Aquaculture Magazine

October/November 2015

A Mess of Mesh, or a Web of Wonder? New marvels protect against ‘net losses’ in open ocean aquaculture

By Neil Anthony Sims

One of the fundamental principles of open ocean aquaculture is to keep the sharks on one side of the netting, and the fish on the other.

By Neil Anthony Sims*

It really doesn’t work very well if you get them mixed up.

And nothing takes the luster off a sunny morning faster, for a fish farmer, than to show up at your farm site, peer over the side of the boat, and see a school of fish outside the net pen that look disturbingly similar to the fish that were inside the net pen the last time you checked. Breaches in the mesh netting can be truly catastrophic. Escapee fish bear an uncanny resemblance to $20 bills swimming away, straight out of your bottom line and into your “Losses” column.

How expensive can escapees be? Norwegian salmon producer SalMar is waiting for the permits to launch an offshore net pen that could reportedly yield up to 8,000 tonnes of salmon per cohort. Assume farm-gate value for Atlantic salmon of, say, $4.50 per kg, and that totes up to a harvest value of around USD $36 million per cage. That’s an awful lot of fish and money that is entirely dependent on the integrity of one layer of netting.

Sadly, we don’t have to rely on hypothetical extrapolations to illustrate the risk posed by containment net failures: the IntraFish AquaNor blog from August noted “one company reporting losses of $10 million from predators”. (Not surprisingly, the company wished to remain anonymous).

Escaped fish are also responsible for a large measure of the uncertainty that makes some investors squeamish about our industry. And escapees result in bad press, and bad public relations for the company, and the industry as a whole.

What’s even worse than escaped fish? An entangled marine mammal. While I cannot speak from experience, I can imagine the luster being stripped off our poor fish farmer’s morning all the faster if they were to find Flipper, or Shamu - or some other doey-eyed, bewhiskered creature - wrapped up all cold and stiff in their pen netting.

Open ocean aquaculture, with its greater exposure to ocean energy, and to charismatic megafauna – it is, after all open ocean - has been heavily scrutinized by skeptics as being at greater risk of farmed fish escapes or marine mammal entanglements. Some of the early experiences with offshore fish farm sites were indeed very (for want of a better euphemism) ‘educational’ in this regard. But the rapidity with which new technologies have been developed and then adopted is highly illustrative of the innovation-driven character of the offshore aquaculture industry and the individuals that populate it. This is worth celebrating, perhaps. So while this month’s column might end up sounding like a shameless plug for the manufacturing companies of some of the recently-developed netting materials, it is actually intended to be a collective, congratulatory pat on the back. When you all out there are good, you can be pretty darn good!

The challenges with standard nylon netting in open ocean aquaculture are readily apparent to anyone with experience with the material and the environment. Large sharks, seals and sea lions, dolphins… they are all a natural part of the offshore waters in which we work. And they all want to eat your fish! Standard nylon is clearly not capable of withstanding the sideways sawing action of triangular teeth. Nor does it greatly resist the determined charges of a 600 lb (270 kg) pinniped predator.

Semi-rigid plastic mesh materials became more widely used in the salmon industry in the late 1990s. While some of these materials led to impressive reductions in sea lion predation (their canine teeth were unable to tear the material), these fiber-reinforced plastics were readily sliced with a knife, and were patently not going to be able to keep Jaws at bay. With their high ratio of net surface area to open area, they were also subject to greater net deflection on farm sites with high currents. None of this boded well for open ocean net pens.

DSM was the first company to recognize and respond to the greater needs of open ocean aquaculture. DSM’s Dyneema® netting – a Kevlar®-like fiber that was developed specifically for marine use – was incredibly strong, and highly resistant to cutting, and - when correctly hung on a rigid-framed net, such that the material was trampoline-taut –was also largely shark-proof. “Largely” however, is not “completely”, and even Dyneema succumbed on occasion, when netting was allowed to ‘bag’. In a few instances, (and remember, you only need a few) sharks on the former Kona Blue Water Farms site showed that if they could get sufficient grip on a hank of Dyneema netting, they could saw and gnaw their way through.

