Sea Cucumber Aquaculture
Global fish production reached about 179 million tonnes in 2018 according last data provided by FAO (https://www.fao.org/3/ca9229en/ca9229en.pdf), with a total first sale value estimated at USD 401 billion, of which 82 million tonnes, valued at USD 250 billion, came from aquaculture production. Aquaculture accounted for 46 % of the total production and 52% of fish for human consumption.
Sea cucumber is an important economical resource considering its high and increasing demand from Asian countries, where they are consumed as food but also, as source of essential micronutrients and bioactive molecules. In 2016, it was reached the maximum of sea cucumber aquaculture production (204.7 thousand tonnes), decreasing in 2018 (176.8 thousand tonnes) (https://www.fao.org/3/ca9229en/ca9229en.pdf).
The Apostichopus japonicus’ culture (sea cucumber commercial species) is one of the most profitable aquaculture systems in China. However, aquaculture of other target sea cucumber species has already been developed, including some species distributed in the NE Atlantic and Mediterranean such as Holothuria arguinensis, Holothuria mammata, Holothuria forskali and Holothuria sanctori or from Mediterranean Sea (Holothuria tubulosa and Holothuria polii).
TARGET SPECIES IN AQUACULTURE
Holothuria arguinensis NE Atlantic
Holothuria mammata SW Mediterranean
Holothuria sanctori SW Mediterranean
Holothuria tubulosa SW Mediterranean
Holothuria polii SW Mediterranean
Holothuria forskali NE Atlantic
BREEDERS
WANGUMAQUA SLU has strict criteria for selection of its broodstock, harbouring the individuals, the main characters which will be inherited by the progeny. These external features define the most valuable and wanted “morphotypes” in the Asian market.
Breeders are caught by hand during low tides or using under water devices and/or free diving techniques following regional/national legislation (license of breeder’ catches regulated by Fisheries and Aquaculture Department). During the catches, animals are kept in buckets/containers with renewed sea water, air supply and refrigeration to avoid stress or skin damages, according protocols developed by Dr. Wangüemert through years working with sea cucumbers in CCMAR (Universidade do Algarve, Portugal). These conditions for catching, sheltering and transport comply with animal welfare principles.
Sampling Holothuria tubulosa breeders in the SW Mediterranean Sea.
Catching in free-diving Holothuria arguinensis breeders from the NE Atlantic.
Holothuria arguinensis breeder from Canary islands (NE Atlantic).
Holding Holothuria arguinensis breeders until used for gametes production.
Holothuria arguinensis breeders from Ria Formosa (South Portugal).
Dr. Wangüemert catching sea cucumber breeders in free diving (Mediterranean Sea).
INDUCTION FOR REPRODUCTION
Based on previous experience developed by Dr. Wangüemert during her years working and collaborating with Research Centers (such as CCMAR, Universidade do Algarve; IOCAS, Chinese Academy of Sciences, Institute of Oceanology) and leading several international projects, WANGUMAQUA SLU has developed several protocols to induce the reproduction of breeders (males and females) according the target species, number of breeders, sea water temperature, season, geographical location and expected production of fertilized eggs.
Thermal shock seems to be the better methodology to induce the reproduction of the Mediterranean and NE Atlantic species, being the males the first ones to release sperm and later females releasing eggs. In both cases, the gamete’ release is through a gonopore placed at the top of the dorsal anterior part of the body. Individuals from both sexes are showing during the reproduction, the typical behaviour with body swayed from side to side.
WANGUMAQUA SLU has also developed for some target species, protocols for artificial insemination, also starting with some experiments on cryopreservation of sea cucumber gametes and larvae.
Reproduction of Holothuria arguinensis male
Reproduction of Holothuria forskali male
Reproduction of Holothuria mammata male
Reproduction of H. arguinensis male and sperm collection for later artificial insemination.
Reproduction of H. arguinensis female
LARVAL DEVELOPMENT
The main target species of sea cucumbers from Mediterranean and NE Atlantic regions are showing five larvae stages including early, medium and late auricularia, doliolaria and penctactula. The three first phases named auricularia are “pelagic” larvae which are distributed in the water column of the larvae tanks; doliolaria and penctactula are “benthic” larvae showing special requirements.
The step from pelagic to benthic larvae through the settlement process is the most important time to assure a good survival rate of juveniles. The hyaline spheres from doliolaria larvae are fundamental for a right “methamorphosis” into a penctactula larvae; quality and quantity of feeding diet during those stages, larvae density in tanks, and quality of biofilm on settlement structures are essential for a profitable production of further juveniles.
For this reason WANGUMAQUA SLU has special care about the microalgae and diatoms diets for larvae. Several microalgae diets for sea cucumber larvae have already been published in scientific and public papers, most of them including different species of microalgae such as Isochrysis sp., Nannochloropsis sp., Tetraselmis sp., Chaetoceros sp, etc. In fact, there are many companies in Europe (for example Acuinuga, www.acuinuga.com) marketing microalgae diets for feeding. These prepared diets are very useful for different aquaculture species and they show optimal economical prices, decreasing cost of production in the aquaculture companies.
Feeding of a sea cucumber auricularia larva.
Check the digestion of microalgae and final defecation.
SETTLEMENT
As it was commented previously, the step going to the larvae settlement is the most important phase to ensure the success of juveniles production. Special settlement structures for sea cucumber penctactula and juveniles are available in the Chinese market; they could be purchased from different companies.
Also, the development of an optimal biofilm on the surface of these structures is fundamental for sea cucumber juveniles feeding, allowing to reach a good survival and growth rates.
Settlement structures and juveniles of sea cucumber
JUVENILE AND PRE-ADULT FATTENING
Sea cucumber juvenile fattening systems to reach pre-adult stage have been designed and developed with fish cages or land based (tanks, marsh areas or sea ranching aquaculture). Diets based on dried macroalgae and ALGAMAC 3050 (www.aquafauna.com/algamac-3050) for juvenile and pre-adult fattening are used in WANGUMAQUA SLU. Treatments of diseases (mainly for skin ulceration disease on sea cucumber) based on natural bioactives, obtained from green macroalgae and terrestrial plants, have also been developed.
Juvenile fattening
Pre-adult fattening
