Fish and sealife in the Oosterschelde has fallen considerably in numbers

Things are heading in the wrong direction for various characteristic fish and benthos animals in the Oosterschelde, like mussels, plaice, and lobsters. On average, animal populations monitored there have declined by 28 percent over the past 30 years, Statistics Netherlands calculated.

The statistics agency analyzed research data provided by The ANEMOON Foundation, who keep an eye on 37 different types of sea life creatures. Of these, 15 have been reduced in numbers.

However, positive developments were reported regarding animal types that swim in the estuary in Zeeland or crawl between the basalt blocks that have been used to reinforce the dikes. The number of eight types of animals increased during the study. The flat oyster and the purple snail were examples of this. The other ten monitored animal types were stable.

The Oosterschelde has a protected status as a Natura 2000 area. It is also a National Park. There have been concerns regarding the reduction of lobsters and mussels in Zeeland for a while.

Fishermen and nature conservationists believe there is a connection with the dumping of steel slag, a residual product of the steel industry, near the dikes. However, scientific research has not yet been able to provide a definitive answer to the cause of the decline.

Statistics Netherlands pointed out that crustaceans are dependent on gaps between the basalt blocks. The animals "find them less easily because they are being filled with steel slag,” so that may play a role in the decline.

When it comes to the reduction of fish, the increasingly hot climate plays a significant role in the reduction. The water in the Oosterschelde is becoming hotter. Fish who are more suited to colder water are, therefore, moving to deeper waters in the North Sea.

More and more exotic species are living in the Oosterschelde, species that do not naturally belong there. They are often brought in via international ships but also come as a result of climate change. European animal types that used to be seen in the south of the continent are moving more towards the north.

“Several exotic species are now widely present, like the Japanese oyster, squid, and American comb jellyfish,” Statistics Netherlands said. Although the emphasis on exotic species is usually on the disadvantages they have for native species, there are sometimes also positive effects. For example, Japanese oysters form a suitable substrate for other bottom animals to settle on.