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Climate ChangeAre Sea Cucumbers a Cleanup Solution to Fish Farm Pollution?

Are Sea Cucumbers a Cleanup Solution to Fish Farm Pollution?

Off the coast of the Hawaiian Island of Kauai, an underwater metropolis bustles. Sea turtles glide lazily through the surf while schools of fluorescent yellow butterflyfish weave between basketball-size sea urchins and sharp corals.

But Dave Anderson isn’t distracted by the otherworldly charm of the coral reef — he’s here on a mission. Around 70 feet below the surface, he finds his prize: a red sea cucumber.

Anderson plucks the spiky creature from the ocean floor and, after a temporary boat ride, delivers it to a glistening 18-acre pond on the Kauai Sea Farm, on the island’s southwest coast. Anderson is the production manager of this small business operation, which raises mullet, barracuda, tilapia, and other seafood on the market to local restaurants. However the sea cucumber in Anderson’s hands isn’t for eating — a minimum of, not yet. As a substitute, this bottom-dwelling echinoderm is the latest member of the fish farm’s cleansing crew.

Within the wild, sea cucumbers roam the ocean floor, hoovering up sand and digesting the fish waste, algae, and other organic matter it accommodates. Sand they excrete is cleaner than sand they devour, which is why sea cucumbers are sometimes called “the true vacuums of the ocean floor,” says Arnold Rakaj, a marine biologist on the University of Rome.

Now, Anderson is letting these slimy organisms perform the identical service at Kauai Sea Farm.

On seafood farms, fish waste can construct as much as harmful levels, fueling disease outbreaks that kill hundreds of thousands of fish every year.

Aquaculture, or fish farming, now supplies greater than half of the seafood consumed by humans globally, and the industry is projected to proceed increasing to assist feed growing populations. Nonetheless, land-based and offshore fish farms face an enormous problem. With a whole lot and sometimes hundreds of fish swimming in the identical net, pond, or tank, uneaten food, fish waste, and the bacteria it accommodates can construct as much as harmful levels, fueling outbreaks of bacterial diseases — akin to fin rot, mycobacteriosis, and bacterial gill disease — that kill hundreds of thousands of farmed fish every year.

The uneaten feed and waste contain nutrients like phosphorous and nitrogen that may accumulate and sink to the underside, where they will fuel algal blooms or feed bacteria that suck oxygen from the water, creating “hypoxic” conditions that suffocate captive fish and kill native organisms that surround offshore farms. Recirculating systems that filter water and take away waste could be installed, but these structures require quite a lot of energy and maintenance, they usually can cost upward of $200,000 on a big business aquaculture farm.

Sea bass at a fish farm within the Adriatic Sea off the coast of Slovenia.
WaterFrame / Alamy Stock Photo

Instead, fish farms can culture sea cucumbers together with their finfish and shellfish to enhance water quality and increase overall productivity, a large body of research suggests. Now, a modest but growing variety of seafood farmers across Europe, North America, and elsewhere are raising sea cucumbers to act as living Roombas in tanks, cages, and ponds. Once aquaculturists construct up enough stock, they will sell a portion of their sea cucumbers for human consumption, providing one other income for his or her farms. Such efforts, say experts, could help reduce demand for wild sea cucumbers, that are being fished to the purpose of extinction in some places, including in India and in Mexico.

These initiatives are a part of a broader movement — called “Integrated Multi-Trophic Aquaculture” (IMTA) — to revamp fish farms in order that they work more like biologically diverse natural ecosystems than like highly polluting monocultures. As a substitute of raising only one marine species, like salmon or tilapia, farmers practicing IMTA reduce waste by cultivating multiple species from different levels of the food chain — from sea cucumbers to mussels to kelp.

“You’re attempting to mimic a natural environment,” says Chris Pearce, a marine researcher from Canada’s Department of Fisheries and Oceans. “So marine species are only doing what they do naturally out within the wild. But while you mix them with other species, what they’re doing is making a service for the ecosystem.”

“What’s waste for any individual is gold for any individual else,” one scientist says of sea cucumbers feasting on fish feces.

Though fish farmers in China have been raising fish alongside other species, like kelp and clams, for hundreds of years, the practice was formally introduced in Western nations just 20 years ago, when marine scientist and aquaculture consultant Thierry Chopin first coined the term Integrated Multi-Trophic Aquaculture. “What’s waste for any individual is gold for any individual else,” says Chopin, referring to the ocean cucumbers feasting on fish feces. The concept has gained attention previously few years as fish farmers seek ways to reduce their environmental impact while diversifying their sales.

Sea cucumbers may not look particularly appetizing to everyone, but they’re considered a delicacy in China and Japan. They could be prepared raw, like sashimi, fried or, most frequently, dried then rehydrated in soups and stews. Greater than 1,250 species of sea cucumbers live in oceans from the tropics to the poles, and most sell for around $3 per pound, though some particularly rare species can go for as much as $1,400 per pound, dried.

“Economic sustainability is [often] ignored once we discuss sustainable aquaculture,” Kauai Sea Farm’s Anderson says. “In case you construct this whole farm, and it’s not economically sustainable after which it just crashes … that’s an enormous environmental impact and nothing got here out of it.”

Diagram of a test project in Italy in which sea cucumbers cleaned up excrement from farmed mussels.

