Persistent Demand and Impacts on the Sea Cucumber Industry
The continual demand for sea cucumber products in Asian, notably Chinese, markets has significantly boosted the economies of tropical coastal communities. These sea creatures are primarily harvested for a high-end dried food product known as beche-de-mar. Yet, dwindling wild populations due to excessive fishing have spurred interest in aquaculture as a way to fulfill ongoing demand, secure more stable income sources, and broaden economic opportunities.
Aquaculture Techniques
Key methods for farming sea cucumbers include pond farming, pen culture, sea ranching, and tank culture. Employing larger juveniles in the first three methods tends to enhance survival rates, albeit at a higher cost at the nursery stage. Juveniles that exceed 20 grams are typically resilient against predators like crabs. In these settings, apart from tank culture, juveniles generally do not need additional feeding because they sustain themselves by consuming algae and aquatic invertebrates found on the ocean floor, which also helps to maintain water quality. Optimal stocking density should be kept below 200 g/m², as exceeding this threshold can stall growth.
Pond Farming
Typically located in the intertidal zone near shorelines, pond farms utilize tidal movements to facilitate seawater exchange, controlled by managing sluice gates. These ponds may be converted from old shrimp or crab farms or newly created with appropriate substrates. Sea cucumbers can also be cultivated alongside other species such as shrimp, which helps enhance the pond environment by consuming sediment and organic remnants.
Tropical species are usually farmed in ponds with water depths between 0.8 to 1.5 meters. In regions like southern China, Holothuria scabra are cultivated together with pearl oysters and groupers in extensive earthen ponds. For temperate species, optimal pond conditions include proximity to the low tide mark to utilize gravity-fed seawater, low pollution levels, salinity between 28 and 31, sandy or muddy bottoms, depths over 2 meters, and structural protection against severe weather.
Pond preparation involves drying, predator removal, sediment tilling, setting up nets at sluice gates to keep out predators and prevent escapes, liming the pond, and refilling with seawater for about a week before adding juveniles.
Challenges with pond farming include managing the impacts of heavy rainfall and high temperatures, which sea cucumbers are sensitive to. The lengthy culture period can also inflate costs related to pond leasing and labor, especially during the unpredictable rainy season.
Sea Ranching
In sea ranching, hatchery-raised juveniles are released into natural, unenclosed marine habitats to grow until they are ready for harvest. Effective sea ranching relies on selecting sites that are shielded from adverse natural conditions and theft, have healthy ecosystems with existing wild sea cucumber populations and seagrass beds, and receive robust community and governmental support.
This method requires minimal labor for upkeep but typically sees lower survival rates than pen or pond farming methods. Additionally, the lack of clearly defined property rights in sea ranching areas can lead to significant issues with poaching.