The Wadden Sea is the nursery ground for brown shrimp. In 1990, a mass invasion of 0-group whiting (Merlangius merlangus) reduced Crangon numbers to almost zero. The 1990 invasion and the decline of the shrimp stock are documented on the basis of surveys that are compared with the years preceding and following. Consequences for the food web in the Wadden Sea and the reasons for the complete recovery of the shrimp stock in each case within one year after its collapse are discussed with regard to the Crangon crangon behaviour and reproductive potential.