Special Topic on Sandworm Farming Techniques: A Complete Analysis of Scientific Methods and Practical Tips

Overview of Sandworms

The sandworm (Nereid), English name - Clamworm, belongs to the phylum Annelida, class Polychaeta, and is commonly known as sea worm, sea maggot, sea centipede, and sea leech. Those harvested and farmed are mostly large species of the genera Perinereis Kinberg and Neanthes Kinberg. They are worm-shaped, with larger individuals reaching more than 10 cm in body length, and some species reaching more than 20 cm. The cross-section is round or slightly flattened, with many body segments. The body is divided into head, trunk, and tail. The head consists of the prostomium and peristomium, and bears tentacles, eyes, and a mouth; inside the mouth is a proboscis, which generally bears many small dark brown teeth.

Behind the head is the trunk, and on both sides of each trunk segment are parapodia bearing setae. The setae contain venom glands, and when they pierce the skin they cause redness, swelling, and pain. The tail, also called the anal segment, has an anus and anal cirri. Sandworms are rich in nutrients and are not only a food organism eagerly eaten by fish and shrimp, but can also serve as excellent fishing bait. Coastal residents of Fujian, Guangdong, and Guangxi also regard sandworms with mature gonads as a nutritional delicacy. After drying, when boiled into soup it turns as white as milk and has an extremely delicious flavor, with a rich consistency, and is known as "natural MSG." After deep-frying it is crisp, fluffy, and fragrant, making an excellent dish to go with alcohol. Sandworms sell extremely well both domestically and for export.

Farmed species:

Because their reproductive modes are highly varied, there are some species we still cannot farm. Simply put, what can be farmed now are just a few species of the genera Neanthes and Perinereis. There is another kind, which the Japanese call "golden sandworm," commonly known as "red sandworm"; in fact there is also a red sandworm whose scientific name is rock worm, and both sell for as much as 10,000 yen per kilogram, making them rare and valuable species that are also being trial-farmed. To farm a given kind of sandworm, you must first decide based on the substrate; for example, if the bottom is clay, you cannot farm rock worms. Next is the purpose: if it is to raise shrimp well, you can only farm Neanthes.

Ecological Habits and Harvesting

Ecological habits:

Sandworms inhabit muddy and sandy substrates in the intertidal zone, digging U-shaped burrows and hiding inside them, moving with the rise and fall of the tide, hiding by day and emerging at night, and emerging onto the sand surface when feeding. Larvae mainly feed on unicellular algae, while after becoming benthic and burrow-dwelling they feed on fragments of animals and plants and detritus, and can effectively utilize protein in sludge. Their tolerance for temperature and salinity is relatively strong.

Most are dioecious, but they have no obvious reproductive system, and gonads form at sexual maturity. Most marine sandworms undergo changes in morphology and body color before reproduction, allowing distinction of females - blue-green, and males - overall milky white with red feet, known as the heteronereis form, that is, parent sandworms. At full moon they swarm and swim at the sea surface, and some males and females chase each other, with a nuptial dance phenomenon. Fertilization is external. Mature eggs are spherical, blue-green, demersal eggs, with egg diameter varying from 75-150 micrometers. The fertilized egg passes through early embryonic development, trochophore larva, nectochaete larva, and setiger juvenile stages and other developmental and metamorphic stages, and grows into an adult.

Two methods of harvesting sandworms:

Use a fine-mesh net to catch sexually mature individuals that emerge from their burrows and gather in the water to mate. Work at night during spring tides in the breeding season, and the sandworms caught are mostly for food. Dig in the intertidal zone. The burrowing depth of sandworms in mud and sand is about 25-40 cm. At low tide, carry a spade, shovel, or hoe, find the burrow opening, and dig quickly before the sandworm is alarmed and retreats deeper, taking care not to cut the worm's body, as damaged bodies are not easy to keep alive. The harvested sandworms must be protected from sun exposure and rain, so as not to affect the survival rate.

Economic value of sandworm farming:

Farming sandworms can improve pond substrate, remediate environmental pollution, and promote a virtuous cycle in marine aquaculture. Sandworms are a major protein food source for fish, shrimp, and crabs, and the rise and fall of natural sandworm resources is directly related to the abundance or scarcity of marine fisheries. They are also called "universal fishing bait," and are a high-quality sea delicacy that has already entered high-end banquets. Sandworm farming has low requirements; you only need to simply build embankments around seawater flats and you can stock them, the feed is coarse and miscellaneous with broad sources, and a large amount of nutrients can be obtained from seawater.

The long-term habitual practice of only catching without farming has severely damaged natural resources, and it has reached the point where farming is unavoidable, so current farming profits are considerable. Stocking about 200 yuan per mu can yield a profit of 2,000-3,000 yuan. Moreover, it is a one-time investment that can then roll forward, developing year by year for long-term enjoyment, and it should be said to be a shortcut to prosperity along the coast.

Farming methods:

Industrial artificial farming

First seen in Japan in the 1980s, it mostly involves first carrying out artificial seedling rearing, then implementing seedling stocking. The specific practice is mostly carried out in artificially built indoor ponds (tanks). When rearing seedlings, no sand is laid, but for stocking and grow-out, about 30 cm of coarse sand must be laid. Water is supplied daily, feed is given 2-3 times, and aeration is provided. In this way, as long as water supply is timely, temperature is suitable, density is reasonable, and feed is appropriate, it takes only half a year to grow to market size, with output generally 10 kg per pyo (about 3 kg per square meter).

Extensive pond and marsh farming

Artificial (or semi-artificial) seedling breeding is adopted, with large-area stocking in earthen ponds, focusing on shallow ponds and low-lying land currently unsuitable for shrimp farming. In view of the relatively large area of these waters and the fact that most are newly developed with poor pest elimination, while sandworms themselves are a food organism (including adults and larvae), the work of clearing ponds and filling with water must be even more rigorous than for stocking fish and shrimp, to prevent damage from various organisms and avoid affecting survival and output. Based on current results, as long as density is suitable and management is proper, output per mu can exceed 50 kg.

Enhancement-type tidal flat stocking

This is carried out from the perspective of enhancing resources. It is reported that Shandong and Liaoning have artificially stocked sandworm larvae about to burrow in a certain range of natural sea areas (intertidal zones), enhancing sandworms and achieving the encouraging result of increasing output by 50-75 times. The method is also very simple, and the social and ecological benefits are both very significant.