Better fish welfare using 'sensor fish'

February 4, 2019, SINTEF

After many decades of salmon farming, recent years have seen studies into fish welfare in connection with issues such as how fish are treated in their cages. In particular, the fish farming sector is looking for better approaches to delousing.

Researchers have now developed an electronic sensor that can be used to measure the external factors that affect fish during processes such as delousing.

The project, Hydrolicerhas, been carried out by researchers to study a mechanical approach to the delousing of farmed fish. The method involves subjecting the fish to turbulence in a water chamber. Currents generated in the water mass effectively "lift" the lice from the fish with no need for chemicals.

"We have progressed from having no idea about what fish are exposed to in terms of mechanical stress to having access to a variety of measurements indicating the types of stresses involved," explains Torfinn Solvang, a research scientist at SINTEF, and manager of the Hydrolicer project.

The researchers discovered that the physical trauma incurred prior to delousing was probably more stressful than the process itself.

"The fish have to be moved from their cages into the delousing chamber using a pump system," says Solvang. "In order to feed the salmon into the pump, they first have to be crowded together so that the system can move fish and not just water. This process can take an hour or more, while the actual delousing is completed in less than thirty seconds," he explains.

The researchers also identified differences between pump systems. So-called ejector pumping, that works using high water pressure, exposed the fish to less physical stress (measured in terms of acceleration) than so-called impeller pumping, which moves the fish using a mechanical paddle installed in the water stream.

The results have encouraged the researchers to start looking for even more data on the stresses that caged fish are exposed to during a variety of operations, not least delousing.

Read more at: