Off the coast of the Hawaiian Island of Kauai, an underwater metropolis bustles. Sea turtles glide lazily by way of the surf whereas colleges of fluorescent yellow butterflyfish weave between basketball-size sea urchins and sharp corals.
However Dave Anderson isn’t distracted by the otherworldly allure of the coral reef — he’s right here on a mission. Round 70 ft under the floor, he finds his prize: a purple sea cucumber.
Anderson plucks the spiky creature from the ocean flooring and, after a quick boat journey, delivers it to a glistening 18-acre pond on the Kauai Sea Farm, on the island’s southwest coast. Anderson is the manufacturing supervisor of this small industrial operation, which raises mullet, barracuda, tilapia, and different seafood on the market to native eating places. However the sea cucumber in Anderson’s arms isn’t for consuming — not less than, not but. As an alternative, this bottom-dwelling echinoderm is the most recent member of the fish farm’s cleansing crew.
Within the wild, sea cucumbers roam the ocean flooring, hoovering up sand and digesting the fish waste, algae, and different natural matter it comprises. Sand they excrete is cleaner than sand they eat, which is why sea cucumbers are sometimes known as “the true vacuums of the ocean flooring,” says Arnold Rakaj, a marine biologist on the College of Rome.
Now, Anderson is letting these slimy organisms carry out the identical service at Kauai Sea Farm.
On seafood farms, fish waste can construct as much as dangerous ranges, fueling illness outbreaks that kill tens of millions of fish annually.
Aquaculture, or fish farming, now provides greater than half of the seafood consumed by people globally, and the trade is projected to proceed rising to assist feed rising populations. Nevertheless, land-based and offshore fish farms face a giant drawback. With a whole lot and generally 1000’s of fish swimming in the identical web, pond, or tank, uneaten meals, fish waste, and the micro organism it comprises can construct as much as dangerous ranges, fueling outbreaks of bacterial illnesses — resembling fin rot, mycobacteriosis, and bacterial gill illness — that kill tens of millions of farmed fish annually.
The uneaten feed and waste comprise vitamins like phosphorous and nitrogen that may accumulate and sink to the underside, the place they’ll gas algal blooms or feed micro organism that suck oxygen from the water, creating “hypoxic” circumstances that suffocate captive fish and kill native organisms that encompass offshore farms. Recirculating methods that filter water and take away waste may be put in, however these buildings require a variety of power and upkeep, and so they can price upward of $200,000 on a big industrial aquaculture farm.
Sea bass at a fish farm within the Adriatic Sea off the coast of Slovenia.
WaterFrame / Alamy Inventory Picture
As a substitute, fish farms can tradition sea cucumbers together with their finfish and shellfish to enhance water high quality and improve total productiveness, a large physique of analysis suggests. Now, a modest however rising variety of seafood farmers throughout Europe, North America, and elsewhere are elevating sea cucumbers to behave as dwelling Roombas in tanks, cages, and ponds. As soon as aquaculturists construct up sufficient inventory, they’ll promote a portion of their sea cucumbers for human consumption, offering one other income for his or her farms. Such efforts, say consultants, may assist scale back demand for wild sea cucumbers, that are being fished to the purpose of extinction in some locations, together with in India and in Mexico.
These initiatives are a part of a broader motion — known as “Built-in Multi-Trophic Aquaculture” (IMTA) — to revamp fish farms in order that they work extra like biologically numerous pure ecosystems than like extremely polluting monocultures. As an alternative of elevating only one marine species, like salmon or tilapia, farmers training IMTA scale back waste by cultivating a number of species from totally different ranges of the meals chain — from sea cucumbers to mussels to kelp.
“You’re attempting to imitate a pure surroundings,” says Chris Pearce, a marine researcher from Canada’s Division of Fisheries and Oceans. “So marine species are simply doing what they do naturally out within the wild. However if you mix them with different 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.
Although fish farmers in China have been elevating fish alongside different species, like kelp and clams, for hundreds of years, the observe was formally launched in Western nations simply 20 years in the past, when marine scientist and aquaculture guide Thierry Chopin first coined the time period Built-in 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 idea has gained consideration up to now few years as fish farmers search methods to attenuate their environmental affect whereas diversifying their gross sales.
Sea cucumbers could not look notably appetizing to everybody, however they’re thought of a delicacy in China and Japan. They are often ready uncooked, like sashimi, fried or, most frequently, dried then rehydrated in soups and stews. Greater than 1,250 species of sea cucumbers dwell in oceans from the tropics to the poles, and most promote for round $3 per pound, although some notably uncommon species can go for as a lot as $1,400 per pound, dried.
“Financial sustainability is [often] missed after we speak about sustainable aquaculture,” Kauai Sea Farm’s Anderson says. “In case you construct this complete farm, and it’s not economically sustainable after which it simply crashes … that’s an enormous environmental affect and nothing got here out of it.”
Diagram of a take a look at challenge in Italy wherein sea cucumbers cleaned up excrement from farmed mussels.
Grosso et al.