But let’s give credit where it’s due: DSM demonstrated exemplary responsiveness to customer concerns, when these issues were brought to their attention. I very clearly remember my conversation with Ken Robertson, head of DSM’s Sales and Engineering for the Americas, at one of the Aquaculture America trade shows. Ken showed equal measures of empathetic pain and palpable perplexedness to learn of these failings of his mesh.

“We’ll get right on it!” he had said, reassuringly, though I felt anything but reassured. The following year, Ken button-holed me out of the trade show aisle to again assure me that the full weight of DSM’s engineers and material science teams was pursuing a possible solution. I believe that I was less than fulsome in my appreciation of his efforts. (Sorry, Ken… sometimes it’s hard to differentiate earnestness from eager sales talk).

But the following year, there stood Ken, beaming in exaltation in front of a wide-screen video monitor showing some of the most arresting footage I’ve ever seen in aquaculture. It was marketing mastery: shots from an underwater camera of bikini-clad college girls SCUBA-diving through the clear blue Caribbean, interspersed with shots of 6ft-plus bull-sharks tearing frustratedly at experimental cages containing fish carcasses as bait. It was the only time ever – or, at least, the only time that I recall - that such a spectacle of sex and violence graced the Aquaculture America trade show. (Well… apart from the academic sessions on spawning induction in sturgeon).

The reason for Ken’s exaltation was Dyneema’s new Pred-X® material, which consisted of the Dyneema interwoven with a stainless steel wire that served to blunt any shark bite. The bull sharks ended up trashing the cage, breaking the frame and the cradle on which it was perched, but the cobia carcass bait inside and the Pred-X netting both remained intact. I also beamed with Ken, not just because here was a graphic demonstration of a viable solution to a (previously) unsolvable problem, but more so for what it represented: innovation and adaptation and resourcefulness and customer-responsiveness. That powerful convergence of assets and imagination – I could see – was going to be able to be applied to other challenges that we face in our fledgling field.

It was again at a (subsequent) Aquaculture America trade show where I encountered the Wierson family; earnest, honest Oregon folk, with a background in printing and publication, but connections through their church with an American missionary in Japan, who had been asked to test-market a material that Japanese fish farmers had been using for some time, with considerable success. That material – Kikkonet – was comprised of polyethylene terephthalate (PET), which had originally been patented by Du Pont, but then sold to a Japanese company who built a business around corrosion-resistant, high-strength retaining-wall netting, until some fish farmer saw its value. If it can keep boulders off the highway, their thinking went, then it should be able to keep fish in the pen.

At that stage, there was only one example of Kikkonet being used as a net pen outside of Japan. I tracked down the one Aussie barramundi farmer whose farm was sited amongst the mangroves of Far North Queensland (read “crocodile country”). He was reluctant to say too much, but over time offered up the witness: “It saved my farm, mate. It stopped the crocs cold.”

I obtained a hank of Kikkonet as quickly as I could, and offered it up along with a pair of scissors to our company’s Chairman at the next Board meeting. He was determined to cut through the material, to prove me wrong, and ended up trying so hard that he broke the scissors! 

Part of the beauty of Kikkonet (and other rigid net materials) is that if a filament does break, then the rigid net still holds its shape. It doesn’t sag open into an inviting hole that lures curious fish into the outside world. Another beauty of Kikkonet is that it is a monofilament, and so is relatively easy to clean.

The Wiersons have since gone back to the printing business in Oregon, but we should all be grateful for the bridging role that they played. Kikkonet is now sold by AKVA under their brand-name “Econet™.”

