Processes that put welfare first

Proper and humane harvesting protocols are in the interest of animal welfare and make good business sense, too

Donald Buchanan is Head of Processing with Scottish Sea Farms (SSF). He oversees the company’s two processing and packing centres: Scalloway, which receives fish from SSF’s Shetland and Orkney farms; and South Shian near Oban, which processes fish from the company’s mainland farms. The two facilities employ around a third of the company’s workforce in Scotland and handle the process from harvesting through gutting to packing.

Buchanan says there are three key issues for the processing operations: fish welfare, microbiology and temperature management.

For some time he had been looking for a better approach to harvesting. Automated percussive stunning, which is widely used in the sector, has many advantages but some challenges too, including the need to handle fish of different sizes. For Atlantic salmon, if the average is 5kg, a number of individuals could easily be 3kg or 7kg.

Buchanan says: “Percussive stunning works well on Atlantic salmon of up to 7kg, but once fish grow to 8kg or above the system can become less effective, requiring increased secondary stunning.”

As a farmer used to growing large fish, SSF wanted to explore an alternative method, asking aquaculture technology company Ace Aquatec to look at electrical stunning as an alternative. Using an electrical field to stun fish is not new, however the field needs to be carefully calibrated to avoid distress or damage to the fish.

The system, developed in partnership with SSF, employs a three-step process that includes Ace Aquatec’s Humane Stunner Universal. Harvest-sized fish are transferred from the pens via wellboat to the processing centre. In the boat, oxygen and temperature levels are monitored and the fish are kept in seawater at a low enough temperature to reduce stress and ensure they are near-torpid.

SSF was the first in the Scottish sector to develop a “swim-ashore” system, in which the fish swim into the harvest station via pipes before being dewatered into a closed-loop pipe where they are rendered insensible using an electrical field in the water, without harming them physically.

Some electrical stunning methods use a “dry stun”, where the fish is taken out of the water and stunned on a moving conveyor, but Buchanan explains: “We opted for the ‘wet’ type where the fish are effectively anaesthetised in their own environment.”

The unconscious fish are fed manually into an integrated percussive stunner and bleeder machine. This is the second step in the process, the point at which the main artery is cut and the means of slaughter while the fish are unconscious.

To prevent any undue suffering and ensure full coverage, trained operatives look out for visual confirmation of effective stun and bleed, and will carry out a secondary percussive stun and bleed, if necessary, on a slow-moving conveyor.

Buchanan says: “It is essential that sufficient time is given immediately after stunning and bleeding for operatives to ensure this process has been carried out exactly.”

The slaughtered fish are then transferred to chilled management systems.

Oversight of the harvest process is crucial.

“Our priority is to deliver the highest standards of fish welfare”