Sponge aquaculture, often referred to as mariculture, is the controlled farming of marine sponges primarily for commercial purposes, such as producing bath sponges or sources for bioactive compounds. This practice developed as a response to historical overharvesting, which depleted natural stocks worldwide. Cultivation attempts date back to the late 19th century, recognizing the remarkable regenerative ability of these organisms to regrow from small fragments. Sponge farming provides a sustainable alternative to wild collection, ensuring a consistent supply while reducing pressure on natural marine ecosystems.
Selecting Commercial Species and Optimal Sites
The initial step involves identifying suitable species and locating an optimal cultivation site. For commercial bath sponge production, species from the genera Spongia and Hippospongia are selected due to their desirable texture, large size, and natural resilience. These species possess a skeletal structure composed of soft spongin fibers, which provides the quality consumers expect.
Successful growth depends on careful site selection and specific environmental conditions. Sponges thrive best in areas with low pollution and stable water quality, away from damaging freshwater runoff. The site needs moderate water movement to ensure a constant supply of food particles and oxygen, which the sessile sponges filter. Optimal locations are shallow, nutrient-rich lagoonal waters in tropical or subtropical regions, where stable temperatures promote faster growth.
Core Cultivation Techniques
The physical process begins with fragmentation, where a parent sponge (broodstock) is prepared for propagation. The tissue is cut into smaller, viable pieces, called explants, using a sharp knife to ensure a clean cut. To maximize survival, fragments are typically cut into square, oval, or triangular shapes, generally weighing 150 to 300 grams wet-weight.
Explants are secured using one of two primary methods: line culture or tray culture. In the line culture method, a nylon line is threaded through the fragment using a needle, and the ends are looped onto a heavier, submerged horizontal growing line. This method is favored because it can be managed from the surface in shallow water without specialized diving equipment.
The second method involves tray or raft culture, where fragments are placed onto nets or hanging trays suspended from floating rafts. This technique is effective in calmer waters, and the rafts maintain the sponges at an appropriate depth for optimal nutrient exposure. Regardless of the attachment method, the lines or rafts are deployed with adequate spacing to allow for good water circulation and maximize the delivery of food and oxygen.
Long-Term Management and Collection
Sponge cultivation requires continuous monitoring and maintenance. Farmers must regularly inspect the lines and explants for fouling organisms, such as algae and weeds, which compete for nutrients and restrict water flow. Periodic checks are also necessary to monitor for potential predators, including certain species of starfish or snails that feed on sponge tissue.
Sponges grow relatively slowly, typically requiring two to five years to reach commercial size (around 800 grams). The harvesting process is selective, involving cutting the sponge at its base while leaving a small portion, or “root,” attached to the substrate to encourage regeneration. This practice is sustainable, as the remaining tissue can regrow into a new sponge, providing a continuous yield.
After collection, the sponges undergo a multi-step post-harvest process to prepare them for market.
Post-Harvest Processing
Initially, the sponges are cleaned to remove the dark outer skin, debris, and internal organic matter, often by being left to cure on the deck for several days under wet burlap. The material is then squeezed and pounded to remove the non-skeletal tissue, leaving only the soft, fibrous skeleton. The final steps involve rinsing, drying, and treating the sponges in a weak acid solution to lighten their color and remove residual impurities before they are trimmed for sale.