Sea cucumber Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothuria ...

stocks have been overexploited in the wild, resulting in incentives to grow them by

aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...

. Aquaculture means the sea cucumbers are farmed in contained areas where they can be cultured in a controlled manner. In China, sea cucumbers are cultured, along with prawns and some fish species, in integrated multi-trophic systems. In these systems, the sea cucumbers feed on the waste and feces from the other species. In this manner, what would otherwise be polluting byproducts from the culture of the other species become a valuable resource that is turned into a marketable product. __TOC__

History

The Chinese and Japanese were the first to develop successful hatchery technology for '' Apostichopus japonicus'', prized for its high meat content and success in commercial hatcheries.James, B. D. (2004)
Captive breeding of the sea cucumber, ''Holothuria scabra'', from India
In Lovatelli, A. (comp./ed.); Conand, C.; Purcell, S.; Uthicke, S.; Hamel, J.-F.; Mercier, A. (eds.) ''Advances in sea cucumber aquaculture and management''. FAO Fisheries Technical Paper. No. 463. Rome, FAO. 2004. 425p. A second species, '' Holothuria scabra'', was cultured for the first time using these techniques in India in 1988. In recent years Australia, Indonesia, New Caledonia, Maldives, Solomon Islands and Vietnam have also successfully cultured ''H. scabra'' using the same technology, which has since been expanded to other species.

Broodstock

Sea cucumbers to be used as

broodstock Broodstock, or broodfish, are a group of mature individuals used in aquaculture for breeding purposes. Broodstock can be a population of animals maintained in captivity as a source of replacement for, or enhancement of, seed and fry numbers.Waple ...

are either collected from the wild or are taken from commercial harvests. Only the largest and healthiest individuals are used for broodstock, as the success of a hatchery relies on the healthy condition of brood individuals.James, D. B., Gandhi, A. D., Palaniswamy, N., & Rodrigo, J. X. (1994)
Techniques and Culture of the Sea-cucumber ''Holothuria scabra''
CMFRI Special Publication(57), 1–40. These individuals are kept in tanks with at least 6 inches of sand to allow burrowing behaviour. Water is changed every day and sand is changed every fortnight. Sea cucumbers are fed with a paste made from freshly collected

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

added to the tanks once a week to settle on sand where they feed. If water conditions are not right and if proper food is not provided sea cucumbers will eviscerate or re-absorb their

gonad A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sper ...

s rendering them unfit for spawning.

Spawning

Temperature shock involves cooling and heating of seawater by 3–5°C until spawning is induced.Giraspy, D. A. B., & Walsalam, I. G. (2010)
Aquaculture potential of the tropical sea cucumbers ''Holothuria scabra'' and ''H. lessoni'' in the Indo-Pacific region
''SPC Beche-de-mer Information Bulletin''(30), 29–32. This is achieved by first reducing the temperature of the water by 3–5°C. The sea cucumbers are left for five minutes before they are exposed to ‘normal’ (depending on species and climate) temperature seawater, where the small rise in water temperature is sufficient to induce spawning.Laxminarayana, A. (2005)
Induced spawning and larval rearing of the sea cucumbers, ''Bohadschia marmorata'' and ''Holothuria atrain Mauritius''
SPC Beche-de-mer Information Bulletin (22), 48–52. Males tend to spawn first which then induces females to release their eggs. Spawning stimulation can also be achieved through lightly drying the broodstock followed by exposure to a powerful jet of seawater. Sea cucumbers are dried for 30 minutes in the shade and then are exposed to a powerful jet of seawater for 30 minutes. Usually 60–90 minutes later males will release their sperm, and 30 minutes after that females will swell and release eggs in rapid intermittent jets. Though many species of sea cucumbers can be induced to spawn using both of these methods, temperature shock is usually considered to be the preferred method. Often spawn obtained from drying and wetting with a jet of water does not produce viable gametes. Spawning induction and successful fertilization has only been achieved in some species of sea cucumbers and the likelihood that a method will work or not is highly dependent on the species.

Larvae

The first month after hatching is particularly crucial and mortality during the

larval A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The l ...

phases is particularly high. Larval survival drops to 30 – 34% after the first 20 days of hatching and larval development.Battaglene, S. C., Seymour, J. E., & Ramofafia, C. (1999)
Survival and growth of cultured juvenile sea cucumbers, ''Holothuria scabra''
Aquaculture, 178(3–4), 293–322.Ivy, G. and D. A. B. Giraspy (2006)
Development of large-scale hatchery production techniques for the commercially important sea cucumber ''Holothuria scabra var. versicolor'' (Conand, 1986) in Queensland, Australia
. SPC Beche-de-mer Information Bulletin(24). Larvae usually hatch 48 hours after fertilisation and spend their first 17 days as feeding larvae or

auricularia ''Auricularia'' is a genus of fungi in the family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maint ...

. During this phase they are fed on a mix of planktonic

microalgae Microalgae or microphytes are microscopic algae invisible to the naked eye. They are phytoplankton typically found in freshwater and marine systems, living in both the water column and sediment. They are unicellular species which exist indiv ...

(''Rhodomonas salina'', ''Chaetoceros calcitrans'', ''C. mulleri'', ''

Isochrysis galbana ''Isochrysis galbana'' is a species of Haptophyta. It is the type species of the genus '' Isochrysis''. It is an outstanding food for various bivalve larvae and is now widely cultured for use in the bivalve aquaculture industry. This unicellular ...

