators unless they are remote from coral reefs or are covered with living coral.

There is clear evidence that artificial materials are less efficient than natural ones with regard to coral reef restoration as well as fish habitat. The community of organisms growing on reefs made from artificial materials is very different than that of adjacent natural coral reefs. Organisms growing on artificial reef surfaces are overwhelmingly dominated by hydroids, sponges, and soft corals, and not by hard corals. Such communities are sponge-soft coral communities, not coral dominated reefs. Most coral larvae are extremely fussy about substrate they will settle on, preferring clean limestone to all other surfaces. Only a handful of coral species will settle on any hard surfaces, and these few weedy and unselective species are the main ones found on artificial reefs.

The advantage of the conventional methods of reef restoration as described above is that artificial reefs can be sunk anywhere. The disadvantages of these methods are that artificial reefs made from exotic materials do not by themselves regenerate natural looking hard coral dominated ecosystems, from the point of view of either divers or fish. However live corals can be cemented and glued to artificial reefs with considerable labor, but coral growth rate is not increased, and coral survival depends on water quality. For example, large-scale conventional reef restoration projects in Fiji, located in areas of good water quality, were successful for a while, but all the corals died in 2002 when water temperature increased.

Most restoration projects have been done in places where the corals have died because of systematic pollution, almost all have been long term failures. In most cases glowing reports of immediate success were published right after implementation, without the long term monitoring studies that often would have shown a different picture. In the Maldives several hundred meters of concrete highway overpass roadbed were shipped from Newcastle upon Tyne, England, to Male in the Maldives, placed on top of a natural but dead reef flat where the corals had all been mined for construction material. Corals from another live reef were broken off and cemented onto the concrete. Virtually all of these corals died soon after, but only the immediate success and not the long-term failure was reported. Only a small amount of coral settlement on the sides and bottoms of the concrete slabs could be found a decade later, but the tops remain essentially a barren concrete wasteland.

7.4. Coral Growth on Exotic Materials

Artificial reef materials made of metals, concrete, ceramics, plastics, fly ash, or rubber also leach toxic materials that inhibit coral settlement for many years. Coral settlement usually only happens after a long and complex ecological succession where surfaces are first overgrown by a bacterial film, followed by calcareous encrusting algae, before corals can settle on the limestone film provided by calcareous algae crusts. Therefore, the rate of settlement of corals on steel, concrete, rubber, or ceramic substrates is far less than that seen on nearby reef rock. Many artificial reefs, such as wrecked ships, never develop much coral cover even after decades or centuries of exposure in coral reef habitats. Typical examples of concrete and ceramic artificial reefs with poor growth after several years are shown in Figures 1 and 2.

Figure 1. Concrete artificial reefs in Phuket, Thailand. The lower one is about 5 years old.

Photo by Thomas Sarkisian.

Figure 2. Ceramic artificial reefs in Manado, Sulawesi, Indonesia about 5 years old.

Photo by Wolf Hilbertz.

Major exceptions to this pattern of poor coral recruitment are those shipwrecks that carry a diverse variety of metals. Metals such as aluminum, magnesium, and zinc act as sacrificial anodes with respect to steel, which acts as a cathode, causing a flow of electrons between the different metals due to their varying electrical potential. This electrical current causes a rise in the pH on the steel surface, caused by the hydrolysis of water, stopping rusting and causing limestone minerals dissolved in sea water to precipitate on the steel surface, while the anode metal has low pH and dissolves. On the other hand lead, copper, brass, and bronze speed up iron dissolution and are themselves preserved. These electrochemical processes have protected almost all metal archaeological artifacts in shipwrecks. These artifacts are removed from the ocean as irregular lumps encrusted with layers of limestone that are dissolved away in acid baths or by wiring the limestone coated object to the anode of a battery to dissolve it and reveal the metal object beneath the limestone. Brass and bronze fittings in particular have been used on ships since ancient times. Many steel shipwrecks are observed to acquire a thin coating of galvanic limestone. However this process is limited by the amount of anodic metals on a particular shipwreck, and ends once they have dissolved away, usually within a few years. All shipwrecks that have developed hard coral settlement appear to have acquired a coating of limestone by galvanic action, on which corals settle, rather than on the bare steel.