What is even better than relatively easy-to-clean predator-resistant net? A predator-proof net that you never have to clean. At the same time that DSM Dyneema and Kikkonet were moving to the fore, the International Copper Association was fomenting their own copper-alloy-chain-link-mesh revolution, aided by member companies in Japan (Mitsubishi), Chile (EcoSea), Germany (Wieland) and the USA (Luvata Appleton), among others. This netting underwent rigorous testing around the globe at numerous farm sites, with some very impressive results.

These materials are robust metal, so predators break teeth before they break-and-enter. And being copper-based, there is virtually no biofouling. No net-cleaning! I’m not sure what fish farmers are supposed to do, then, with all their free time… take up golf? (No, pleeease… not golf!).

We at Kampachi Farms have tested copper alloy materials on an Aquapod™ net pen throughout our experimental Velella Project, and were able to complete an entire grow-out cycle of Seriola rivoliana without either cleaning the net or resorting to therapeutic bath treatments to control the skin fluke ecto-parasites that are the bane of kampachi and hamachi grow-out. Of course, copper is expensive (we sometimes joke that it might be preferable to have gold-plated netting), and it is heavy (which makes the cage design of critical importance). Bekaert from Belgium is now working on a solution to these challenges of weight and cost, with a lighter, duplex stainless steel core mesh, with an electro-plated copper-nickel alloy coating.

In a strange twist, this new copper metal netting now faces challenges with public perception and eco-certification. The Aquaculture Stewardship Council’s salmon standards disallow copper-coated nets, but ASC’s original intention was to discourage use of copper-based antifouling paint on netting, because of the demonstrated, persistent toxicity problems of paint flecks and flakes that dropped to the bottom beneath the net (especially when net cleaning in situ). The International Copper Association has reams of data showing unequivocally that copper metal dissolves slowly in seawater, rather than fragments, and is biologically benign, being dissipated into the water column as copper ions. But the rule – and the misperceptions – will persist until some enterprising fish farmer challenges them both. I trust that it won’t be long.

And nylon nets may themselves be due for a makeover, or a comeback: Intrafish reports that Norwegian netting company Morenot has been testing a plastic coated netting material at 170 Marine Harvest sites in Scotland, with “very good results”.

However, no matter how robust your cage system, or how well-engineered your mooring array, you cannot provide rock-solid assurance to investors, local communities, or environmentalists that there will be no escapes. Even the most robust net pens should be insured against stock losses. While an insurance payout may cover a goodly proportion of the production costs put into the fish, that doesn’t reflect what would have been the fully-realized value of the fish if you had been able to get them to harvest size, and get them to market. And it doesn’t protect your farm or our industry from public pillory. So on many levels we should always, in all ways, fully and fulsomely appreciate the collective creativity of our industry’s engineering partners, and these divergent options for new netting materials that keep moving us forward on our trajectory, pursuing nothing less than perfection.

Onwards! To the horizon, and beyond!

Note: Links to net materials mentioned in the article:






Neil Anthony Sims is co-Founder and CEO of Kampachi Farms, LLC, based in Kona, Hawaii, and in La Paz, Mexico. He’s also the founding President of the Ocean Stewards Institute, and sits on the Steering Committee for the Seriola-Cobia Aquaculture Dialogue and the Technical Advisory Group for the WWF-sponsored Aquaculture Stewardship Council.

Neil Anthony  Sims

Neil Anthony Sims

Neil Anthony Sims is co-Founder and CEO of Kampachi Farms, LLC, based in Kona, Hawaii, and in La Paz, Mexico. Over the past two decades, Sims has led teams that have accomplished a number of breakthrough developments in pearl oyster culture, offshore aquaculture legislation and regulation, marine fish hatchery technology, open ocean mariculture systems, and most recently, untethered open ocean ‘drifter pens’: the Velella project.

Neil is also the founding President of the Ocean Stewards Institute, and sits on the Steering Committee for the Seriola-Cobia Aquaculture Dialogue (SCAD) and the Technical Advisory Group for the WWF-sponsored Aquaculture Stewardship Council. 

Sims resides in Kona, Hawaii.

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