However there are nonetheless hurdles to scaling up. For one, getting a allow to boost multiple species on a farm is an especially arduous course of in North America and Europe, fish farmers say. And even when they can get a allow, says Halley Froehlich, an aquaculture researcher on the College of California, Santa Barbara, “it’s actually exhausting to develop a number of species in a pure manner, all of sudden.” Fish could not develop as quick as anticipated, or they might die for unknown causes.
Kauai Sea Farm began rearing native Hawaiian sea cucumbers final 12 months, with the assistance of an almost $300,000 grant from the Nationwide Oceanic and Atmospheric Administration. For the challenge, which operates with a analysis allow, 12 sea cucumbers have been pulled from the wild and launched to the pond to see if they may survive on this setting. However the pond will want many extra cucumbers to enhance its water high quality, so Anderson is working with scientists on the College of Hawaii to develop a program that induces spawning in three totally different native sea cucumber species as a strategy to scale up provide within the farm’s new land-based hatchery.
Kauai Sea Farm’s challenge remains to be too new to be declared an unqualified success, however it’s following the lead of aquaculture operations all over the world which are already testing sea cucumbers of their methods. For instance, in 2018, researchers from the College of Stirling, in Scotland, studied how sea cucumbers grew beneath a cage of sea bream at Malta Fish Farming, an offshore operation within the Mediterranean Sea. They rapidly realized that the place they put the ocean cucumbers was crucial; these positioned straight beneath the fish have been actually smothered to demise by feces, says Karl Cutajar, the examine’s lead creator. However when the researchers put them past the shadow of the ocean bream cage, the ocean cucumbers grew a lot quicker than they do within the wild, a sign that they have been thriving on the waste.
“To have the ability to change species and have versatile farming practices is nearly inconceivable” due to paperwork, says a researcher.
Numerous comparable experiments carried out with sea cucumbers and different species — resembling mussels in Italy, seabass in Scotland, and shrimp in Kenya — have additionally proven improved productiveness and water high quality on fish farms. Just lately, researchers from Canada’s Division of Fisheries and Oceans used sea cucumbers to take away the algae and muck that crush nets at Inventive Salmon, an natural fish farm in British Columbia. Although their outcomes haven’t but been printed, marine biologist Emaline Montgomery says they did see “proof of idea”: the ocean cucumbers have been hoovering up algae and salmon refuse.
“Initially, I used to be somewhat uncertain of the way it was going to go,” says Barb Collins, the biology supervisor at Inventive Salmon. “However I used to be confirmed fallacious on all fronts, and the ocean cucumbers did rather well.”
Collins remains to be skeptical that IMTA can attain industrial scale on her farm any time quickly. To achieve the long-term, the farm would wish its personal 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 rationale for the regulatory logjam is that neither Canada, america, nor Europe has simply a single entity regulating the aquaculture trade. Within the U.S., for instance, a complete of seven totally different federal companies are chargeable for regulating aquaculture, and insurance policies give attention to elevating just one marine species at a time. “So to have the ability to change species and have versatile farming practices is nearly inconceivable,” says Froehlich, of the College of California. The bureaucratic hurdles for IMTA are “extraordinary, [considering] how quickly this trade is altering and the way vital it’s turning into at a world degree for seafood manufacturing.”
Again in Hawaii, Kauai Sea Farm operates a bit in a different way than most North American industrial fish farms. It’s positioned on the Nomilo Fishpond, which is a part of a community of centuries-old Indigenous Hawaiian loko i’a — ponds linked to the ocean by slender rocky channels. Within the conventional fishing method, child fish swim into the pond from the ocean by way of a collection of gates and stay inside till they’re too huge to swim again out. Not like many conventional loko i’a, the farm has its personal land-based hatchery the place nutrient-rich water is pumped in from the pond and passes by way of a system of tanks containing oysters, clams, sea urchins, and sea cucumbers earlier than circulating again to the supply. Each species has its personal function to play in sustaining the farm, following each the modern-day idea of IMTA and the loko i’a practice. As Lynn Taylor, the native Hawaiian proprietor of Kauai Sea Farm, places it, “We’re principally the MacGyver of fishponds.”
Nonetheless, Kauai Sea Farm just isn’t proof against the issues that different fish farms face when attempting to boost multiple species. It hasn’t but cracked the code of easy methods to reliably management the reproductive cycles of the ocean cucumbers. “Let’s say this turns into a industrial factor,” Anderson says. “You possibly can’t simply lose a 12 months of manufacturing as a result of the animals didn’t cooperate that 12 months.” He provides, “They’re very sophisticated for such a slug-looking creature.”
Lately, scientists in Sweden, Vietnam, and Sri Lanka have discovered easy methods to efficiently spawn different sea cucumber species from their areas, so Anderson hasn’t but misplaced hope. Actually, he’s attempting out one other spawning methodology this month. If the workforce can hold the ocean cucumbers alive to maturity, Kauai Sea Farm may ultimately have each a bigger cleansing crew for the pond — and a brand new seafood product to promote.
