Page 26: of Marine Technology Magazine (April 2011)

26 MTR April 2011 the outer world via the embedded server as described above. The internal communication between the multi- sensor probe and the control unit goes via short range radio. Before measurements the probe is switched on via radio. After measurements the acquired data are down- loaded from the probe to the control unit via short range radio. All control functions including download of meas- ured data can be carried out via the internet according to the instrument web menu. The winch is programmed to take the multisensor probe down to a range of specified depths and then pull the probe back into the buoy for data readout and rest.

Successful automatic long term monitoring of the fish welfare in a fish pen involves satisfactory solutions to three basic problems: 1. Maintenance of the instrument accuracy 2. Satisfactory data communication 3. Automatic data assessment

Biofouling of the sensors is the dominant cause of changes in instrument accuracy when measuring in shal- low depths. Biofouling has been successfully avoided by keeping the multi-sensor probe in darkness and in dry air inside the buoy between measurements. An option for flushing the probe sensors with fresh water after each pro- filing is available but probably not needed.

Both the local communication between the control unit and the multi-sensor probe based on embedded server inside the buoy and the worldwide data communication via the internet has proven to function extremely well. No major problems have been observed.

The multi-sensor probe generates a large amount of data to the connected browser, too much information to be easily evaluated by a typical fish farmer. Therefore in order to make the life easier for the fish farmer and the fish farm owner who may be situated in a foreign country, a dedi- cated expert system for analyzing the data has been

Diagram of the IMR Welfaremeter.