A dramatic example of this process is the Liberty, the most dived on shipwreck in Asia, which hosts a diverse variety of hard corals as well as sponges and soft corals, and until recently held the world record for the highest diversity of fish species ever recorded at one site. The Liberty, a World War II transport ship, was deliberately run aground on a beach at Tulamben, Bali, Indonesia, in the early 1940s after it developed a leak and began to sink. The wreck remained on the beach rusting until 1963, when lava from Mount Agung pushed it back into the sea. While a thin electrolytic coating of limestone appears to have facilitated considerable coral settlement on the wreck, hard corals cover only a small proportion of the surface, and now that the anodic metals are gone, the remains are increasingly rusting. In the same time interval the lava that flowed into the sea nearby is now completely covered in hard corals in many places, showing that electrolytic coated steel is an inferior substrate for coral settlement compared to volcanic basalt.

8. Electrical Reef Restoration

8.1 A Promising New Coral Reef Restoration Method

A fundamental advance in coral reef restoration is the development of the Biorock method, which uses low voltage direct electrical currents to grow solid limestone rock on top of steel frames of any size or shape (with complete inhibition of rusting), thus producing the natural limestone minerals of which coral reefs are made. Biorock materials, also known as Seament, Seacrete, or Mineral Accretion, were developed in the early 1970s to grow limestone building materials of any size or shape in the sea. This method is similar to the natural electrolysis described earlier, and to methods used to protect marine structures like bridges and oil rigs from corrosion, but is sped up by applying a low voltage direct current and use of permanent and non-toxic anode materials. Since the 1980s this method has been used to successfully grow limestone reefs in more than 20 countries in the Caribbean, Indian Ocean, Pacific, and Southeast Asia.

Corals on Biorock reefs grow 3-5 times faster than typical reported rates, depending on the electrical current and voltage and the species, heal from damage almost instantly without releasing mucus (the normal sign of stress, control corals continue to release mucus for two weeks), and show visible growth within a day. These measured experimental growth rates were for corals grown just above the sand/mud bottom, and it is likely that they would grow even faster higher on the structure where corals receive more light, are less exposed to the bottom muddy layer, and benefit from more current-borne zooplankton food. Control corals on uncharged steel structures, while not directly exposed to electrical current, also appear to benefit from the electrical field. The iron to which they are attached acts as a passive cathode: two years later control steel rods had barely rusted, showing that they were cathodically protected by the current, which may also have elevated the growth of the “control” corals. In addition corals in the vicinity of the cables and the structures also have enhanced growth.

Biorock reefs rapidly build up dense fish populations, and are greatly favored for juvenile fish recruitment, even in muddy and nutrient rich waters. Sponges, tunicates, oysters, soft and hard corals, and other marine organisms spontaneously settle on them at high density and show exceptional growth rates, quickly converting them into richly diverse coral reef ecosystems surrounded by clouds of fish, strikingly unlike adjacent artificial reefs made of concrete. Examples of Biorock reefs of various ages in locations that previously were barren of live corals and had few fish are shown in Figures 3 to 6. Using Biorock technology, coral reefs can be kept alive where they would die from excessive temperature, mud, or nutrients, and new reefs can be rapidly grown in just a few years in places where no natural regeneration has taken place. These apparent advantages are unique to the Biorock method, and could probably be applied successfully where all other reef restoration methods fail.

Figure 3. Four month old Biorock reef in Lombok, Indonesia.

Photo by Emma Woolacott

Figure 4. Ten month old Biorock reef in Lombok, Indonesia.

Photo by Laurent Lavoye

Figure 5. 1.5 year old Biorock reef in Lombok, Indonesia.

Photo by Emma Woolacott

Figure 6. 3 year old Biorock reef in Bali, Indonesia.

