The Endemic Oyster Species - Ostrea edulis

The European oyster is considered a keystone species with special ecological function in its typical species community/habitat. Due to its global and regional significance it was recorded in the OSPAR list of threatened species and those deserving protection. Oyster beds are characterized as hot spots of biological diversity: they offer food, protection, substrate for fish and invertebrates and also act as a nursery habitat for many fish species. Overall, oyster beds provide valuable ecosystem services such as increased biodiversity, food and shelter for many species, improved water quality through filtration performance, reduced toxic algal blooms, and consolidated loose of sediments, coastal protection and in sum, an increase in the value of the surrounding ecosystem (ecosystem value).

European oyster stocks are classified throughout Europe as highly endangered. Permanent massive fishing pressure over centuries resulted in a collapse of oyster populations in the course of the 20th century in Europe. In German marine areas there is evidence that originally large oyster stocks have been devastated by overfishing. Those European oyster beds which still exist today are few and scattered: e.g. in Great Britain, Ireland and Denmark.

Feasibility studies and restoration experiments in the UK have shown that rehabilitation measures with oyster beds are based on long term concepts, promising, and the reconstruction of oyster beds is possible.


Restoration of the stocks of the European oyster (Ostrea edulis) in the German North Sea

Within the framework of this research and development project, sponsored by the Federal Agency for Nature Conservation (BfN) and the University of Applied Sciences Bremerhaven, methods and procedures for sustainable stock establishment of the European oyster in the German North Sea will be developed and tested at pilot scale for the first time. As the project RESTORE is based on recommendations of the BfN feasibility study (Gercken & Schmidt 2014) it addresses still open research questions.

The results of this study are intended to create a restoration program, to establish a healthy stock of these highly endangered oysters in Europe and to establish an oyster bed ecosystem at selected locations in the German North Sea.

Project term 2016 – 2019

The reintroduction of the once endemic oyster in the German North Sea is considered a marine conservation measure and is professionally supervised by the Department of Marine Nature Conservation of the BfN and carried out in cooperation with AWI. In order to restore the stock of this species sustainably, nature conservation law must first be review and technological and biological issues overcome to allow final recommendations for a long-term program of restoration.

Scientific and technical objectives

Within the scope of the present research and development project, scientific and technological framework conditions should be created for restoration of European oyster stocks in the German North Sea. While observing nature protection requirements, field studies will be carried out at potential recovery sites to test various technologies for the settlement, growth and fitness of Ostrea edulis.

The following insights are expected:

• Evidence of growth and health (biological fitness)

• Identification of broodstock populations (oysters seeds to reintroduce)

• Recommendations for suitable sites

• Recommendation for appropriate technologies 

First results:

In spring 2017, young spat oysters were spaced deployed in oyster cages in an offshore area north of the island of Helgoland. Juvenile oysters are sampled from the field experiment to gain growth and fitness data. Sampling is carried out by research divers from our research ships FS Heincke, FS Mya II and FK Uthörn

First results show excellent growth rates and a good overall health status of the former native oysters. Since autumn 2017, the current experiment has been extended by a further location in the research field MarGate Helgoland. 


Did you know?

Due to their important ecological properties, Karl Möbius introduced the term Biocoenosis 1877 based on the oyster beds

Interesting facts about the oyster

Scientific name:  Ostrea edulis
Common name: European oyster (German name: Europäische Auster)
Size: 12 to 20 centimeters
Age at sexual maturity: 3-4 years
Distribution area: Atlantic Ocean from Norwegen to Portugal and the Mediterranean. In Germany and Belgium the species is considered extinct
Habitat:            low water line to a depth of 40 meters
Biology: the free floating oyster larvae settle after a few days to a few weeks.  Once they settle and become established on appropriate hard substrates (preferential oyster and mussel shells), they remain as sessile organisms there
Diet: plankton organisms filtered from seawater