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New Electronic “Sensor” Fish Measures the External Factors that Affect Fish During Delousing

Following several decades of salmon farming, in recent years, there has been a growing interest in research into fish welfare with regards to problems like how fishes are treated in their cages. Specifically, the fish farming sector is seeking better methods for delousing.

How is it actually a farmed salmon? Measurements from the sensor fish experiments give new answers to it. One of the goals is to further develop more gentle methods for debugging and handling the fish. (Image credit: Thinkstock)

Scientists have currently created an electronic “sensor” fish that can be used to measure the external factors that impact fish during processes like delousing.

Scientists have conducted the project Hydrolicer to examine a mechanical approach to the delousing of farmed fish. In this approach, the fish is subjected to turbulence in a water chamber. Currents created in the water mass effectively “lift” the lice from the fish without requiring 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.

Torfinn Solvang, Research Scientist, SINTEF

Solvang is also the manager of the Hydrolicer project

Scientists found that the physical trauma suffered before delousing was perhaps more stressful when compared to 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 describes.

Furthermore, the scientists identified differences between pump systems. The purported ejector pumping, which functions using high water pressures, subjected the fish to less physical stress (measured in terms of acceleration) when compared to so-called impeller pumping, which involves moving the fish using a mechanical paddle set up in the water stream.

The results have inspired the scientists to start seeking even more data on the stresses experienced by caged fish during a range of operations, particularly, delousing

Do Fish Feel Pain?

Researcher Ulf Gøran Erikson who was originally trained as a chemist also works with farmed fish. He has been a keen observer of improvements in the industry for several years and has worked a lot with veterinarians on many of his research projects.

According to him, there is an increasing volume of study signifying that fish can feel pain, although until now this has proved challenging to measure.

We’ve sent everything from vegetables to plastic bottles through the pump systems. However, unlike the fish, neither vegetables nor the “sensor” fish are competent swimmers with the ability to position themselves intelligently. So it will be interesting to see if we can identify new methods of finding out how fish actually respond to various types of handling.

Ulf Gøran Erikson, Researcher, SINTEF

Erikson is also working on the Hydrolicer project.

Keeping all this in mind, Walter Caharija, a cyberneticist and researcher, has been taking a closer look at what happens to the fish at the time of the delousing process.

Currently, some of his findings are available as part of the Kvalisys project. The aim of this project is to promote the development of the sensor fish to acquire even more data related to fish welfare.

The “sensor” fish is a cartridge-shaped object with a length of around 50 cm, comprising a small computer and electronic instruments, and is designed to measure the responses of the fish surrounding it.

Think of a big tube through which the fish are pumped from the inlet of one cage to the outlet of another. The instruments in the “sensor” fish instruments record temperature, pressure, and acceleration and, not least, how the sensor responds to the time it spends in the pump system.

Walter Caharija, Cyberneticist and Researcher, SINTEF

In collaboration with the scientists at the Hydrolicer project, Caharija has devised a method designed to uncover even more information about fish welfare and more importantly the relationships between how mechanical stress, technology, and biological factors affect the fish.

Hence, the “sensor” fish is fitted with a range of instruments to measure water pressure, acceleration, temperature, and light conditions. It has a surface sensitive to pressure and is equipped with a GPS tracker.

Measurements carried out during the “sensor” fish experiments are opening new doors to scientists to further develop more sensitive delousing techniques, which are highly preferred within the aquaculture sector mainly since fish welfare is now turning out to be more and more significant at all stages of the value chain. This hasn’t been the case always.

Ten years ago, and before that, there weren’t as many inspections. Today, however, fish welfare is one of the most important priorities in the fish farming sector.

Ulf Gøran Erikson, Researcher, SINTEF

Next Step—Measuring Stress

Erikson highlights that they have not evaluated all delousing techniques which are employed at present and that the “sensor” fish cannot help to fulfill all the issues related to fish welfare.

We’re talking about mechanical stress,” says Solvang. “The ‘sensor’ fish can’t tell us anything about stress levels in fish—our electronics simply cannot measure this. At least not at the moment,” he smiles knowingly.

Erikson and Solvang declared to Gemini that new projects are being started to study several aspects of fish physiology.

The next step is to measure fish heart rhythms. Only then can we arrive at some conclusions about how fish really respond to the various delousing methods,” concludes Erikson.

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