Photo by James Cervino

Biorock corals in the Maldives had 16 to 50 times higher survival rates after bleaching than natural corals on adjacent reefs during the catastrophic 1998 bleaching event which killed around 95% or more of the natural corals. Corals on Biorock structures bleach just as those on surrounding reefs do, since this is simply the result of temperature stress on their symbiotic zooxanthella algae, but they do not die like surrounding corals do because they are apparently healthier and have greater metabolic energy reserves. At the Maldives sites where Biorock reef corals had 16 to 50 times higher survival rates after the 1998 bleaching event than adjacent natural reefs, thousands of corals had been previously transplanted using standard coral reef restoration methods with cement and epoxy onto concrete blocks or dead coral limestone. These were being used as controls to compare coral growth rates. All the transplanted control corals died after bleaching while most of the electrically charged corals survived.

Higher coral growth rates and stress resistance found on Biorock reefs are apparently because the corals and other organisms growing on Biorock reefs, may be making biochemical energy from the electrical currents and/or the electromagnetic field. While the biophysical and biochemical mechanisms have yet to be fully worked out and understood, it is well known that all organisms make biochemical energy from electrical currents flowing across the voltage difference between the outside and inside of their cell membranes. This voltage gradient is maintained at high metabolic cost to the organism, and so they physiologically respond by exploiting the currents and voltage differences that the Biorock method provides them at no energy cost to the organism.

Biorock reefs are composed of limestone and are hard coral dominated, in contrast to sponge and hydroids that dominate artificial reefs made of exotic materials. The difference is so striking that they are properly not called “artificial reefs” but “Biorock reefs” or “Coral Arks”. Biorock corals are more intensely pigmented, have higher growth rates and better developed branching and growth morphology than the nearby mother colonies they were transplanted from, although they are genetically identical and growing in the same environmental conditions. The difference is analogous to the difference in branching and leaf cover of genetically identical seeds planted in fertile soils versus poor ones. Biorock mineral coatings can be grown at up to several centimeters a year with a load bearing strength three times that of ordinary concrete. In addition, Biorock reefs produce the only marine construction material that is constantly growing, and which gets stronger with age instead of weaker like most other marine construction materials. They cement themselves to hard rock bottom, and are self-repairing, with the damaged areas filling in with new material and growing back preferentially. As a result wave resistant frames of any size or shape can be quickly grown. Shipwrecks can be converted into real coral reefs and completely protected from rusting and collapse.

The spectacular growth of corals and the huge clouds of fish around Biorock reefs that were grown in previously barren sites quickly make them major ecotourism attractions that have won numerous prestigious international environmental and ecotourism prizes. Tourists come from around the world to snorkel and dive on Biorock projects, and come back again and again to see their dramatic evolution and the constantly increasing density and diversity of fish. But given the large area of damaged and degraded coral reef, and the small number of areas where coastal resource use is dominated by tourism as opposed to fishing, it is clear that their major potential use lies in fisheries habitat restoration.

8.2. Coral Recruitment

Most reef organisms produce large amounts of larvae but are limited by predation and lack of suitable sites to successfully “recruit”. Any method that increases the quality of the recruitment habitat can make huge differences in their population size. Most reef species have planktonic larvae that must find a suitable reef habitat to metamorphose into juveniles and will die if they do not find the right material and environment to settle on in time. Most attached organisms with planktonic larvae, especially reef-building corals, are extremely fussy about suitable substrate. Clean limestone, free of sediment and algae, is critical to successful larval attachment and formation of the coral skeleton for most species, and is greatly preferred over other materials. Coral larvae will test a site for attachment, and if it is not suitable they will detach themselves and seek a better site, but can only do this a few times before they run out of energy. While free-swimming coral larvae are attracted to light (photophilic), they turn into shade seekers (photophobic) just before they settle, prefer side and bottom surfaces to flat ones pointing up, and aggregate gregariously in favorable microsites. Similarly most reef fish larvae seek healthy branching coral to recruit to, where they find the best food supply and hiding places from predators.

