- Over 200 artificial reefs were installed at Worli Koliwada in Mumbai with an aim to boost fish populations and support fisher livelihoods amid the impacts of infrastructure projects.
- Artificial reefs are used to enhance the growth of marine floral and faunal benthic communities, simulating natural settings to promote fish aggregations and provide breeding or feeding opportunities.
- While artificial reefs have shown success in enhancing marine habitats and boosting fish catches in various Indian states, there are concerns about their long-term ecological impacts, such as potential pollution and invasive species proliferation.
Mumbai got its first set of over 200 artificial reefs in February this year, at Worli Koliwada. These artificial structures mimic natural reefs and in Mumbai, they are aimed at countering the declining fish catch and improving sustainability of fishing as a livelihood, amid the impact of infrastructure projects. While the use of artificial reefs has seen success in many projects around India, some scientists have expressed uncertainty about their long-term impact.
“Overall, the deployment of artificial reefs has been a success story because, unlike many other conservation projects, it not only slows down the damage caused to fish habitation but also grows it,” says Punit Dhandhania, one of the founders of the Puducherry-headquartered NGO Kuddle Life Foundation that led this project, funded by the RPG Foundation. Kuddle Life Foundation has been actively deploying these artificial reefs in Puducherry for the last four years.
The use of artificial reefs is also being promoted by the government of India, as a unified initiative for the country, under the Prime Minister’s Matsya Sampada Yojana (PMMSY) scheme. The Union Department of Fisheries announced, in August 2023, the deployment of artificial reefs across 3,477 fishing villages across India, including in Maharashtra, over the next two to three years. The reef installation programme under this nation-wide initiative is led by the Central Marine Fisheries Research Institute (CMFRI), headquartered in Kochi, Kerala and intended to promote sustainable fisheries and livelihoods, especially for small fishers
“We need artificial reefs not just to grow the fish population in our waters but also to mitigate the growing number of cyclones and typhoons caused by climate change,” says Hussain Mohammad Kasim, former principal scientist of CMFRI and one of the pioneers of the artificial reef project in India. He has been working on these for the last three decades.
In Mumbai, the recent deployment of artificial reefs by Kuddle Foundation is expected to bring some relief to fishers, particularly artisanal fishers, that are affected by the infrastructure projects through the city’s waters. From the Bandra-Worli Sea Link, which was operational in 2009-10 to the Mumbai Trans Harbour Link in 2024, and now the partially operational and under-construction Coastal Road, infrastructure projects in Mumbai’s sea have adversely affected the livelihood of the city’s fishing communities.
Dipak Patil, a 57-year-old fisherman, is one of the 5,000 fishers of Worli Koliwada who has witnessed this impact. His family has been in the fishing business for four generations. He recalls how, back in the 1980s, it was easy to get fish on the shore. But now, on most days, he and others have to venture at least two to three kms away to catch fish. Even then, with the noise, pathway closures and waste generated by the coastal road construction, the catch has become scarce. “There are also days when we get 60% garbage in our nets and just 40% fish, especially during high tide,” he says.
A 2023 Tata Institute of Social Sciences study commissioned by the Brihanmumbai Municipal Corporation, found that non-mechanised boat owners’ daily catch fell from 14 kgs per day before October 2018, when work on the coastal bridge began, to seven kgs afterward. The report was compiled based on responses from 680 project-affected fishers (PAF). Of these, 560 belonged to Worli Koliwada, and 120 were from Lotus Jetty (Haji Ali).
Boosting fish population and biodiversity
Artificial reefs are used to enhance the growth of marine floral and faunal benthic communities, simulating natural settings to promote fish aggregations and provide breeding/feeding opportunities, according to a 20203 CMFRI report. Fishers can then access the areas around these structures to catch the fish growing here.
Fishes are attracted to any object in the sea, including the submerged pillars of bridges or boat bottoms. According to Kasim, hundreds of years ago, fishers used huge logs of wood to attract fish. However, these degraded quickly. But when specially designed concrete structures with holes and crevices for fish to reside are placed at the right site, they can last for years. Over time, typically three to six months, depending on sea conditions, a biofilm grows on these structures, attracting larvae, plankton and other organisms. This, in turn, attracts small organisms and fishes, creating a thriving marine habitat. Kasim likens it to creating a fully stocked kitchen underwater, where fish of all sizes come to dine.
In Puducherry, the fishers of Chinna Mudaliyar Chavadi village have benefited from the artificial reef deployed near their shore about a year ago by the Kuddle Life Foundation. Previously, they had to travel at least 10 to 15 kms away from the shore to get a good yield. But since then, they have been getting a good amount of kingfish, tuna, red snappers, crab, prawns, squid, and sometimes even octopus around the artificial reefs, which are placed just 2.5 kms away from the shore. Fisherman Moorthy, 37, recalls that the last time they found fish this close to the shore was when he fished with his father almost two decades ago. Over time, the number of fish dwindled and they started sailing farther away, at least 15 kms off the shore. But not anymore, as fish are back in closer waters, thanks to the artificial reefs. These reefs have also helped Moorthy and other fishers from the village save a significant amount on fuel costs. They now pay Rs. 250 for fuel to travel the distance of 2.5 kms, compared to the Rs. 1,500 they paid to travel 15 kms. “More savings mean more profit,” says Prabhas, 29, another fisherman from the village. Additionally, most trips around the reef are productive and the fishing community is sure to find a good catch.
