First things first: before you get excited about cute otter GIFs, the “otter” here is actually a two-metre robot boat.

Based at NTNU — the Norwegian University of Science and Technology — the NTNU Fish Otter project employs four Raspberry Pi 4-controlled autonomous catamarans. These vessels are what they call Fish Otters. The Otters are designed to track acoustic fish tags beneath the water’s surface.

How do you tag and track a fish?

Fish tags are tiny sound-emitting devices that are attached to fish. Researchers and conservationists either implant the tags into fish, feed them to the fish, inject them, or attach them to the outside of larger fish.

The goal of the project is to perform persistent tracking of fish locations by combining sensor readings from multiple vessels. The time it takes for a fish tag’s signal to reach a receiver depends on how far the signal has to travel. From the differences between the arrival times of a signal at different receivers, you can work out the differences between the distances from the tag to the various receivers. From these, together with the locations of the vessels, you can work out the location of the tag.

What kind of vessel is an Otter?

Otters are small uncrewed catamaran-style boats propelled by two fixed electrical thrusters. And by small, I mean the footprint of the whole vehicle is just 200cm x 108cm x 81.5cm. They weigh just 55kg.

The vessel design is based around the hull, thrusters, and power distribution of a Maritime Robotics Otter, but with new sensors and control systems designed at the NTNU.

The Raspberry Pi computers on the Otters are running Raspberry Pi OS Lite with a customised version of the DUNE Unified Navigation Environment. Team members chose Raspberry Pi OS because of “the great amount of community support available”, as well as their previous experience using it.

If only Nemo had been tagged. That would have been a very different film. No need for that awful shark Bruce to show up and haunt my dreams for ever more.

We enjoy seeing life science researchers adopt Raspberry Pi hardware, both in the lab and in the field. We were very pleased to see a review of these applications from Jolle Jolles, a behavioural ecologist, last year. Take a look to see the wide variety of biological science research where our computers have a supporting role.