Hard corals, as well as a huge variety of soft corals, oysters, tunicates, and sponges are observed to settle preferentially on Biorock substrates compared to coral reef rock far away from Biorock structures. Coral larval settlement on limestone plates placed near to Biorock reefs, but not electrically connected to them, took place at rates several orders of magnitude higher than the highest values previously reported, suggesting that the larvae are attracted by the electrical fields around the structures. Biorock structures built in a severely polluted coral reef in Jamaica where no natural coral recruitment was taking place (due to severe algae overgrowth caused by nutrient eutrophication), were found to have 1.4 juvenile corals per square centimeter of Biorock surface. However the growth of these tiny juvenile corals, only about a millimeter across, was less than the growth of the underlying Biorock substrate, so they were enveloped by the Biorock mineral growth because they were too small to outgrow it. Slower growing Biorock structures show much higher rates of successful spontaneous hard coral recruitment. A small structure in Jamaica, about 2 meters across, received power for only a short time, growing a thin layer of Biorock material before the power was turned off. Half a year later this structure was found to be covered with hundreds of young corals of two species, each about 2 to 3 centimeters across, but there were no recruits at all on natural reef substrate nearby where dead corals were carpeted with fleshy algae. Structures receiving various levels of current in Ko Samui, Thailand showed an inverse relationship between electrical current and densities of spontaneously recruiting juvenile corals. The lowest structure receiving the lowest current was densely covered with spontaneously settling juvenile corals in about 6 months (Figure 7). Biorock reefs can be managed to greatly increase coral recruitment, but not under the same conditions that maximize structural strength or coral growth. By turning the power down or off during recruitment long enough for corals to attain sufficient size to outgrow Biorock minerals before the power is turned back up, great increases in natural coral settlement and growth might be achieved.

Figure 7. Spontaneously settling juvenile corals on an eight month old Biorock structure in Ko Samui, Thailand. Photo by Thomas Sarkisian

8.3. Fish and Invertebrate Recruitment

High recruitment and growth of all other attached reef organisms and fishes are also routinely observed on Biorock reefs, and further work is underway to see which organisms are most affected. Oysters of many species are observed to settle on the structures and reach adult sizes in less than six months. In particular juvenile reef fish are observed to settle on Biorock reefs at much higher rates than surrounding reefs, often appearing on Biorock reefs within a day of installation. While this could simply be due to preference for corals and vertical structures, it appears also to have an electrical field component because juvenile fish recruitment decreases after the power is turned off for a few weeks, while the corals become notably paler. When the power is turned back on juvenile fish return at high densities, and corals become visibly brighter and more fluorescent within a day. The mechanisms for this apparent attraction for fish are still unknown, because bony fish are regarded as having no electrical sense organs, unlike sharks and rays. Nurse sharks and sting rays have been observed in Biorock structures, but do not seem to be particularly attracted from great distances even though sharks can detect the electrical field of a flash light battery whose terminals are a thousand kilometers apart.

The spontaneous recruitment and steady increase of fish populations seen in time series photographs and videos is striking, especially when contrasted against adjacent concrete structures. No organism has been observed to obviously avoid Biorock reefs. Very rapid build up of fish populations have been observed, both juveniles and adults, including large schools of fish that hide in the structures by day and forage at night (such as grunts and snappers), fish that hide in the structure by night and forage in the day time, huge schools of permanent residents, primarily plankton-feeding fish like Chromis and Anthias, and large populations of mobile fish that pass through structures and seem to prefer to stay in them (including butterfly fish, triggerfish, sweetlips, emperors, fusiliers, groupers, surgeonfish, rabbitfish, parrotfish, jacks, puffers, cowfish, trumpet fish, razorfish, moray eels, and many others). In particular batfish and lionfish are very early recruits to Biorock structures and rapidly increase their populations, while barracudas frequently visit them. Clownfish are found in anemones on the structures, and cleaner wrasses and cleaner shrimp seem to prefer to set up cleaning stations in Biorock reefs, resulting in lines of fish queuing around waiting to be cleaned, making them ideal places to watch fish behavior. Gobies seem to prefer to establish burrows under the electrical cables, which might be due to electrical field effects in the surrounding water.

