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Die Zahl großer Süßwassertiere wie Störe, Riesenwelse, Flussdelfine, Flusspferde, Krokodile oder große Schildkröten ist weltweit stark zurückgegangen, ebenso wie die Größe ihrer Verbreitungsgebiete. Die Ursachen für die Gefährdung dieser Megafauna sind weitgehend bekannt, die Folgen des Verlusts für die Ökosysteme dagegen kaum.

The striped marlin is one of the largest and fastest predatory fish in the ocean. This  species forms groups when hunting schools of small fish, aided by its long, spear-like rostrum. A study by the Cluster of Excellence “Science of Intelligence“ (SCIoI) with Humboldt-Universität zu Berlin and IGB now explains how the fish might coordinate the rapid sequence of their attacks without injuring each other. The key to this, they suggest, is rapid colour changes - like a traffic light. Bright body stripes signalise: "Now it's my turn to hunt".

Native fish species in the upper Danube River Basin have been particularly sensitive to changes in flow regimes in the past, while higher temperatures will pose the greatest threat in the future. The threat assessment will remain at least as high in the future. However, it could probably be mitigated by reconnecting former floodplains and improving river connectivity. 

The contraceptive pill is obviously not intended for fish and frogs. However, the hormones in the pill and other pharmaceuticals that are not completely broken down in sewage treatment plants can affect aquatic organisms. This is because the human hormone system is not so different from that of other vertebrates. In fact, the same transmitters and receptors are often involved. The World Health Organisation (WHO) calls these substances or their mixtures endocrine disruptors, and there are regulations to assess and reduce the risk to humans and animals.

The EU Nature Restoration Law (NRL) awaits its formal adoption within the next weeks. Amongst other goals, the NRL aims to restore 25,000 km of free-flowing rivers by 2030. The NRL represents an important opportunity for the restoration and safeguarding of European rivers, its biodiversity and ecosystem services they provide to people. However, seven central challenges must be anticipated in its implementation, which may compromise its success. 

The flood situation in parts of Germany is slowly easing. It can be expected that after some weeks the rivers will have returned to their beds. But how wide is a natural riverbed? Under what conditions does flooding become dangerous for us – and is it also dangerous for nature? How can we better prepare for such extreme events and which measures are beneficial for both people and nature? The current flood events make it clear that we need to rethink flood protection.

The Red List of freshwater fish and lampreys in Germany has been updated for the first time since 2009. It shows a clear negative trend over the last 14 years: 21 species have been classified threatened. This means that more than half of the native species are now considered threatened or already extinct. With 10 per cent of fish species extinct, Germany is well above the European average of 2.5 per cent.

Clonal fish that are reared under nearly identical, highly standardised environments systematically differ in the number and size of offspring per reproduction cycle, two crucial indicators of biological fitness.