Aquafeed Sea cucumber article – July 2022
Blue flashes of bioluminescence trail from my fins like pixie dust as I survey the project sea pen. How many sea cucumbers are visible tonight? This species often burrows, making it hard to estimate the population in the pen. My swim tonight contributes to research we are doing to better understand and manage this fascinating animal. I spot a blue crab intent on adding one of our juvenile sea cucumber to his menu. A moment later I’ve trapped him, he is now an item on my menu.
The humble sea cucumber is a curious animal. They are members of the phylum Echinodermata along with sea stars, sea urchins, and sand dollars, to name just a few. Globally, there are at least 1700 species of sea cucumbers. They are found in all the oceans of the world and at all depths.
Most sea cucumbers creep along the seabed on hundreds of tiny tube feet. Others live in tubes in the sea bottom and a few species swim. These simple animals have no brain, relying on a nerve network instead – like our human reflex system. They have no eyes, yet they can detect changes in light levels through their skin. At one end is their mouth, for eating. However, the rear end is used for both elimination… and breathing. They absorb oxygen from the water through their vascular system.
Sea cucumbers are a vital part of the nutrient recycling process in marine ecosystems. They eat sand, digesting the organic matter in it. What comes out is then cleaner than what went in! They play an important role in reducing the organic load in benthic environments, which makes them a species of interest in keeping mariculture sites cleaner.
Sea cucumbers cannot outrun predators; instead, they have several defences. When attacked, they will expel half of their internal organs, presumably to scare the animals hunting them. They can renew these organs in a few days. Their amazing ability to regenerate foiled many of our early efforts to tag or mark individuals.
Some have sticky Cuvierian tubules they release to entangle predators. A toxin in these tubules and secreted onto their skin, called holothurin, is also poisonous to fish. Fishermen gutting and cleaning harvested sea cucumbers often find fish kills down-current.
Sea cucumbers are numbered among the four ocean treasures of Cantonese cuisine, which also includes shark fins, abalone, and fish bladders. They have long been regarded as a delicacy in China, Japan, Korea, Vietnam, Malaysia, and Singapore.
Generally, they are sold dehydrated, though they can be purchased fresh or frozen. Typically, after rehydrating they are added into soups or stir fry, eaten raw or pickled. Being relatively bland, they are often combined with flavour-infusing ingredients. Their value in Asian cultures is reflected in the fact that they are often packaged in ornate boxes to be given as status gifts.
Sea cucumbers are not only valued for food. There is a significant and popular industry for sea cucumber health products in Asia and within Asian diaspora populations around the world. The Chinese word for sea cucumbers, Hǎishēn, literally means ‘ginseng of the sea’. Extracts of the animals are used in traditional Chinese medicine to treat ailments like arthritis, cancer, frequent urination, and impotence.
These many valued characteristics of sea cucumbers has been translated into multi-billion-dollar industry globally. Asian businessmen have scoured the world, encouraging fishermen to harvest marketable local sea cucumbers. As a result, natural stocks of commercial species have been severely depleted in many parts of the world. Governments often react by placing bans on collection, but these policies are difficult to enforce.
In the 1990’s I surveyed commercially important sea cucumber species in one tropical country to establish a reference point. Within ten years the populations of sea cucumbers in the waters surrounding that country had been decimated. At the time of our survey the cucumbers used to be plentiful in the shallow reef flats, now the only way to find market weight specimens requires scuba diving over thirty metres.
Recognising that current harvesting habits were not sustainable, and that the market would remain voracious, scientists around the world began to research temperate and tropical sea cucumber species with an eye towards culturing them. By 1970, China and Japan were successful in starting culture of temperate species.
More recently the efforts of this global research effort have resulted in a better understanding of some important tropical species. These investigations revealed insights into key stages of their lifecycle: from spawning, through settling out, development of juvenile seedstock, and then grow-out in sea pens until they reach market weight. Applied experience over time has helped to translate this research into culture strategies, revealing both the challenges and best practices for each phase. Much of this research has focused on one popular tropical species, Holothuria scabra.
Over the past ten years I have been consulting with Innovare, one of several initiatives around the world that have drawn on the above research to develop mariculture strategies for H. scabra. After years of trial and error, and through collaboration with similar projects, Innovare has gained control over all the lifecycle stages of H. scabra in their environment. They are now successfully breeding their own seedstock to place in village sea pens.
Innovare project staff intentionally wanted to pursue a wholistic approach to sea cucumber production for the Asian market. So, they have invested in a social enterprise model which supports local community development through a sustainable business structure. With this basic approach they then sought out an Indonesian fishing village which was already demonstrating respect for their environment along with interest in exploring opportunities in sea farming.
When a community was chosen, project leaders with a deep understanding of local language and culture talked with community leaders to develop a plan. Agreements were made on profit-sharing for sea cucumber stock sold from cages off their coast, with the proceeds going to support community development projects.
Initial capital was then invested in infrastructure such as the hatchery, a laboratory and sea pens.
Local fishermen were hired to build and maintain project pens and facilities, tend the project stock, track health and growth, act as security guards, and process the harvest. Innovare project staff work hard to build relationships and maintain goodwill in these artisanal fishing communities.
Many of the project and hatchery staff are hired locally, then trained to run the hatchery and engage villagers as mariculture extension workers. They also have a partnership with a nearby university, who send students to carry out research projects at the Innovare hatchery, furthering both the project and university goals. An internship program is planned to start sometime in the next year.
Marine protected areas (MPAs) have the ability to reseed and restore overexploited fisheries, such as we find in waters around the villages near the Innovare project. Prior to the project’s arrival, this particular island had established an MPA nearby. They have welcomed the project’s help to develop this further – a plan delayed by the worldwide pandemic. We hope to take this up again this next year.
Abang Sap emerged from the murky shallows cradling several H. scabra to weigh. His home, built over the water, overlooks the family pen. Abang’s sea cucumbers grow more quickly than those in other project pens, situated a few hundred metres away on either side. We don’t know why, more things to research.
A neighbour collecting oysters nearby stands and runs towards us, beaming as he holds out his hands. He has a juvenile H. scabra, the tenth one found on the reef this week. The natural spawning in project pens are beginning to reseed the reef flats.
Just a few years ago islanders had collected H. scabra to sell to trans-national businesses, completely decimating the population along all the reefs in this part of Indonesia. How satisfying to see a sign that the species could be restored once again.
Currently Innovare is looking for new locations, not only to farm sea cucumbers but also to set up other low-capital hatchery systems to support local mariculturalists.
In many ways our project is a young pioneering initiative still in its formative stages. It has been a bit of a dance: moving a few steps forward, a step back, then forward again. Despite the worldwide pandemic, the project has progressed in some significant ways. Currently it is on track to benefit both these artisanal fishing villages and assist in the restoration process for local fisheries.
For more about the Innovare project, visit their website: https://innovaredev.com
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Steve Holloway is a marine biologist and author. He lives with his family in England and consults with projects like Innovare as part of his work with a Christian charity. His debut novel, Pelagia: Between the Stars and the Abyss, was published by Lion Fiction in June 2021. It is a near future thriller set against the drama of pioneering and settling the open seas.