The Gondol Research Institute for Mariculture at Gerokgak, Buleleng, Bali, Indonesia, has released juvenile tiger and spotted groupers into Biorock projects. These were observed to grow rapidly in the structures for two years and then apparently migrated to deeper water, when they were replaced by spontaneously newly recruiting young groupers of other species. This suggests that fish hatchlings may have higher growth and survival in Biorock reefs than those that are released into open water or degraded reefs, and quantitative studies of growth and survival are needed. Fishermen could grow Biorock reefs, stock them with hatchlings, and get superior yields compared to those that are released into degraded reefs or open ocean waters. There are a wide range of methods for attracting fish and invertebrate larvae in the open ocean, using lights at night and fine nets. Fish larvae that are ready to metamorphose into juveniles could be collected and released into Biorock reefs, resulting in vastly greater larval survival and recruitment than happens naturally. Since most larvae are eaten when very small, enhanced survival and recruitment at this stage could make immense increases in standing stocks of many reef organisms. Much further work is needed in this direction.

8.4. Mariculture

Biorock reefs rapidly regenerate complex coral reef ecosystems, providing food and shelter for complex fish food chains much more like natural coral reefs than artificial reefs. Besides coral reef fish habitat restoration, Biorock technology has many other applications for mariculture. In waters too cold for corals, oyster reefs can be quickly grown, and in waters too muddy for either, fish habitat can still be grown. In almost any soft bottom habitat any hard structures create juvenile fish habitat and hiding places that greatly enhance their survival from predators. Since they can be built any shape or size, Biorock reefs can incorporate many more spaces and holes than natural reefs. Each species seeks holes of specific shapes and sizes, and since the size of the spaces can be customized to favor certain economically valuable species of fish and shellfish such as spiny lobster. Using open lattice frameworks of varied dimensions, species-specific spaces can be built in almost unlimited density, many times higher than occur in natural reefs, thus leading to greatly elevated standing stocks. For example, oysters frequently grow over each other, and the top oysters get most food, while the ones below get little. But Biorock oyster reefs can be stacked in many layers, with each layer fully exposed to phytoplankton and particulate organic matter food supplies. The only limitations are that the Biorock process requires a power supply, is most effective in seawater, is slower in brackish water, and normally does not work in fresh water. Biorock methods therefore have many potential uses in mariculture of many reef and non-reef organisms, including corals, fish, shellfish such as oysters and lobsters, and other invertebrates in many habitats.

Spiny lobsters and octopus seek holes of very specific size and dimensions, and their number limit the population size that can be supported. Lobster-sized crevices in Biorock reefs in Jamaica, Mexico, and Panama, were often crowded with up to dozens of spiny lobsters. Simple platform structures have greatly increased lobster populations and catches in Cuba. Especially crucial is shelter of juveniles in the seagrass stage, when lack of shelter causes heavy mortality. Multilayer Biorock structures might produce further increases, and might also grow barnacles and clam food for lobsters to eat on the surface of the Biorock substrate. Solar powered lobster habitat has been built for Kuna Indian fishermen in Panama, whose economy depends almost entirely on lobster exports, which are collapsing due to overharvesting and habitat degradation. Because the Kuna have preserved their mangroves, they have good sources of juveniles, so lobster habitat of the correct size in each habitat used by the lobsters at all stages of their life cycle might greatly increase sustainable catches.

To be widely implemented, this technology could allow fishermen to become reef gardeners rather than hunters. Management is needed in which fishermen control access to the resources they grow, just like farmers do, and will fail if there is open access and anybody can take it all. Community-based property rights are essential and western-style open entry fisheries would make such mariculture impossible. Pilot projects in Biorock fisheries restoration are underway in several community-based fisheries management areas in several countries, including Indonesia, Philippines, Thailand, and other countries. Clearly demarcated property rights also need to be linked to responsibility for maintenance. Cables must be checked for damage after storms and replaced if needed. Mariculture using Biorock technology should remove organisms that could overgrow more valuable species. Certain very fast-growing encrusting sponges can overgrow corals if not controlled periodically, and coral predators, including the crown of thorns starfish Acanthaster planci, Drupella and Coralliophila snails, and the fireworm Hermodice carunculata may be attracted to Biorock corals. To implement new technology, fishing communities must have access to loans for the materials needed. At present most subsistence fishing communities have little access to credit, and a micro-loan type credit system needs to be developed to allow them to greatly expand their knowledge, skills, and productivity in places where fisheries are now collapsing.

