Solar-Powered Cages Enable Pearl Spot Farming in Remote Mangroves
A case study published in Aquaculture Science and Management demonstrates that a solar-powered, off-grid cage culture system can successfully support the semi-intensive farming of pearl spot (Etroplus suratensis) in remote mangrove habitats. The research, conducted at Nedungolam in Kollam district, Kerala, India, evaluates the technical feasibility and environmental sustainability of using renewable energy to maintain critical aquaculture operations in areas lacking reliable grid electricity. The study highlights that such a system can effectively mitigate nocturnal oxygen stress and enable autonomous farm operation, offering a potential model for sustainable aquaculture in energy-deficient coastal ecosystems.
The primary challenge addressed by the study is the widespread underutilization of inland water bodies in remote regions due to the absence of continuous power supply. In semi-intensive and intensive culture systems, reliable electricity is essential for water pumping and aeration, which are critical for maintaining adequate dissolved oxygen levels. When dissolved oxygen drops below 1 mg L⁻¹, fish growth slows and mortality can occur due to prolonged exposure to low oxygen conditions. Consequently, many farmers in these isolated areas are unable to utilize their available water resources for aquaculture, resulting in lost production opportunities and income. Solar-based cage culture offers a sustainable alternative by integrating renewable energy technology with aquatic food production.
The experimental setup involved a 3 kW photovoltaic system deployed at a mangrove island site with a 1.5-acre water spread area. The site, located at coordinates 8º50’28.79“N, 76º40’43.30“E, had no direct hydrological connection to the sea but maintained brackish water conditions with salinity ranging from 5 to 15 ppt. The solar system was designed to support four 90W aeration pumps, three CCTV cameras, three LED lamps, and ten electronic accessories for wireless control and monitoring. The system operated from 6 PM to 6 AM, utilizing lithium-ion batteries to store daytime solar energy for overnight discharge. This energy-autonomous approach was managed by Adrak Ventures, with engineering support from Green Turn Energy and module design by the Centre of Excellence in Advanced Materials at Cochin University of Science and Technology.
For the culture experiment, 4,500 pearl spot fingerlings were acclimated for 15 days in high-density polyethylene (HDPE) hapas before being stocked into nine floating cages. Each cage had a volume of 10 m³ and was constructed with 210D nylon knotless nets of 10 mm mesh size. The stocking density was set at 50 fish per m³, resulting in 500 fingerlings per cage. The fish, which had an initial average weight of 4.19 ± 0.81 g and length of 5.89 ± 0.81 cm, were reared under semi-intensive conditions for a 214-day period, approximately seven months. Feeding rates were adjusted from 3 to 5% of body weight initially, increasing to 7–9% as the fish grew larger, using commercial dry pellets provided by Growel Feeds, India.
The solar power system demonstrated sufficient capacity to meet the energy demands of the farm, with an estimated daily energy generation of about 12 kWh. The total daily power consumption of the floating solar panels was recorded at 5.7 kWh, with the aeration pumps accounting for the highest consumption at 4,800 Wh. The performance of the 3 kWp solar PV system ensured that nighttime dissolved oxygen levels were maintained above the critical threshold of 5 mg L⁻¹ throughout the culture period. The aeration units, powered by the solar-charged battery bank, operated continuously during nocturnal hours, preventing oxygen depletion even under high biomass conditions. This indicates that the installed PV-battery system provided adequate energy storage and discharge capacity to support the aeration demands of semi-intensive cage culture.
Water quality parameters in the solar-aerated test units showed statistically significant improvements compared to the non-aerated control units. Dissolved oxygen concentrations in the test cages ranged from 12.45 to 13.66 mg L⁻¹, significantly higher than the 2.63 to 3.42 mg L⁻¹ observed in the control units. The elevated oxygen levels in the test units likely reflect localized oxygen supersaturation resulting from continuous aeration and enhanced water circulation. Additionally, the test units maintained substantially lower ammonia (NH₃) concentrations, ranging from 0.00 to 0.13 mg L⁻¹, compared to 0.53 to 1.01 mg L⁻¹ in the control units. The presence of measurable nitrite and nitrate levels in the test units suggests active nitrification, mediated by a nitrifying bacterial consortium applied monthly to both ponds, which converts toxic ammonia into less harmful intermediates.
