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