Biorock reef farming differs from conventional mariculture in several crucial aspects. First, the only external input is electrical energy, and no food is added. Second a large diversity of organisms is grown, a pluri-culture rather than a monoculture. Lack of genetic diversity in conventional mariculture promotes diseases and parasites from which the entire population can suddenly die, and can pollute local wild stocks with diseases and erode their genetic diversity. In contrast, because no food is added to Biorock reefs, a diverse food chain is maintained, avoiding the pollution problems from rotting food and excrement that have polluted surrounding waters around conventional fish mariculture operations in temperate waters. Biorock mariculture methods therefore avoid the genetic impoverishment, disease, parasite, and pollution problems that conventional mariculture has caused in many places. Coral reef ecosystems, because they require low nutrient waters, can be killed if conventional feed-dependent mariculture is started nearby, and these should be strictly banned in coral reef habitats. In contrast, Biorock reefs would enhance the local reefs, since they are often built over sand or rock next to natural coral reefs, increasing the area of coral habitat.

8.5. Shore Protection

Another benefit of Biorock reefs is that they can be specifically grown to protect coastlines from erosion while maintaining biodiversity, fisheries, and tourism benefits where natural reefs are damaged and degraded. A Biorock reef built in front of a severely eroding beach at Ihuru Island in the Maldives, where sand bags were being desperately piled along the shore to prevent trees and buildings from collapsing into the sea, acted to slow down the waves so their energy fell from erosional levels to depositional ones. As a result a 15 meter (50 foot) wide beach formed in around than three years, and this beach and the Biorock reef was undamaged by the 2004 Boxing Day Tsunami which passed right over the island. This shore protection reef is a tremendous tourism attraction right in front of the new beach, and cost less than a tenth of what a concrete seawall the same dimensions would have cost. A conventional seawall would have sped up sand erosion in front and provided no ecotourism, fisheries, or biodiversity benefits. The amount of electricity used to grow the reef is comparable to that used for the beach lights (which are low so as not to scare nesting turtles). Other shore line protection reef projects are being started in other low lying islands that are highly vulnerable to global sea level rise or waves from increased storm frequency and intensity that would be caused by global warming.

9. Conclusions

The decline of reef fisheries has accelerated in recent years, and will probably get much worse as global warming increases, threatening food security for some of the world’s poorest and most vulnerable people. High temperatures are already an imminent threat to the survival of coral reefs, reef fisheries, and the people who depend on them. So little reef area remains in good condition that conservation of remaining healthy sites alone is unlikely to avert a crisis in food supply. Coupled to increasing fishing pressure and rapidly diminishing coral reefs, sustainable reef fisheries will require large-scale coral reef fisheries habitat restoration and more sustainable management systems. Current economic forces indirectly reward reef destruction for short-term gain, and there are no funding or policy mechanisms now in place to reward those who grow reefs and increase sustainable fisheries yields. Reversing this trend is urgently needed because most fishing communities would adopt more productive methods if they had the knowledge and resources to do so. The techniques are at hand for large-scale improvements in productivity if the resources are made available, but fundamental changes in policy and mindset are needed, and the time remaining is very short for implementing them before fisheries decline further. Reef restoration can be a powerful tool in natural resources conservation and management, as well as in fisheries management if well planned and community driven. It may be the best hope for bringing back high densities of economically valuable species, such as groupers and lobsters, which have vanished or become very rare wherever the export market has penetrated or where local populations have grown faster than the capacity of the reef to feed them.

Glossary

Anode: A positively charged electrode.