Sediment quality and plankton abundance also indicated a healthier ecosystem in the solar-powered system. The sediment redox potential (Eh) in the test units was less negative, ranging from −150 to −186 mV, compared to an average of −297.66 mV in the control units, indicating improved sediment conditions. Phytoplankton and zooplankton abundances were higher in the test units, with phytoplankton counts reaching a peak of 76 ± 0.81 cells mL⁻¹ and zooplankton counts up to 8.33 ± 0.47 organisms mL⁻¹. These balanced planktonic communities provided natural food resources and reflected stable ecological functioning within the solar-powered environment, where continuous aeration helped prevent bloom formation and maintained adequate oxygenation.
The growth performance of the pearl spot in the solar-powered cages was satisfactory, with fish attaining an average final weight of 205.07 ± 1.25 g after 214 days. The average daily weight gain was 1.14 ± 0.11 g, and the specific growth rate was 2.17 ± 0.03. The feed conversion ratio was recorded at 1.80 ± 0.04, indicating efficient feed utilization. The total biomass yield was 80.5 ± 1.09 kg per cage, translating to 8.05 kg per m³. Although a 22% mortality rate was observed in the third month of culture in three cages due to an Argulus sp. infestation, the overall growth and survival rates demonstrated the species’ ability to thrive in the solar-powered system. The affected fish were treated with Doramectin and Ivermectin, and the outbreak was effectively controlled.
The economic analysis of the project revealed that the total installation cost for the solar power system, including engineering design, material supply, and commissioning, was Rs. 6,09,386 (approximately 6,816 USD). This cost-benefit assessment suggests that solar energy is a cost-effective solution for remote aquaculture operations, offering long-term benefits such as zero fuel consumption and low maintenance. The productivity level of 8.05 kg per m³ is comparable to traditional fish ponds with semi-intensive production, providing a viable option for farmers to increase their production capacity in isolated locations. The integration of solar energy into cage culture thus presents a sustainable and environmentally friendly alternative to conventional energy sources like diesel generators.
The study acknowledges several limitations that must be considered when interpreting the results. As a demonstration trial conducted at a single site over a single production cycle, the findings may not be universally applicable to all farming conditions. The absence of a fish-stocked non-aerated control group limits the direct comparison of the solar-powered aeration system’s specific effects on fish growth and survival. Furthermore, the Argulus infestation and the subsequent antiparasitic treatments may have influenced the growth and survival data, and the potential ecological impacts of these treatments on the surrounding mangrove ecosystem were not assessed. The economic analysis was also limited to a simple cost-benefit assessment without a detailed techno-economic evaluation.
Despite these limitations, the study provides valuable insights into the potential of renewable energy technologies in aquaculture. The successful implementation of the solar-powered cage culture system demonstrates that integrating solar energy can effectively address power shortages in remote coastal and island areas. This approach promotes eco-friendly and energy-resilient fish farming, contributing to the long-term sustainability of aquaculture operations. The findings support the wider adoption of renewable energy in aquaculture to enhance productivity, environmental stewardship, and economic sustainability in energy-deficient regions.
Future research should focus on optimizing system design, incorporating hybrid energy sources such as solar-wind combinations, and integrating automation and data-driven management tools. These advancements could further improve performance and scalability in various aquaculture environments. By addressing the energy constraints of remote aquaculture, solar-powered cage culture offers a promising pathway for sustainable food production and livelihood enhancement in off-grid communities.
Subject of Research: Performance of a solar-powered off-grid cage culture system for Etroplus suratensis in remote mangrove habitats.
Article Title: Sustainable off-grid cage culture: assessing the performance of a functional, energy-autonomous, solar-powered farming model for Etroplus suratensis (Bloch, 1790) in remote mangrove habitats
Article References: Kunjiraman, S., Akshay, P. S., Kannan, M. S. A., Sarasan, M., Antony, A., Vivek, K., Joseph, V., Singh, I. S. B., & Puthumana, J. (2026). Sustainable off-grid cage culture: assessing the performance of a functional, energy-autonomous, solar-powered farming model for Etroplus suratensis (Bloch, 1790) in remote mangrove habitats. Aquaculture Science and Management, 3(1), Article 22. https://doi.org/10.1186/s44365-026-00050-w
Image Credits: AI Generated
DOI: 10.1186/s44365-026-00050-w
Keywords: solar aquaculture, cage culture, Etroplus suratensis, mangrove habitats, off-grid energy, dissolved oxygen, sustainable farming, renewable energy, water quality, fish farming, Sustainable, off-grid
News Source: Alan Morgan. (November 9, 2026). Solar-Powered Cages Enable Pearl Spot Farming in Remote Mangroves. Scienmag.
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