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FISH STOCK MONITORING

Drones help researchers check if seabirds get enough fish

Story highlights

  • The rapid development of drones opens up for exciting opportunities even within sustainability science
  • Researchers can, at a very low cost, map abundance and distribution of the seabirds’ prey fish in detail
  • The monitoring is the first long-term study of its kind

Unmanned vessels equipped with echo-sounder makes fish stock monitoring in the Baltic Sea cheaper, easier and kinder to the environment

Low cost, emission free and silent: They are everywhere – in the air, on the ground, on the surface and below water. The rapid development of drones opens up for exciting opportunities even within sustainability science.

Take seabird research in the Baltic Lead for instance.

In a collaboration between the Department for Aquatic Resources at the Swedish Agricultural University and Stockholm Resilience Centre, Jonas Hentati-Sundberg, Olof Olsson and colleagues use a wind-propelled, two meters long unmanned surface vessels (USV) called ‘Sailbuoy’ equipped with an echo-sounder to monitor fish stocks around a large seabird colony.

Replacing ships

Traditional ship-based fish surveys are expensive and resource demanding, and therefore the resolution in time and space is coarse. By using an USV, the researchers can, at a very low cost, map abundance and distribution of the seabirds’ prey fish in detail throughout the entire breeding season.

Moreover, because the USV is wind propelled and solar powered, the operation is totally emission free and silent.

The USV is also designed to ‘survive’ a collision with a ship, a necessary ability in the very busy waters of the Baltic Sea. The instruments onboard are powered by a solar charged battery.

Navigation and simple data transmission are handled through satellite communication, but large amounts of data require monthly memory-stick retrievals.

First of its kind

The island of Stora Karlsö in the Baltic Sea is the home for more than 100 000 seabirds and the main breeding site for Common murres and Razorbills.

During the 2020 breeding season, the Sailbuoy covered 1300 nautical miles (2400 km) within a 5000 square km large area deemed to be a potential feeding ground for the seabirds.

The monitoring is the first long-term study of its kind in the world and is designed to systematically and repeatedly cover the entire area throughout the season to reveal changes in abundance and distribution of the birds’ prey fish, mainly sprat and herring.

This way the researchers can assess how much fish the birds need around the colony to be able to breed and rear chicks successfully.

If we are serious about implementing ecosystem-based management we should make sure that all parts of the ecosystems are considered.

Olof Olsson

In marine environments, this means fish stocks should be managed not only to long-term sustain fishery, but also to sustain the natural predators of these stocks’, such as whales, seals, seabirds and large (predatory) fish.

Next step

During the breeding season, seabirds and seals are restricted where they can feed because they breed ashore and there must be enough fish close to their breeding ground throughout the rearing period.

Hentati-Sundberg says: “Next step in this project is to explore the possibilities to use machine learning and AI to interpret the enormous amount of data that this method generates.”

Published: 2020-12-16

Stockholm Resilience Centre is a collaboration between Stockholm University and the Beijer Institute of Ecological Economics at the Royal Swedish Academy of Sciences

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