Artisanal fisheries: Small-scale subsistence fishing, typical of poor coastal areas in the tropics where fishermen have little access to capital for equipment

Biorock process: Growth of solid limestone structures in the sea by electrolysis of sea water, causing naturally dissolved salts in sea water to precipitate.

Cathode: A negatively charged electrode.

Coral: Simple marine animals that grow limestone skeletons, and contain symbiotic algae that speed up their growth.

Coral reef: The solid framework built by corals which provides the habitat for fishes and invertebrates, the sand that builds beaches and islands, and a growing barrier that protects the shore from erosion.

Bleaching: Corals that turn pale or transparent due to loss of symbiotic algae. Bleaching is caused by environmental stress, and almost always this is due to excessive temperatures. Bleached corals are unable to grow or reproduce, and will die unless the stress is reduced. If the stress is mild or brief, corals can recover, but this can take months.

Electrode: An electrically charged metal terminal. The terminal can be either positively or negatively charged, and are called anodes or cathodes respectively

Electron: The unit of electricity, negatively charged

Electrolysis: Chemical reactions caused by electrical currents. When water undergoes electrolysis it is broken down to create hydrogen and hydroxyl ion at the cathode and oxygen and hydrogen ion at the anode. The cathode is therefore reducing and alkaline (high pH) while the anode is oxidizing and acidic (low pH)

Fish aggregating device (FAD): A floating structure designed to cast a shadow and attract pelagic fish. FADs can be made of logs, bamboo, coconut palm fronds, of from industrial materials.

Ion: A charged atom. Ions can be either positively or negatively charged. Water molecules which are made up of two hydrogen atoms joined to one oxygen atom, can be spilt to make two ions, a positively charged hydrogen ion (H⁺) and a negatively charged hydroxyl ion (OH^-). Because unlike charges attract and like charges repel, positively charged ions are attracted to negatively charged electrodes and repelled from positively charged electrodes, while negative ions have the opposite behavior

Invertebrate: An animal without a spinal cord or backbone, such as corals, sponges, worms, clams, lobsters, crabs, etc.

Larvae: The first stage of most marine organisms. Larvae are usually minute, free swimming or drifting in the open ocean, and look very different than adult organisms.

Limestone: A rock made up of calcium carbonate with minor amounts of magnesium. Coral skeletons and the shells of clams, snails, and most marine invertebrates are made up of limestone, as is the coral reef rock made up entirely by their remains. The Biorock process grows limestone mixed with magnesium minerals.

Metamorphosis: When larvae are sufficiently mature and find suitable habitat they change form (metamorphose) to become juveniles that look much more like a small adult than a larval form. The larvae are almost always pelagic, but the adult may be either pelagic or sessile.

Pelagic: Free swimming animals, like fishes.

pH:A measure of acidity. Low pH indicates high hydrogen ion concentration and acid conditions, while high pH indicates high hydroxyl ion concentration and alkaline conditions

Photophilic: Attracted to light

Photophobic: Repelled by light, seek dark places

Plankton: Small marine organisms that drift with the currents like the larvae of most fish and invertebrates

Recruitment: Larvae that choose a suitable habitat to metamorphose into juveniles are said to recruit to the habitat they settle in.

Sessile: Non-mobile organisms, attached to a hard surface. They include corals, sponges, clams, and many invertebrates. Sessile organisms usually have free swimming pelagic larvae that live in the open ocean before they metamorphose and settle.

Symbiotic: Organisms living together in a way that both partners benefit. Corals are a symbiotic partnership between the coral animal and microscopic algae called zooxanthellae. When the symbiosis is disrupted by loss of the algae the coral becomes bleached, stops growing and reproducing, and may die.

Zooxanthella (plural zooxanthellae): Microscopic algae that live symbiotically inside coral tissue and provide the coral with its color and ability to grow its skeleton.

