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Sea Urchin

Description

seaurchin1SEA URCHIN

Sea urchin is one of the major shellfish resources all over the world. In the Philippines, its commercial culture is still in its developing stage. It was in fact started primarily as a resource enhancement tool to address the severe depletion of the resource due to excessive gathering of wild stocks. An obscure cousin of the starfish, sea urchins live in shallow marine waters with its gonads or roe as its only edible part. In Japan it is regarded as a delicacy called the "uni", and is also considered as an exotic food all around Southeast Asia and the United States.

Locally known as "maritangtang" in the Ilocos Region, "kuden kuden" in Bolinao and "tuyom" in the Visayas, the initial grow-out culture of sea urchins was undertaken through sea pens at Brgy Nalvo, Sta. Maria, Ilocos Sur in 1998. In the same year, the promotion of community-based grow-out culture was started in Bolinao, Pangasinan and several verification trials were also conducted in suitable areas of Ilocos Norte and La Union Thereafter, technology innovations to improve culture methods were demonstrated and promoted for adoption. DA-BFAR-RFO-1 has been vigorously promoting the cage culture of sea urchins for years now. Assessment of potential sites was undertaken, and demonstration cages were put up in coordination with The Local Government Units (LGUs) and willing cooperators or technology adopters.
(Source: Bureau of Agricultural Research, Date accessed 27 March 2014)

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Cultural Management

Production Process/Operation

Assessment and selection of the project site
Protected coves are potential sites for sea urchin farming, however, the project site will be selected with the following technical considerations:

  • existence of sea urchin stocks in the area;
  • presence of seagrass beds;
  • high water movement and tidal flushing;
  • sheltered from storms and bad weather,
  • no nearby freshwater sources such as river mouths;
  • sufficient depths (at least 1-1 5m deep at low tide) to prevent sea urchins from drying out and being exposed to freshwater in case of heavy rains;
  • free from pollution;
  • visible and accessible from the shore;
  • Should not be within a navigational route.

1. Avoid building cages in area with very low salinity because this is stressful for sea urchins and may result in mass mortality.

2. Cages should be ideally situated in a sheltered area where wild T. gratilla are naturally found.

3. Avoid areas prone to 'kulaba' or water poison.

4. Stock the cages with fresh Sargassum (brown algae) regularly even if some food still remains. This is to ensure that urchins feed at maximum rates and consequently grow fast and develop large gonads.

5. For beginners, the UP-MSI recommends to start with about 3-4 grow-out cages, each with approximately 1000 - 5000 seedstock species (about 25-500 individuals per square meter).

Cage Construction and installation

Cages used have the following dimensions, 2.4m x 1 2m x 0.6m and made of polyethylene plastic screens and plain round bars as frames The cages are installed in assessed and feasible sites, the cage bottom at 1 foot above sea floor and the cage top should be at 0.5m below water level during low tides. The cages are also set at least 2 feet apart to ensure good water flow and prevent clogging of wastes and debris.

Modular System Culture

The modular system of culture (7 cages/module) is now being recommended for sustainable production, as illustrated below.

  • stocking of juveniles every 2 months
  • transfer of stocks every 2 months
  • harvest every 2 months

In the modular system, cage 1 will be stocked every 2 months with 2,000 pcs sea urchin juveniles (1-2 cm TD) After 2 months of culture, stocks will be transferred to cages 2 and 3at 1, 000 pcs/cage Stocks from cages 2 and 3 (3-4 cm TD) will then be transferred to cages 4,5,6 and 7 at 500 pcs/cage to be cultured and harvested after 2 months reaching 7-8 cm TD. After 2 months, cage 1 can be stocked with small sizes to start the second cycle.

Note: For newly established project, cages will be initially stocked with different sizes of sea urchin juveniles to fully utilize all cages


Operation and Management

Sea urchins are cultured for a period of approximately 6-7 months or until the stocks reaches 7-8 cm test diameter (TD). The stocks are fed with sargassum or aragan once or twice a week. Each cage is liberally stocked with fresh sargassum to ensure that they feed at maximum rates for growth and development of large gonads. The cages are also regularly cleaned of leftover algae or debris each time they are fed Periodical checking of growth and survival of stocks should be undertaken.
Stripping an area of Sargassum for feeding the caged urchins may result in the eventual denudation of the algal bed. To avoid this, do not harvest Sargassum plants by pulling them up from the seafloor together with their holdfast or "roots". Use a small knife or sickle to selectively harvest only the plant's secondary branches. Leave the roots and the primary axis intact, so that the plant is able to regenerate itself for future harvesting.


Harvesting and Marketing

Harvesting is done when the stocks reached a test diameter of 7-8 cm The modular system of culture will ensure three harvests per year (Harvest every two months). Sea urchins are sold fresh or processed (roe form) in the local markets or to direct buyers like restaurants/hotel operators.
When harvesting, keep in mind that bigger urchins command a better price.
Harvesting is done after 6-8 months or when the stocks reach 7-8 cm TD.

 Source: Bureau of Agricultural Research, Date accessed 27 March 2014