Lesotho Highlands trout farmer reaches for the sky with A-HSU® stunning technology
23 December 2025
Sanlei Premium Trout, based on the edge of the Katse Dam in the highlands of Lesotho, has achieved a number of firsts since it began operations seven years ago.
The largest trout farmer in southern Africa, it was the first on the continent to win Best Aquaculture Practices (BAP) certification from the Global Seafood Alliance for its 1,000-tonne capacity farm and hatchery. And now it is the first fish farmer in Africa to adopt in-water humane stunning technology, following the order of an Ace Aquatec A-HSU®, tailored to the requirements of Sanlei’s production process.
The cool, clear waters of the dam provide ideal conditions to rear Sanlei’s premium quality rainbow trout, which are grown in 20x20m square pens with low stocking densities to benefit fish welfare and product quality.
The farm supplies the market in neighbouring South Africa, and has a growing export trade to the US after being appointed supplier to one of the largest American FMCG (fast-moving consumer goods) retailers. Plans to treble annual output to 3,000 tonnes over the next five years prompted the company to seek alternative harvesting methods at the farm.
"Sanlei’s existing pneumatic percussive stunner and manual hand-netting process are bottlenecks for scaling production and meeting BAP certification standards," said CEO Dewald Fourie.
"To meet our expansion targets and to comply with BAP humane slaughter criteria, we needed a solution that not only renders fish unconscious, regardless of size, but simplifies operations by eliminating the need for pre-harvest grading with humane harvesting methods," he said.
"The Ace Aquatec in-water stunner was chosen over percussive methods for its ability to stun all fish sizes without pre-sorting. That makes it extremely user friendly as we have a range of sizing in each pen and now don’t have to grade to a specific size to line up with a specific setting to stun the fish. Also, the fish are 100 per cent unconscious, making them easy to handle without any negative effects."
The trout stunner has also been future proofed. Ace Aquatec Technical Sales Manager Tom Cryans worked with the Sanlei team to deliver a custom designed A-HSU® with an interchangeable inlet to support a phased roll-out. The system is suited to the company’s current needs, with a hopper for hand-netting, and can also accommodate a fish pump, enabling future full automation for a projected increase in production.
"This is going to increase our flow rate significantly, even when we are still hand-netting. Once we start pumping the fish, it will be even quicker, with a throughput of up to 10 to 15 tonnes an hour," said Fourie.
The portable stunner will be mounted next to the pens on a dedicated 10x10m floating steel barge, where all harvest operations will be carried out, with a separate 2x4m barge for the generator. Once the fish are stunned and bled, they will go into ice water tubs for transportation to land. Installation is scheduled for late December, and the system will be fully commissioned by mid-January 2026.
Sanlei – a Japanese word which means ‘where mountains meet the sky’ - is an integrated business with its own primary and secondary processing facility nearby, where fish are filleted and portioned for export. The company is the largest local employer in the Katse community, with 110 people employed, around half of them women, and additional casual labour recruited regularly for busier periods.
In the longer term, Sanlei is looking to expand further, with a second site and total production capacity of around 5,000-6,000 tonnes per year and is already considering a second A-HSU®.
"Working with Ace Aquatec has been an overwhelmingly positive experience," said Fourie. "Their flexibility and attention to detail with regards to our specific operating conditions have made the design of this game-changing technology as smooth as possible. Sanlei is leading the way in southern Africa by implementing more humane practices across our processing operation and the system being installed by Ace Aquatec will support our growth and strengthen our ambitions to further enhance our welfare and certification standards."
Ace Aquatec Chief Sales and Marketing Officer Tara McGregor-Woodhams said: "It has been a pleasure working with Sanlei as they pioneer new quality protocols in the region. The installation in Lesotho marks our first project in Africa and opens a new chapter for Ace Aquatec’s welfare driven technology in the global aquaculture market."
