A population study of the shrimp Crangon allmanni in the German Bight

Abstract.

The only reproducing population of Crangon allmanni within the German Bight is in the Helgoland Trench (HTR), a depression of more than 50 m depth south of Helgoland. In coastal and shallower offshore waters the shrimp is much rarer and is recorded in higher numbers only in early spring when the water is still cold. The life cycle of the HTR population lasts for about 1.5 years maximum. Recruitment takes place in summer, and these recruits form the reproducing population of the next year. The shrimps are sensitive to environmental stress and are therefore good indicators of environmental changes.