Shell Nurse reef in La Paz, a Japanese model for restoring the Gulf of California

The Shell Nurse artificial reef is transforming marine life in San Juan de la Costa, Baja California Sur and represents a step towards creating the first marine ranch in Mexico.
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The waters off San Juan de la Costa, in Baja California Sur, went from being a sandy bottom to an oasis of marine life due to the placement of the Shell Nurse artificial reef, the first of its kind off the Japanese coast, which represents an advance for the creation of the first marine ranch in Mexico.

These reefs were planted to solve an environmental problem: the excess of shells generated by mollusc fishing. But it has also resulted in a method for restoring marine ecosystems in sandy deserts.

The reef is an example of what in Japan is called satoumi, an approach to coastal management where human interaction with nature has increased biodiversity and productivity. The term is composed of the words “sato”, which means “the area where people live”, and “umi”, “the sea”, meaning a socio-ecological system characterized by the interaction between human life and the coastal ecosystem.

“Mollusc fishing is one of the main activities in Baja California Sur, but it also generates organic waste, specifically, shells that accumulated and were becoming an environmental problem. The Japanese consultancy firm Overseas Agri-fisheries (OAFIC) suggests that the state government address the problem immediately,” says Viridiana Zepeda of the Mexican Institute for Sustainable Fisheries and Aquaculture Research (Imipas).

To address this situation, OAFIC contacted the Japan International Cooperation Agency (JICA) and it hired the company Value Frontier, an expert consultant in sustainable solutions who proposed hiring the company Ocean Construction (OC), an expert in artificial reefs to make use of shells that would no longer have an impact on the environment.

“The plus of OC is that it integrates shells into the structure of the reef because through their research and their experience of more than 40 years in Japan, they have realized that fish have a greater affinity for congregating in shell areas than in any other inorganic material that artificial reefs may be made of,” Zepeda said.

In 2017, JICA authorized a fund of one million dollars for the project and by 2023, after testing, monitoring, designing the project and obtaining environmental impact authorization from the Ministry of Environment and Natural Resources (Semarnat), a pilot test was implemented in La Paz Bay.

The project coined the term satoumi at the request of JICA and also in May 2023, the Satoumi Council was installed, consisting of government bodies (Semarnat, Conapesca, Imipas, Sepuimm, Sepada), civil society organizations (Sustainable Northwest), educational institutions (UABCS) and fishing cooperatives (Fedecoop Centro), which is responsible for maintaining and operating the reef.

The company OC built the structures made of concrete, steel and polymer in Japan, and later they were imported to La Paz, where in a first phase, in May 2023, the fishermen provided shells to fill the 200 structures that were placed on the seabed: a mountain of 150 structures and another of 50.

Interiors 900x600.jpgFishermen place the structures on the seabed in front of San Juan de la Costa. Source: Marco Antonio Medina López

Interiors 900x600 (1) .jpgConcrete, steel and polymer structures created by Ocean Construction and filled with shells in La Paz, installed on the seabed. Source: Marco Antonio Medina López

In August of the same year, the first underwater monitoring was carried out by divers from the Autonomous University of Baja California Sur (UABCS) and the company OC, which showed an increase in biodiversity.

“Obviously, in the biological part, we know that the longer it passes, the more volume there will be until it reaches a limit where it remains more or less constant.

We don't know right now until when, but we do see a significant increase,” said Marco Medina, a researcher at the UABCS and responsible for monitoring the reef.

One year after its placement, abundance monitoring showed that there were 24,284 organisms of 35 species, of which 14 were of commercial importance, such as cochito, cabrilla, horse mackerel, yellow snapper, parakeet fish, and others. While approximately 17 to 20 species are permanently maintained on the reef.

The presence of horse mackerel has also been observed on the periphery of artificial reefs, suggesting an increase in nearby trophic levels. However, more time is needed to confirm clear trends, said Yutzín Jiménez, a doctoral student at the Interdisciplinary Center for Marine Sciences and a diver who monitors the diversity and abundance of invertebrate fish.

Interiors 900x600 (2) .jpgShell Nurse artificial reef of 150 structures on the seabed in San Juan de la Costa. Source: Marco Antonio Medina López

In April 2024, the state government received funding from the Inter-American Development Bank for research to determine if the reef attracts fish or if it is a biomass generator.

Throughout this process, they have also realized that it is necessary to protect the reef, so they are in the process of applying for a fishing refuge area in the area.

“We are in the process of applying to Conapesca for the establishment of a small area of fishing refuge to specifically protect the reef; we are still doing research on it, I tell you that it is a pilot project so we need to keep it intact to continue monitoring it,” Zepeda said.

In addition to increasing biodiversity, artificial reefs provide species with areas where they can shelter from predation and feeding areas. According to Zepeda, this contributes to ecosystem resilience, improves overall health and also has a positive impact on fishing communities.

“We know that across the country, the reduction of fishing is a problem. It faces very important challenges such as overfishing, pollution of the area, degradation of ecosystems, scarcity. These challenges not only affect the local economy but also impact the food security of the communities that depend on this fishery. We are attacking the problem of shell accumulation, but with these reefs we also have alternative positive impacts that will benefit communities,” Zepeda said.

According to a statement from the State Government, the reef will benefit 898 fishermen belonging to the Dos Mares and Fedecoop cooperatives in the medium term, who catch fish in the Gulf of California.

In addition, with the monitoring results obtained from the first reef, the Satoumi council placed a second one with 83 structures submerged in the same area 30 meters deep on December 1, 2024. This also involved the collaboration of all sectors: academia, government, civil society organizations and fishermen.

These two reefs make up a larger project that the Satoumi Council aspires to achieve in Mexico: marine ranches, understood as areas designed to create varied spaces based on the arrangement and distribution of shell reefs, where species find sufficient and adequate habitat for their permanence. In this way, dynamic and productive marine spaces are created.

WhatsApp Image 2024-12-10 at 5.17.48 PM.jpegSource: Alejandro Robles

Written by

Daniela Reyes

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