Measuring fish welfare online

Photo by Frank Gregersen, Fiskeriforskning ©

New technology developed within RTD pillar 5, project ETHIQUAL makes it possible to measure whether the fish are thriving in the fish farm. A small apparatus on the fish registers its breathing activity, showing whether it is doing well or is stressed.


Authors: Øyvind Aas-Hansen, Børge Damsgård, Hilde Toften and Frank Gregersen, Fiskeriforskning (Norwegian Institute of Fisheries and Aquaculture Research).






The possibility of documenting the well-being of the fish is becoming more important in line with increased emphasis on animal welfare. Traditionally, a number of individual factors are measured to monitor the well-being of farmed fish, such as density of fish in the net cage, the oxygen level in the water and the amount of waste products. This does not take into account how the sum of all the factors affects the fish. Also, only a few known factors are measured. As part of RTD 5, project 5.2 ETHIQUAL, a new concept has been developed which measure how the total effect of the farming environment affects the welfare of free-swimming fish in aquaculture.

Left: While the cod is anaesthetised, the equipment is attached. Here, the plastic hose which is fastened inside the oral cavity, is going to be connected to the tag on its back.
Photo by Frank Gregersen, Fiskeriforskning ©

The equipment, called SmartTag, is attached to the fish and measures how often and how much the pressure changes in the mouth, and with that, the breath of the fish. From the tag, audio signals are sent to an under-water microphone, forwarding it to a computer where a programme calculates the breathing activity. Previous and ongoing laboratory studies have demonstrated that breathing activity is a good welfare indicator in fish, responding both to variation in water quality and to other types of stress factors.

Transmitters attached to the fish have been used for many years, e.g. to map where the fish swims. But measuring the well-being of the fish is a new use. We envisage that in the future, fish farmers can monitor their fish by having a certain number with this equipment in the net cages. Abnormal breathing activity indicates something is wrong, and measures can be implemented. So far, successful testing of the equipment for use on cod has been carried out at Fiskeriforskning this autumn. The technology will initially be used in SEAFOODplus research work on cod and sea bass in Norway and France, respectively.

The SmartTag prototypes were developed for SEAFOODplus by the technology company Thelma ( in Trondheim, Norway.


Computer screenshot showing online recordings of breathing activity of a free-swimming cod. When the cod breathes, the pressure-changes inside its mouth are detected by the tag and sent to a computer for processing. Photo by Øyvind Aas-Hansen, Fiskeriforskning ©