Diagram of a test project in Italy during which sea cucumbers cleaned up excrement from farmed mussels.
Grosso et al.

But there are still hurdles to scaling up. For one, getting a permit to lift a couple of species on a farm is an especially arduous process in North America and Europe, fish farmers say. And even when they can get a permit, says Halley Froehlich, an aquaculture researcher on the University of California, Santa Barbara, “it’s really hard to grow multiple species in a natural way, unexpectedly.” Fish may not grow as fast as expected, or they might die for unknown reasons.

Kauai Sea Farm began rearing native Hawaiian sea cucumbers last 12 months, with the assistance of a virtually $300,000 grant from the National Oceanic and Atmospheric Administration. For the project, which operates with a research permit, 12 sea cucumbers were pulled from the wild and introduced to the pond to see in the event that they could survive on this setting. However the pond will need many more cucumbers to enhance its water quality, so Anderson is working with scientists on the University of Hawaii to develop a program that induces spawning in three different native sea cucumber species as a strategy to scale up supply within the farm’s latest land-based hatchery.

Kauai Sea Farm’s project remains to be too latest to be declared an unqualified success, however it is following the lead of aquaculture operations around the globe which can be already testing sea cucumbers of their systems. For instance, in 2018, researchers from the University of Stirling, in Scotland, studied how sea cucumbers grew under a cage of sea bream at Malta Fish Farming, an offshore operation within the Mediterranean Sea. They quickly learned that where they put the ocean cucumbers was critical; those placed directly under the fish were literally smothered to death by feces, says Karl Cutajar, the study’s lead creator. But when the researchers put them beyond the shadow of the ocean bream cage, the ocean cucumbers grew much faster than they do within the wild, a sign that they were thriving on the waste.

“To give you the option to change species and have flexible farming practices is nearly unattainable” due to bureaucracy, says a researcher.

Quite a few similar experiments performed with sea cucumbers and other species — akin to mussels in Italy, seabass in Scotland, and shrimp in Kenya — have also shown improved productivity and water quality on fish farms. Recently, researchers from Canada’s Department of Fisheries and Oceans used sea cucumbers to remove the algae and muck that weigh down nets at Creative Salmon, an organic fish farm in British Columbia. Though their results haven’t yet been published, marine biologist Emaline Montgomery says they did see “proof of concept”: the ocean cucumbers were hoovering up algae and salmon refuse.

“Originally, I used to be just a little unsure of the way it was going to go,” says Barb Collins, the biology manager at Creative Salmon. “But I used to be proven mistaken on all fronts, and the ocean cucumbers did rather well.”

Collins remains to be skeptical that IMTA can reach business scale on her farm any time soon. To achieve the long-term, the farm would want its own sea cucumber hatchery so it wouldn’t deplete wild populations. And getting a license for farming sea cucumbers, she says, “can take a major period of time.”

A part of the explanation for the regulatory logjam is that neither Canada, the US, nor Europe has just a single entity regulating the aquaculture industry. Within the U.S., for instance, a complete of seven different federal agencies are liable for regulating aquaculture, and policies give attention to raising just one marine species at a time. “So to give you the option to change species and have flexible farming practices is nearly unattainable,” says Froehlich, of the University of California. The bureaucratic hurdles for IMTA are “extraordinary, [considering] how rapidly this industry is changing and the way essential it’s becoming at a worldwide level for seafood production.”

Dave Anderson of Kauai Sea Farm gathers a sea cucumber.

Dave Anderson of Kauai Sea Farm gathers a sea cucumber.
Kauai Sea Farm

Back in Hawaii, Kauai Sea Farm operates a bit in a different way than most North American business fish farms. It’s positioned on the Nomilo Fishpond, which is a component of a network of centuries-old Indigenous Hawaiian loko i’a — ponds connected to the ocean by narrow rocky channels. In the normal fishing technique, baby fish swim into the pond from the ocean through a series of gates and remain inside until they’re too big to swim back out. Unlike many traditional loko i’a, the farm has its own land-based hatchery where nutrient-rich water is pumped in from the pond and passes through a system of tanks containing oysters, clams, sea urchins, and sea cucumbers before circulating back to the source. Every species has its own role to play in maintaining the farm, following each the modern-day concept of IMTA and the loko i’a practice. As Lynn Taylor, the native Hawaiian owner of Kauai Sea Farm, puts it, “We’re principally the MacGyver of fishponds.”

Still, Kauai Sea Farm will not be resistant to the issues that other fish farms face when trying to lift a couple of species. It hasn’t yet cracked the code of the best way to reliably control the reproductive cycles of the ocean cucumbers. “Let’s say this becomes a business thing,” Anderson says. “You’ll be able to’t just lose a 12 months of production since the animals didn’t cooperate that 12 months.” He adds, “They’re very complicated for such a slug-looking creature.”

Lately, scientists in Sweden, Vietnam, and Sri Lanka have found out the best way to successfully spawn other sea cucumber species from their regions, so Anderson hasn’t yet lost hope. The truth is, he’s trying out one other spawning method this month. If the team can keep the ocean cucumbers alive to maturity, Kauai Sea Farm could eventually have each a bigger cleansing crew for the pond — and a latest seafood product to sell.


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