15 minute read
The latest fronts on the battle against parasites
Simply
the pest
Sea lice represent a health issue for the industry and a public relations problem – but there are solutions
BY ROBERT OUTRAM
OF all the fi sh health issues in salmon farming, the challenge of sea lice is probably the most conten� ous.
Sea lice not only represent a problem for farmed fi sh, but also – although the extent of the threat is hotly contested – to their wild counterparts. That’s why the “risk-based spa� al framework” published for consulta� on by the Sco� sh Environment Protec� on Agency (SEPA) in December focuses on lice counts and the loca� on of farms away from wild salmon migratory routes.
The issue of sea lice is also a key considera� on for Norway’s “traffi c light” system.
Controlling sea lice numbers is, therefore, a priority for salmon and trout farmers opera� ng marine sites. That’s why, late last year, the MV Coastal Server made the long journey from Norway through the Panama Canal to Bri� sh Columbia on Canada’s west coast.
The Coastal Server, built by Moen Marin for Nidaros Shipping, has been fi � ed out as a specialist delicing vessel, equipped with the SkaMik 1.5 mechanical delicing system. It is the fi rst � me this system has been deployed on the Canadian coast and the Coastal Server will be providing delicing treatment for Grieg Seafood.
SkaMik’s 1.5 delicing system is an improved version of the company’s original SkaMik 1. In tests it has shown that it can remove up to 97% of sea lice at all stages of their development.
Also ac� ve in this market is Smir – the name means “forge” – which supplies complete systems for gentle delousing, as well as semi-enclosed pens. In addi� on, Smir off ers customised prodpens. In addi� on, Smir off ers customised products developed in house, such as water pumps ucts developed in house, such as water pumps and water fi lters.
Smir’s Hydrolicer system is a mechanical, Smir’s Hydrolicer system is a mechanical, non-pharmaceu� cal method for removing sea non-pharmaceu� cal method for removing sea lice from fi sh. The company operates its own lice from fi sh. The company operates its own vessels equipped with delousing equipment. vessels equipped with delousing equipment.
Norwegian company Flatsetsund Engineering Norwegian company Flatsetsund Engineering AS also off ers a mechanical delousing system AS also off ers a mechanical delousing system in the form of the FLS Caligus. The FLS Caligus in the form of the FLS Caligus. The FLS Caligus 250 uses seawater under pressure to fl ush the 250 uses seawater under pressure to fl ush the lice away from the fi sh. The suc� on to li� the lice away from the fi sh. The suc� on to li� the fi sh from the pen operates via a siphon and the whole system is set at a low level above the water in order to minimise the need for li� ing. The pumping ac� on is therefore much gentler and easier on the fi sh – leading, the company says, to much lower mortality rates.
The Caligus 250 typically operates on a pento-pen basis – either transferring the fi sh from one pen to an adjacent pen, or back into the same pen. The delicing system is normally fi � ed on a service vessel – such as the MV Bakkanes, a converted oil industry service vessel
Above: Louse a� ached to salmon Opposite from top: The MV Coastal Server; The Smir Hydrolicer
that is now being deployed at Sco� sh Salmon Company (SSC) sites by SSC’s parent company, Bakkafrost.
As the company’s CEP, Lars Georg Backer, explains, Flatsetsund has now also developed a solu� on for wellboats. While the Caligus 250 uses a pipe with a diameter of 250mm, wellboats now typically use pipes with a 500mm diameter. This makes it more of a challenge to provide an eff ec� ve fl ushing ac� on using the low pressures on which the Caligus operates, but the company has come up with a solu� on in the form of a rectangular adaptor, which is just 250mm from top to bo� om, but wider – about 800mm. This means that the fl ow will be enough to fl ush sea lice away – as with the Caligus 250 – without applying the kind of pressure that might harm the fi sh. The adaptor is similar to that already used for Flatsetsund’s fi sh counter.
Backer adds that a key advantage of the new system over exis� ng delicing systems is that it requires less space on the wellboat. A typical system, for example, needs four lines in order to provide enough capacity to manage a large volume. This takes up a lot of space on the deck, which is typically already full of equipment, while the FLS system uses two lines to process the same volume. The pilot model has a high capacity – 200 to 300 tonnes per hour.
Saving space ma� ers because, as Backer comments: “I’ve never seen a wellboat with a lot of space on it!”
The new FLS model is 6.6 metres x 2 metres, compared with a typical delicing system that could be seven or eight metres long and more than fi ve metres wide.
Fi� ng the delicer on a wellboat means that delousing can be carried out in the course of other opera� ons, such as moving the fi sh, meaning that they only have to be handled once.
Backer says: “If you don’t need to handle the fi sh, then don’t!”
