Red swamp crayfish spreads in Israel, raising concern for the Sea of Galilee

The red swamp crayfish, an invasive freshwater crustacean now established in Israel, is drawing concern because of the damage it can cause to ecosystems, agriculture, and water infrastructure. Dr. Dana Milstein, a freshwater ecologist with the Nature and Parks Authority, said the species originally comes from the southern United States and Mexico and is listed among the world’s 100 worst invasive species by the Global Invasive Species Database.

Milstein said the crayfish is highly successful because it tolerates many freshwater habitats, survives low-oxygen water and long dry periods, and can dig deep burrows. It also leaves the water and moves across land on humid nights, helping it spread between ponds and streams. Its rapid growth, high reproductive rate, and broad diet, from plants to small animals, make it especially difficult to control. She said its spread has been driven in part by the aquarium trade, and that Israel and the European Union now ban its trade, possession, or import.

The species harms native life by eating fish larvae, tadpoles, invertebrates, and eggs, stirring up water, destroying aquatic vegetation, and encouraging algal blooms that further reduce oxygen. It also weakens pond and reservoir banks, damages irrigation channels, and hurts farming. The Nature and Parks Authority is working to contain it and, in sensitive sites, eradicate it. Milstein said climate change may help it expand because warming water and drought weaken local species while favoring the crayfish.

In Israel, the crayfish previously became established in Nahal Betzet, where officials had to stop summer water flow to dry out the stream and prevent the population from surviving. After three years of close monitoring, including environmental DNA testing, and no further sign of the crayfish, the intervention was ended and water flow resumed. Milstein warned that if the species reaches the Sea of Galilee, it could quickly disrupt the shallow shoreline, increase turbidity, damage shoreline vegetation, affect fish nursery areas, reduce catches, and interfere with recreation. She also noted a recent surprise discovery of its relative, the marbled crayfish, in a small temporary water body, where a single female likely founded a population through parthenogenesis. She urged the public not to release aquarium animals or aquatic plants into nature and to report unfamiliar species to the Nature and Parks Authority immediately.