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Sale P. (Ed.) (2002). Coral Reef Fishes: Diversity and Dynamics in a Complex Ecosystem, Academic Press, 724 pp [Collection of scientific papers on all aspects of coral reef fish ecology]

Suman D. (1988). Fisheries Technologies for Developing Countries, National Academies Press, Washington, DC. [A very comprehensive study of methods that can be used to increase artisanal fish catches. The author now feels guilty that the more efficient methods explained may have increased overharvesting]

Walley C.J. (2004). Rough Waters: Nature and Development in an East African Marine Park, 308p, Princeton University Press [A sociological study of the conflicts between top down resource management efforts and fishing communities]

Biographical Sketches

Dr. Tom Goreau, President of the Global Coral Reef Alliance, a non-profit organization for coral reef protection and sustainable management, has dived longer and in more coral reefs around the world than any scientist. His father was the world’s first diving marine scientist, and he grew up swimming in coral reefs as soon as he could walk. He was previously Senior Scientific Affairs Officer at the United Nations Centre for Science and Technology for Development, in charge of global climate change and biodiversity issues. He has published around 200 papers in all areas of coral reef ecology, and on global climate change, the global carbon cycle, changes in global ocean circulation, tropical deforestation and reforestation, microbiology, marine diseases, soil science, atmospheric chemistry, community-based coastal zone management, mathematical modeling of climate records, visualizing turbulent flow around marine organisms, scientific photography, and other fields. He developed the method to predict the location, timing, and severity of coral bleaching from satellite data with Ray Hayes. He holds patents with Wolf Hilbertz for new methods for preserving coral reefs from global warming and pollution, restoring marine ecosystems, shore protection, mariculture, and non-toxic methods of preserving wood from marine boring organisms, termites, rot, and fire, in order to increase the lifetime of wood and decrease logging. In 1998 he and Wolf Hilbertz were awarded the Theodore M. Sperry Award for Pioneers and Innovators, the top award of the Society for Ecological Restoration. Dr. Goreau led developing country NGO efforts in marine and climate issues at the United Nations Conference on Environment and Development (Rio de Janeiro, 1992), the UN Summits on Development of Small Island Developing States (Barbados, 1994, Mauritius, 2005), and the UN World Summit on Sustainable Development (Johannesburg, 2002). Dr, Goreau works with tropical fishing communities around the world to restore their coral reefs and fisheries, especially the Kuna Indians of Panama, the only Native people of the Americas who have preserved their cultural and political independence. He is also a hereditary leader of the Yolngu Dhuwa Aboriginal clan of Arnhem Land, Australia, that preserves the oldest creation myth in the world. Of Panamanian origin, he was educated in Jamaican primary and secondary schools, at MIT (B.Sc in Planetary Physics), Caltech (M.Sc in Planetary Astronomy), Yale, Woods Hole Oceanographic Institution, and Harvard (Ph.D. in Biogeochemistry), and is a certified nuisance crocodile remover. 

Wolf Hilbertz studied architecture and landscape architecture in Berlin, Germany and at the University of Michigan, USA. He practiced in design offices in both countries and taught/researched at Southern University, a black college in Louisiana, The University of Texas, McGill University, and the Academy of Fine Arts at Bremen. The inventor of the terms Cybertecture (structures that grow and heal themselves) and Seascaping (marine landscaping), he has long been a pioneer in innovative new methods to grow structures, starting with computer controlled spray nozzles to grow buildings out of ice in North Dakota winters. He invented the technology of mineral accretion in seawater in the early 1970s to produce prefabricated limestone building materials in the sea. He has collaborated with Thomas Goreau since the 1980s applying Biorock technology to solve pressing ecological and socio-economic issues globally, and is generally regarded as the guru of the emerging field of seascape architecture. He is a recipient of the Theodore M. Sperry Award for Pioneers and Innovators in Restoration, the top accolade of the Society for Ecological Restoration.

To cite this chapter

Thomas J. Goreau,Raymond L. Hayes ,(2008), Reef Restoration as a Fisheries Management Tool, in Fisheries and Aquaculture, [Ed. Patrick Safran], in Encyclopedia of Life Support Systems (EOLSS), Developed under the Auspices of the UNESCO, Eolss Publishers, Oxford ,UK, [http://www.eolss.net]