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Holcim Germany helps relocate European crayfish in disused gravel ponds

Published by , Deputy Editor
World Cement,

In Schleswig-Holstein, Holcim is currently attempting to relocate the European crayfish, which is threatened with extinction, at various disused gravel ponds and thus enable the species to survive in Schleswig-Holstein.

Noble crabs are the largest invertebrates in freshwater and were widespread in Germany and Schleswig-Holstein until a few decades ago. Today, however, most wild populations have almost completely disappeared due to introduced American crayfish and their diseases. The noble crabs also have the highest genetic diversity in Schleswig-Holstein than anywhere else in Germany. Therefore, the state of Schleswig-Holstein is funding this project with funds from the ‘Fish Horizons’ programme. The aim is to preserve the endangered noble crayfish in the wild.

Gravel ponds in particular are important refuges for crayfish, as they find a suitable habitat there with good water quality.

This flagship project is coordinated by the Institute for Sustainable Resource Management. The crayfish are raised in the Oeversee crab breeding facility, and Holcim supported the project with the preselection and provision of the urgently needed bodies of water.

The crayfish released in the Kiesseen originally come from the upper reaches of the Eider. However, invasive American crayfish have spread rapidly there, so that the noble crayfish from the Eider will sooner or later disappear. For this reason, crayfish were taken from the Eider and propagated in the Oeversee crab farm for settlement in the Kiesseen. “It is crucial to find the right body of water for a settlement. Maik Hamann from Holcim was immediately enthusiastic about the project and thanks to the good cooperation, several suitable bodies of water were quickly found and populated with small crayfish,” explains Project Manager, Kai Lehmann.

The development of the animals can be assessed on the basis of the crabs caught. Several well-grown crabs were caught at all locations – the prospects for reproduction in the gravel ponds of Holcim are very good. The largest specimen was over 9 cm long and weighed about 35 g. When they were relocated a year ago, however, the animals were only about 3 cm tall and weighed about 1 g. Looking at the different gravel ponds, however, there are certain differences in the growth of the animals, which are currently attributed to the size of the lake and the different food supply.

If the populations continue to develop so well in 2021, the project partners assume that the noble crayfish will continue to develop independently. To support this, around 3000 animals have again been released into the waters of Holcim. The success of the settlement will be re-evaluated in summer 2021.

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