The Flatsetsund design also minimises turns. As far as possible it is straight, again to maximise fi sh welfare.
The pilot study is due to start shortly at FLS’ own site this month and the system will then be trialled with service provider Sølvtrans on one of its vessels.
The new Caligus is expected to be commercially available in May, June or July this year.
Mechanical delicing systems are facing new compe� � on, in Norway at least, from Benchmark Animal Health’s CleanTreat system, which uses a chemical treatment, Ectosan (also known as BMK08, or generically as imidacloprid) to kill sea lice. This is combined with the CleanTreat fi lter system, which prevents the pes� cide from entering the marine environment.
The use of imidacloprid, which is banned for most terrestrial agricultural purposes, has proved controversial. The system has, however, been approved by Norwegian and EU regulators, and has also been awarded the highest level of cer� fi ca� on for sustainability by the Aquaculture Stewardship Council.
Of course, the need for any of these treatments can be signifi cantly reduced if the fi sh can be be� er protected against sea lice in the fi rst place. A variety of closed and semi-closed systems are being or have
applying the kind of pressure that might harm the fi sh. The adaptor is
been developed – for example, the enclosed pens being proposed by
Loch Long Salmon in the company applica� on for a new farm development on Scotland’s west coast.
Farmers using conven� onal pens and cages are also using lice skirts to Farmers using conven� onal pens and cages are also using lice skirts to protect the fi sh. At Tom Morrow, based in Inverness, Scotland, directors protect the fi sh. At Tom Morrow, based in Inverness, Scotland, directors
Marcus Sanctuary, Gary Cunningham and their team have nearly 60 Marcus Sanctuary, Gary Cunningham and their team have nearly 60 years’ experience between them in making lice skirts and treatment years’ experience between them in making lice skirts and treatment tarpaulins. tarpaulins.
Tom Morrow is seeing increased demand from the aquaculture industry Tom Morrow is seeing increased demand from the aquaculture industry for its products as producers con� nue their ever-evolving ba� le with sea «Through dedication, experience and innovative thinking. We strive to beat the lice. The company supplies many producers throughout the aquaculture industry in Scotland and is selling its products to more customers further unbeatable @sealicehunter” afi eld as far away as Canada and Hawaii. The directors stress the importance of their product’s durability: “We say ‘sustainability is key’. Our products last many cycles, save on down � me and money, because of the way they are made. They don’t degrade and they last longer than the compe� � on.
“We can off er the customers what they need, and we are manufacturing these products with our own hands, ensuring integrity and quality is maintained.”
The team at Tom Morrow is also now developing ways to minimise waste through repairing or recycling skirts and tarpaulins. In some cases, even if part of the kit is worn through, there may be other elements that can be reused rather than having to be disposed of.
Meanwhile, Andrew Be� , CEO at Salar Pursuits, believes his business has a low-cost, highly eff ec� ve alterna� ve that can be retrofi � ed into
This page from top: The Caligus delicer; CleanTreat tanks from Benchmark; Smoltscreen lab tests; the SkaMik delicing system
Opposite from top: Tom Morrow Tarpaulins’ high-quality lice fi lter bags on board a vessel exis� ng cages and pens.
The SmoltscreenTM, Salar Pursuits’ lice barrier, is a full enclosure that can be fi � ed inside a pen, preven� ng sea lice from entering but s� ll allowing water – and crucially oxygen – to fl ow in.
The key is Smoltscreen’s woven nylon mesh screen, which at a 150-micron weave is fi ne enough to prevent sea lice larvae – which are no smaller than 180 microns – from passing through even in their earliest stages.
Andrew Be� is a former packaging industry Andrew Be� is a former packaging industry execu� ve who has combined his knowledge of execu� ve who has combined his knowledge of materials and fi ltra� on with his enthusiasm for materials and fi ltra� on with his enthusiasm for wild salmon and his university studies in zoology wild salmon and his university studies in zoology to fi nd a solu� on for the sea lice problem.
The system has been tested under laboratory
condi� ons at the University of S� rling, which demonstrated that the 150-micron weave was enough to keep out nauplius stage sea lice larvae.
Just as importantly, the lab tests also showed that, with a simulated � dal fl ow of 0.58 metres/ second the water in the tank contained enough dissolved oxygen for fi sh thrive without supplementary oxygena� on.
When condi� ons require it, however, the water and oxygen in the Smoltscreen system can be supplemented using two 50hp submersible pumps, Salar says, and they will be working with Sterner Aquatec on the 100 micron drum fi lters for the trial..
