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.
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