Similar artificial reef installations have yielded positive results in Kerala, Andhra Pradesh and Gujarat as well over the past three decades, highlights the CMFRI report. One of the biggest success stories is in Tamil Nadu. Since 2006, the state’s fisheries department has deployed artificial reefs in 125 coastal sites spread across ten districts along the coast. The International Fund for Agricultural Development-assisted Post 19 Tsunami Sustainable Livelihoods Programme (PTSLP) of Tamil Nadu Corporation for Development of Women (TNCDW) has also deployed artificial reefs along the Tamil Nadu coast, with 18 sites by CMFRI and 42 by the National Institute of Ocean Technology (NIOT). Other NGOs and agencies have deployed artificial reefs together in 22 other sites in the state from 2000 to 2020, the CMFRI report underlines.
Read more: Artificial reefs breathe new life for Tamil Nadu’s fishing communities
Artificial reefs have also been known to increase the biodiversity of a region, especially in bare-bottom areas that do not naturally have structures like coral or rocky reefs. The hard surface of the concrete reefs promotes the growth of algae, other plants, and invertebrates like corals, molluscs, or crustaceans, providing shelter to different fishes in different life stages. ARs may function as adult or sub-adult habitats for various species, promoting biodiversity and recreational diving for tourism growth, explains Kasim, who is one of the authors of the CMFRI report.
Moreover, artificial reefs increase the surface area of the sea floor, as Kasim explained. While a ten-metre wall constructed on the sea bed would lose that much area of the floor, artificial reefs, depending on their length, help gain sea floor area. “More area means more organisms,” says Kasim.
Additionally, artificial reefs have proved useful in removing oil spillage from the sea. In Gulf countries, artificial reefs are placed near oil refineries. Some algae, larvae, and fishes grown on these structures could absorb oil particles and clean the waters. Similarly, artificial reefs can be used to control sea pollution in an area, as some marine organisms that grow on the reefs are known to have qualities that can clean the waters of certain polluting materials. However, such projects haven’t been initiated in India yet, says Kasim.
Kasim claims that artificial reefs can also absorb the impact of cyclones and tsunamis and mitigate their impact on land.
Read more: Coral transplantation helps, but not the only solution
Concrete concerns
While India is ambitious in its pursuit of AR, global evidence suggests that such initiatives also require careful planning. French scientist Katell Guizien, a fellow of the National Centre for Scientific Research in France, has dived into and evaluated artificial reef sites in the North Western Mediterranean Sea. Her research aimed to examine the reefs deployed in the sea over the last ten to thirty years and their connection with the natural habitat of those waters. According to French law, these reefs must be removed when the stipulated time is over, but many have been left on the ocean floor due to the dissolution of the deploying companies.
While talking to Mongabay India, Guizien says that the study was prompted after rare species of benthic invertebrates (such as corals and other invertebrates that inhabit the benthic zone, the ecological region at the lowest level of a body of water) were found on wind turbines amidst the seas while the government planned to decommission them. This led scientists to investigate whether the artificial structures left at sea for extended periods would alter species’ functional connectivity.
She concluded that neither the age nor the shape, but the location, definitely played a role in colonisation. In some reefs, she found a variety of species of benthic invertebrates, but in others, only one species was present. This, she thinks, could be problematic. Some benthic invertebrates reproduce faster than others, leaving no space for others to thrive. They can quickly dominate the reef environment and spread across the natural environment, negatively impacting the biodiversity of the sea. “Also, one will never find just one kind of benthic invertebrates in any natural environment,” says Guizien to Mongabay India.
Additionally, Guizien’s research revealed that not all artificial reefs had matured even after 30 years, indicating that they had not colonised as much as natural reefs. Another concern is that artificial reefs could become breeding sites for non-native, invasive corals and fishes, potentially harming local ecology. Concrete, while accepted as one of the best materials for artificial reefs globally, still pollutes the ocean to some extent by releasing toxins.
Furthermore, artificial reefs have an expiry date and may lose efficacy after three decades, potentially becoming empty structures. However, uncertainty remains as not enough research has been conducted in this area, says Punit Dhandhania.
Artificial reefs also have certain limitations. They require a sandy surface and should not disturb local habitats. Rapid movement in the ocean can cause them to sink into the sand or damage corals. Additionally, these structures need sunlight for biofilms to form, making them unsuitable for deployment in deep-sea areas. They may also obstruct trawlers, posing challenges primarily for small fishermen, says Kasim.
However, unlike other countries, such as France, which mandate the removal of artificial reefs after a few years, Kasim believes that those in Indian waters shouldn’t be removed.
Banner image: Artificial reefs being installed. In 2023, the union government announced the deployment of artificial reefs across India’s coastline to boost the fish population. Image courtesy of the Kuddle Life Foundation.
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