'' and ''Pavlova lutheri'' are most commonly used). The proportions and overall quantity of microalgal feed species varies with larval stage, and the quantity is gradually increased as larvae grow until they metamorphose into the doliolaria or non-feeding phase (around day 17.) Individuals in this phase of their development are put into a tank with settlement cues. These may include food items such as seagrass extract, seaweed extract, Algamac2000, Algamac Protein Plus, dead algae,

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

diatom A diatom (Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising sev ...

s (''

Nitzchia ''Nitzschia'' is a common pennate marine diatom. In the scientific literature, this genus, named after Christian Ludwig Nitzsch, is sometimes termed ''Nitzchia'', and it has many species described, which all have a similar morphology. Occurrenc ...

sp.'' and ''

Navicula ''Navicula'' is a genus of boat-shaped diatom algae, comprising over 1,200 species. ''Navicula'' is Latin for "small ship", and also a term in English for a boat-shaped incense-holder. Diatoms — eukaryotic, primarily aquatic, single-cell ...

sp.'') and spirulina. Around day 19 of development the larvae transform into their pentacula phase and settle. Plates or

polythene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes and containers including bott ...

sheets are provided as

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (locomotion), the surface over which an organism lo ...

for larvae to settle on and to feed off. Benthic diatoms ''Nitzchia'' sp. and ''Navicula'' sp. are most effective as settlement cues.

Nursery

Juveniles are sometimes transferred to a sand-based feeding substrate in nursery tanks when they reach 10 mm; however, survival of juveniles is better if they are allowed to grow to 20 mm before transferral to sand. Juveniles are grown for a few months until they reach 5–7 cm when they are moved out to sea ranches or into ponds.

Grow out

Sea ranching Mariculture or marine farming is a specialized branch of aquaculture (which includes freshwater aquaculture) involving the cultivation of marine organisms for food and other animal products, in enclosed sections of the open ocean ( offshore mar ...

is carried out in sheltered bays with seagrass in areas with few predators. The sea cucumbers can be kept in pens in shallow water made of fine wire mesh or bamboo, and in deeper water they are raised in cages made from fine woven mesh or in tub enclosures on the seafloor. They can also be kept and grown in ponds with appropriate water exchange and movement. Individual growth is density-dependent and is stunted at high densities. Monitoring water quality and growth characteristics are essential to survival during this phase. Sea cucumbers are ready to harvest after 12 months of grow out.

Asexual methods

Two sea cucumber species ''

Thelenota ananas ''Thelenota ananas'', also known as pineapple sea cucumber, oloturia ananas, tripang, prickly skin cucumber, pointed teat sea cucumber, armoured sea cucumber, giant sea cucumber, sand fish or prickly redfish, is a species of sea cucumber found in ...

'' (prickly redfish) and ''

Stichopus chloronotus ''Stichopus chloronotus'' is a species of sea cucumber. Common names include the greenfish sea cucumber, the spiky sea cucumber and the black knobby sea cucumber. It is native to the Indo-Pacific region. It has a wide range and is abundant and t ...

'' (greenfish) have been found capable of asexual propagation through

transverse fission Strobilisation or transverse fission is a form of asexual reproduction consisting of the spontaneous transverse segmentation of the body. It is observed in certain cnidarians and helminths. This mode of reproduction is characterized by high offspr ...

, the process whereby an organism is cut in half and completely regenerates the missing half. Rubber bands are placed around the middle of the sea cucumbers which induces them to undergo fission within 1–2 weeks. After separating, the posterior half regrows a complete

anterior Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

half, and vice versa. This happens within 3–7 months, producing two new fully-grown individuals from one. Survival from this process by these species was found to be 80% or greater.Reichenbach, N., & Holloway, S. (1995)
Potential for Asexual Propagation of Several Commercially Important Species of Tropical Sea Cucumber (Echinodermata)
Journal of the World Aquaculture Society, 26(3), 272–278. Though this technique is not suitable for all sea cucumber species, it may provide a cheaper and faster alternative method of obtaining prickly redfish and greenfish for aquaculture.

Polyculture

Sea cucumbers are currently cultured in polyculture with prawns and some fish species. Their presence in the bottoms of the pens or nets, where they feed on debris composed of feces, excess food, algae, and other particulate

organic matter Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have c ...

, significantly reduces fouling of water and equipment.Ahlgren, M. O. (1998)
Consumption and Assimilation of Salmon Net Pen Fouling Debris by the Red Sea Cucumber ''Parastichopus californicus'': Implications for Polyculture
Journal of the World Aquaculture Society 29(2): 133–139. China currently produces around 90,000 tons of sea cucumbers using these practices and enhanced growth of sea cucumber juveniles has been reported when they are grown at the bottom of prawn farms. Farming sea cucumbers with the fouling debris of other aquaculture species helps to mitigate the impacts of marine farms'

effluent Effluent is wastewater from sewers or industrial outfalls that flows directly into surface waters either untreated or after being treated at a facility. The term has slightly different meanings in certain contexts, and may contain various pollut ...

s and turns these wastes into a marketable product.

Notes

Further references

* Lovatelli A, Conand C, Purcell S, Uthicke S, J Hamel S and Mercier A (Eds) (2004)
Advances in sea cucumber aquaculture and management
''FAO Fisheries technical paper'' 463. Rome. * Toral-Granda V, Lovatelli A and Vasconcellos M (Eds) (2008

''FAO Fisheries technical paper'' 516. Rome. {{fisheries and fishing Sea Cu Holothuroidea Commercial echinoderms