The achievement brings the Machrihanish wrasse hatchery – a joint venture between Marine Harvest and Scottish Sea Farms – closer to its goal of supplying enough of the sea-lice-eating fish to service the companies’ salmon farms in Scotland.
“The wrasse we produce here from our broodstock farms will go to their farms. Hopefully any surplus can be sold to third parties,” hatchery manager Paul Featherstone tells Hatchery International.
The larger aquaculture industry could potentially benefit from the research, says Featherstone. “The research we have done here is for everybody. We have close links with Norway and other hatcheries in Scotland and the information can be disseminated all around the industry. It is a joint industry project and we welcome the opportunity, if need be, to supply larvae to hatcheries.”
Wild ballan wrasse has been used in salmon farms in Scotland for years as a non-chemical way of controlling sea lice infestations. “Obviously, that is not sustainable in the long run. I don’t think it can meet the needs of the expanding salmon industry, that’s why Marine Harvest decided to look at the possibility of farming the ballan wrasse,” says Featherstone.
It took eight years from the launch for the project to achieve the breakthrough. During the first two years, Featherstone and his team were learning the behavior and ecology of wild ballan wrasse that’s necessary for them to spawn naturally in tanks.
Marine Harvest Scotland detailed the challenges on its Facebook page: “As a coastal species that inhabits a reef environment, the behavioural requirements of ballan wrasse are quite significant. As in the sea cages where kelp is required to provide refuge, similar hides and refuges are required in tank sites, where if they are absent, the fish don’t thrive and suffer chronic stress.
“The spawning behavior requires the tank to be set up with a ‘reef’ of kelps and hides, and a spawning ‘sea bed’ area of mats. A harem of females, with fewer males in attendance (similar to red deer), is established. However, in wrasse there is a possible female dominance hierarchy as even though they are all capable, not all females spawn. Also if there are not enough males a female, in time, can change into a male. Wrasse have a rhythmic spawning pattern where they can spawn for four days and not spawn for 10 days, and it is attractive to think that this might be associated with tidal cycles. The very fragile larvae hatch in seven days.”
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“Those fish, which have grown into broodstock, are now spawning for us,” says Featherstone. “So we’ve now completed the whole cycle. Hopefully that would mean that we’d get far better survival and better growth rate and start producing the numbers of farmed wrasse the salmon industry in Scotland requires.”
Featherstone acknowledges more work needs to be done. “We do have our very first farmed ballan wrasse spawning but it is very early days yet and I don’t anticipate a great many larvae this year. However, they have started spawning, the eggs have been fertilised and we have a few of them hatching – this can only improve over the next few years as the fish grow in size and more of them start spawning.”
There are plans to expand the existing facility over the next few years. If all goes according to plan, Featherstone anticipates the hatchery to have capacity to produce 1.5 to 2 million wrasse annually. “I don’t think we can achieve this from the progeny of the wild broodfish we have but I am confident we can with these selected farmed broodstock – and that is the breakthrough.”