The wild bunch

Wrasse prove a big suc­cess and now they are help­ing ‘train’ their farmed peers

Fish Farmer - - Cleaner Fish – Wester Ross -

DE­PLOY­ING cleaner fish has proven to be a very shrewd move for one of Scot­land’s smaller salmon farm­ers, Wester Ross. The com­pany has not had any sea lice for five years, said farm­ing direc­tor Chris Ford, who spoke to Fish Farmer dur­ing the re­cent Seafood Expo Global in Brussels.

Ford has been in­volved since wrasse were first in­tro­duced at Wester Ross and said to be­gin with they didn’t have much suc­cess.

‘We tend to find that if you put a load of new wrasse out it takes them months and months to get into it, but if you put them in with fish that are used to it, they train them up, it seems.’

The num­ber of ‘trainer fish’ they use de­pends on how many they can keep from cy­cle to cy­cle.

‘If they only had one or two trainer wrasse in the pen that can make a dif­fer­ence be­cause the other wrasse just watch them.’

Wester Ross also feeds the wrasse ev­ery day on a spe­cial diet of nat­u­ral pate, and Ford said they would start at­tack­ing each other if they weren’t fed.

It has been a steep learn­ing curve, dis­cov­er­ing how the dif­fer­ent types of species per­form, and which have the most ef­fect on the lice.

Wester Ross uses wild bal­lan wrasse but also goldsinny, which Ford said has a much bet­ter sur

vi­val rate be­cause they are less ag­gres­sive to each other. They use them when they are short of bal­lan wrasse or if they get dif­fer­ent types of sea lice.

‘The bal­lans def­i­nitely go for the leps (Lepeoph­theirus salmo­nis), which are our main prob­lem. We think the goldsin­nys would take on the cali­gus, the smaller, mo­bile lice.

‘Leps used to be a prob­lem but now we don’t have any. We might get the odd one but we’ve had pretty much zero count for the past five years, since we got over the ini­tial trial with the wrasse.’

The past year has seen ‘re­ally good suc­cess’, said Ford, fol­low­ing ex­per­i­ments us­ing dif­fer­ent types of hides.

‘We tri­alled a few dif­fer­ent things, like us­ing real kelp and stitch­ing it into the ropes and just hav­ing them hang­ing there in the pens.

‘We just have to re­new it ev­ery two weeks be­cause the wrasse eat it all. That seemed to re­ally help them, so we’re ex­plor­ing ways we can ac­tu­ally grow it on to the nets.

‘We’re go­ing to try this sum­mer. I think you can just lay down nets on a kelp bed and lift them up again af­ter a month or so.’

Cur­rently, the kelp they use is picked off the out­side of the preda­tor nets af­ter it has grown dur­ing the sum­mer.

‘They pre­fer this to plas­tic hides and it’s made a big dif­fer­ence in their be­hav­iour- per­for­mance, health and sur­vival.

‘Be­fore, we found they were quite ter­ri­to­rial; if you don’t have enough places from them to hide in then they start at­tack­ing each other. It’s all about keep­ing them as happy as you can and you get a much bet­ter sur­vival rate.’

Wester Ross has an av­er­age of 10,000 salmon per cage and just 22 wrasse in each; it is not ‘about pil­ing the num­bers in, it’s about keep­ing them happy and train­ing them’ said Ford.

“We’ve had pretty much zero count for the past years’” five

‘I think the rea­son we have so much suc­cess is our nets are a bit smaller than the larger com­pa­nies’, so there is more con­tact between the salmon and the wrasse.

‘I think if the big com­pa­nies raised their nets, shal­low them, then the wrasse would have more con­tact. I don’t know if that would nec­es­sar­ily work – they could do it in bursts.

‘We don’t need to do that, it hap­pens nat­u­rally. And as soon as you crowd them up for a har­vest or lice count, you can see straight away the wrasse are in there.’

The wild wrasse are caught in the vicin­ity and the farm­ers can keep them for a whole cy­cle. Dur­ing the fal­low pe­riod, they will dis­card any­thing that’s been dam­aged or is too big.

‘If they’re too big they start at­tack­ing the salmon, they’re pretty hor­ri­ble, they take their eyes out,’ said Ford. ‘It’s more of a size than an age thing – the per­fect size is about four inches.’

He said it is ‘non­sense’ to say wrasse are be­ing fished out in Scot­land, as some have sug­gested, and that salmon farm­ers are us­ing wrasse caught in the south­west of Eng­land.

The stocks are abun­dant and farm­ers such as Wester Ross are strict with the sizes they de­ploy, not too small and not too big. How­ever, the com­pany is tri­alling farmed wrasse for the first time, af­ter in­tro­duc­ing them in March.

‘They’re re­ally quite dif­fi­cult, they won’t eat the pate so we have to get green crab and feed them that,’ said Ford.

They also eat dead fish in the cages and are not yet as ef­fec­tive as the wild caught fish, but they are be­ing closely mon­i­tored.

‘We’re do­ing dif­fer­ent tri­als, so some are in with the wild ones and then we’ve got a cou­ple of cages with them on their own and we’ve no­ticed the lice num­bers are slightly higher. But not many leps, just cali­gus.

‘If it does get to the point where we think it’s too many lice, then we’ll put some trained wrasse in with them.’

The farmed wrasse were sup­plied by Ard­toe which, Ford said, has now dis­con­tin­ued farm­ing wrasse.

‘Even­tu­ally, we’d like this to be a suc­cess, just to pro­tect wild stocks. I don’t think we’re hav­ing a big ef­fect on them any­way. But year af­ter year, you’re bound to have some ef­fect.’

Left: The Wester Ross team in Brussels: Chris Ford, Keith Ber­tram, Barbora Gaborova and man­ag­ing direc­tor Gilpin Bradley. Op­po­site (Clockwise from top left): Wrasse; Chris Ford at a farm site; vis­i­tors to the Wester Ross stand in Brussels; wrasse and salmon.

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