The system is now set for trials with smolts at sea in a small 50-metre enclosure at Cashel at sea in a small 50-metre enclosure at Cashel Bay, Connemara, Ireland, from April. Swan Net Bay, Connemara, Ireland, from April. Swan Net Gundry, Killybegs, Donegal will be making the Gundry, Killybegs, Donegal will be making the Smoltscreen enclosure. The trial will be run by Smoltscreen enclosure. The trial will be run by the Marine Ins� tute of Ireland. Be� hopes this will start this April, but the � ming will depend on supply chain issues.
Be� explains: “It’s substan� ally diff erent from a lice skirt – for example, Smoltscreen is a full enclosure, retrofi � ed inside exis� ng salmon cages and closed at the bo� om. Waste can’t be emi� ed and no lice can get in.”
He adds: “The challenge for lice skirts is they compromise oxygen exchange into the salmon cage with every metre of depth. Lice skirts are not easy to clean, having no tensioning at the base, and the diurnal ver� cal movement of the copepod can allow the sea lice larvae to enter the cage underneath even a 15-metre lice skirt.” the cage underneath even a 15-metre lice skirt.”
Be� also argues that lice skirts that do not enclose the whole pen do not provide full protec� on against one sea lice species, Caligus elongatus, which is a parasite feeding on fi sh species that swim at lower depths, such as saithe, cod and lumpfi sh as well as salmonids, which largely stay
Above: Salmon farm with vessel; Checking the salmon for sea lice closer to the surface. The waste – fi sh faeces and uneaten food – can be collected from the bo� om of the enclosure and Be� is working with UCO, the makers of the Foover, a remotely operated vehicle (ROV) originally designed to collected morts from salmon cages. The mesh for Smoltscreen is manufactured by USbased producer Decotex, based in Minnesota and New York. Be� says: “It is a woven nylon, not twisted, so it cleans well and has good tensile strength.” Decotex have suffi cient spare 150 micron mesh capacity for the produc� on of 50 x 150 m Smoltscreen enclosures per annum.
Be� es� mates that by saving the cost of sea lice treatment, farmers using Smoltscreen could a saving of €0.20 per kilo.
Be� is talking to commercial salmon farmers about larger-scale trials. He says: “Our projec� ons for the performance of the Smoltscreen at sea are projec� ons only, at this stage, and we will not be at a commercially proven level un� l peer-reviewed sea trials are completed, hopefully before the autumn of this year. We would welcome any collabora� on on this Marine Ins� tute 50-metre enclosure trial to fully test the concept ahead of salmon farm trials in full-size 150-metre enclosures.”
He also hopes to be able to show that Smoltscreen can also protect against other parasites, hydrozoans (micro-jellyfi sh) and harmful algae.
There is no doubt that the sea lice problem represents probably the most emo� ve weapon for those lobbying against the existence of marine fi sh farms. For example, Salmon & Trout Conserva� on – which campaigns ac� vely against fi sh farming – produces a weekly rundown of “sea lice hot spots” based on the reports required by the Sco� sh Government.
Ac� vist Don Staniford of Scalmon Scotland – formerly known as Scot� sh Salmon Watch – recently published fi gures based on SEPA’s records to show that the use of licenced pes� cide treatments for sea lice doubled between 2018 and 2021. Since 2018, Staniford says, records show 1,735 doses of deltamethrin, azamethiphos and emamec� n benzoate.
The producers’ organisa� on Salmon Scotland responded: “Sea lice management is highly complex and cannot be simplifi ed by aggrega� ng fi gures on medicine use over a narrow � me frame. It’s important to look at the fi gures in their en� rety as longer term trends show that medicine
use varies from year to year, depending on a complex range of factors. “Salmon farmers operate to strict regulatory controls regarding sea lice medicines. These regula� ons are in place to protect the environment and are adhered to across the sector. Informa� on on the use of medicines in salmon farming is publicly available going back to 2002.” And in Canada, the industry has also hit back at cri� cs who claimed that the eff ec� ve removal of salmon farms in the Discovery Islands region north of the Campbell River has led to a 95% reduc� on in reported sea lice among wild salmon. Not so, according to the BC Salmon Farmers Associa� on, which says independently verifi ed data shows that the prevalence of sea lice in the region was low prior to the farms’ removal and has remained so. The report Sea Lice in the Discovery Islands (November 2021) reports the detailed fi gures since a study began in 2017. During the fi ve years of sampling, the average prevalence of fi sh having any mo� le lice (mature lice able to move across the body of a fi sh) was less than 1%. There appeared also to be no increase in sea lice for migra� ng wild salmon a� er their route took them past ac� ve fi sh farms. management is highly complex and cannot be simplifi ed by aggrega� ng It seems that the industry has a ba� le on two fi gures on medicine use over a narrow � me frame. It’s important to look fronts – against the lice and against the claims at the fi gures in their en� rety as longer term trends show that medicine made by its cri� cs. FF
