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Since 2015, biologist Lonneke IJsseldijk has been researching stranded porpoises on behalf of the ministry of Agriculture, Fisheries, Food Security and Nature. Not only to better understand the animal but also to monitor the ecosystem.

The porpoise sits on top of the food chain.. This seems favourable, but has its own risks. Substances such as PCBs and PFAS accumulate in animals. “The higher an animal is in the food chain, the more these harmful substances assimilate. They are the canaries in the coal mines” says IJsseldijk.

In addition to the porpoise, IJsseldijk also studies the white-beaked dolphin. “We are seeing fewer of them,it seems the common dolphin is taking their place. We suspect that they’ve shifted northwards due to the warming of the ocean. The white-beaked dolphin prefers colder water, while the common dolphin prefers warmer water. The species composition in the North Sea is changing due to climate change.”

The porpoise acts as a canary in the coal mines

The health of the porpoise also provides insights in the spreading of pathogens as well. For example, bird flu is becoming more and more common with marine animals. “This indicates a change in the infection pattern and makes it clear that there’s a broader ecosystem problem.”

“Our biggest challenge is proving the connection between cause of death and its impact on the population”, says IJsseldijk. “On the dissection table I can see a porpoise that is severely emaciated, but the cause is often unclear. The habitat may be disrupted by climate change or the construction of wind farms. Establishing this connection is difficult. We need a large database to conduct analyses. The bigger the database, the more connections we can make in the future.”

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