Sea lice infestations are a common problem in salmon farms, and while there are chemical-free ways of getting the parasites off the fish, they're kind of rough. A new device is being put through one such delousing process, in order to measure just how hard it is on the salmon.
Frequently, in order to treat the fish for lice without using toxic substances, salmon are moved from their pens into a delousing chamber called a hydrolicer, where artificially-created currents create turbulence that lift the parasites off the skin. A new Norwegian project is aimed at identifying possible detrimental effects of the treatment.
To that end, a team from the SINTEF research group has been utilizing a "sensor fish" that gets sent through the process along with actual salmon. Measuring about 50 cm long (19.7 in), the cylindrical device contains sensors that monitor factors such as temperature, water pressure, light conditions, acceleration and elapsed time. An integrated microprocessor records and analyzes all the measurements, allowing researchers to determine how much mechanical stress is being placed on the fish.
So far, it's been found that the one-hour process of getting the fish into the hydrolicer is actually more arduous than the 30-second treatment itself. That's because it typically involves first crowding all the fish together so that they're easier to catch, then using a pump to suck each one from their pen into the delousing chamber.
That said, the sensor fish is so far unable to determine how much psychological and physiological stress the salmon experience. "The next step is to measure fish heart rhythms," says SINTEF's Ulf Gøran Erikson. "Only then can we arrive at some conclusions about how fish really respond to the various delousing methods."
A smaller but similar device, also called the Sensor Fish, has previously been used by the US-based Pacific Northwest National Laboratory to measure how the presence of hydroelectric dams affects migrating salmon.
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