A Comprehensive Analysis of Key Points in Sea Cucumber Aquaculture Technology
The "Supplements to the Compendium of Materia Medica" (Bencao Gangmu Shiyi) records the following about sea cucumber: "The sea cucumber has a dark brown body color, tender flesh and many spines. Not only is its quality the best, but its medicinal nature is sweet and warm and non-toxic, with effects such as tonifying kidney yin, generating blood vessels, and treating dysentery and ulcers. Because its medicinal nature is warming and tonifying, it is comparable to ginseng, hence the name sea cucumber (haishen)."
Since sea cucumbers generally require a growth period of 3-5 years, and most grow in deep seas at depths from 5 or 6 m to 20 m, their growth cycle is long and harvesting is inconvenient, so the annual harvest volume falls far short of market demand.
In recent years, China's artificial sea cucumber seedling industry has developed rapidly, providing mature technology and abundant seedlings for large-scale sea cucumber enhancement and aquaculture. Based on the different geographical advantages of local coastal mudflats and island bays, fishermen in various regions have summarized and explored a variety of new artificial sea cucumber aquaculture techniques in different forms and with different methods.
Offshore Raft Culture Method
Raft culture means using cages similar to fish-farming cages to carry out artificial sea cucumber aquaculture at sea. For raft culture, the sea area should preferably be an excellent harbor surrounded by mountains on three sides, sheltered from wind and with slow currents, and with a water depth of 5-9 m. The cages are made from boards or logs of moderate thickness into squares with sides of 4 m or 6 m, and the height can be set at 3-4 m according to the seawater depth and the size of the tidal range.
Each year in spring and autumn, when the seawater temperature reaches 8-12°C, it is the best season to release sea cucumber seedlings. At this time, the sea cucumber seedlings in the nursery workshop are about 200-400 individuals per kg. Because they are relatively large and strong-bodied, when released at this time the survival rate can reach more than 95%. For a cage 6 m square like this, about 20-25 kg of sea cucumber seedlings at about 200 individuals per kg can be released.
In sea areas with relatively abundant feed and floating mud, the food on the cages can basically meet the needs of the sea cucumbers. If the food is found to be insufficient, feeding must be carried out. The simplest method is to choose a sea area with unobstructed water flow and drag in some mud and sand rich in microorganisms as a supplement; artificial compound feed made from algae can also be used for feeding. Normally, the cages should be checked frequently for damage, and natural enemies such as fish fry, crabs and starfish, as well as debris such as oysters and sponges, should be removed from the cages in a timely manner.
The greatest advantages of raft culture of sea cucumbers are convenient management and a high harvest rate. Generally, after about 2 years, finished sea cucumbers can be harvested.
Beach Enclosure Culture Method
Wherever there are shrimp ponds or salt ponds, they can be slightly modified for aquaculture. Ponds can also be built by digging soil on seaside mudflats. Usually, mudflats that are not easily damaged by wind, waves and tides are chosen for pond construction. The size and shape of the pond depend on the geographical environment. Generally, the length is required to be no less than 50 m, the width no less than 30 m, and the water depth at the lowest tide between 0.8-1.3 m. The "enclosure pond" is provided with one or more inlet and outlet gates, and filter screens must be installed at the gates to prevent fish and various harmful organisms from entering.
The pond bottom simulates the natural shape of the seabed, with stones and hollow bricks piled into long ridge-like strips, leaving spaces as places for sea cucumbers to inhabit and settle. The pond bottom should preserve the original ecological environment of sea cucumbers as much as possible, and various seaweeds such as kelp, wakame, seagrass and attached diatoms should be transplanted. Before releasing seedlings, the aquaculture site must be disinfected and sun-dried. Disinfection is generally carried out by splashing limewater or similar substances.
The release density of seedlings in the pond is generally 10-15 individuals per sq m. Water exchange in beach enclosure culture mainly relies on the difference between high and low tides for water body exchange, and artificial water exchange can also be used. Generally, the daily water exchange volume is required to be about 1/3-1/4. The feed for enclosed sea cucumbers is mainly natural feed, with artificial compound feed added appropriately according to seasonal water temperature, individual sea cucumber size and stocking density.
Enclosed sea cucumbers have the characteristics of low investment, easy management, proximity to the natural environment, a high recovery rate and fast growth. The growth cycle of enclosed sea cucumbers is generally about two years.
Seabed Broadcast Stocking Method
This method mainly makes up for the insufficiency of natural reproduction of sea cucumbers by artificially releasing sea cucumber seedlings to increase the density of sea cucumbers in the sea area, thereby increasing sea cucumber production. In spring and autumn when the water temperature is suitable, when the natural water temperature reaches 8-10°C, choose a sunny, calm day, put sea cucumber seedlings of 2-3 cm or more into mesh bags or bamboo baskets, and have divers dive to the seabed to place them among the reefs, letting them crawl and disperse naturally and freely choose places to settle. The density for seabed broadcast stocking is generally 6-7 individuals per sq m. During seabed broadcast stocking, attention should be paid to the temperature difference between the pond water temperature and the sea area water temperature, which generally must not exceed 2°C. The sea area should be chosen with gentle currents, abundant feed and few natural enemies, and with seabed alternating between gravel and mud and sand.
The main features of this method are simplicity, ease of operation and low cost. Sea cucumbers grow in the natural environment and grow relatively fast, and can generally be harvested in 2 years.
Under normal circumstances, combining raft culture with beach enclosure culture, or raft culture with seabed broadcast stocking, is a relatively scientific aquaculture method.
Artificial sea cucumber aquaculture is an emerging marine aquaculture project in recent years. Due to the increasingly mature aquaculture technology and the rapid development of aquaculture area, it has now expanded into an important pillar industry. We believe that with the continuous progress of science and technology, it will have an important impact on artificial sea cucumber aquaculture and the deep processing and comprehensive utilization of sea cucumbers, ushering in a better tomorrow for our lives.