Helgoland Oyster Hatchery

The Helgoland Oyster Hatchery is an infrastructure at AWI Helgoland, funded and implemented via the PROCEED project. Main goals of the hatchery are to produce seed oysters for native oyster restoration in the North Sea and to address relevant research questions in the field.

The European flat oyster is functionally extinct in the German Bight. Reintroduction and restoration measures are driven under the umbrella of national and international marine conservation measures, funded e.g. by the German Federal Agency for Nature Conservation (BfN). Against the background of active restoration measures in the German Bight, the hatchery will meet the demand for seed oysters in required quality and quantity.

The technical design and management of the Helgoland Oyster Hatchery is based on state-of-the-art knowledge on oyster conditioning and reproduction techniques with the defined goal to produce spat for mid- and large-scale restoration measures in the North Sea. This requires adaptation and optimization of commercial production techniques, which includes a number of applied research topics. Furthermore, the development and compliance of appropriate biosecurity measures for the imported and genetically diverse broodstock oysters as well as for the production of microalgae and seed oysters are important aspects of our work. For more information, see current guidelines on oyster restoration by the Native Oyster Restoration Alliance (NORA).

The research topics addressed within the Helgoland Oyster Hatchery are connected to important parameters for the survival, settlement success and growth of healthy seed oysters. The larval phase is the most fragile one in the oyster’s life cycle: Only ideal conditions allow for successful growth and survival of the larvae. After their planktonic phase, oyster larvae are actively searching for a surface to settle on. Conditioning parameters, nutrient input and contamination treatment are in the focus of current research at the hatchery:

• Optimization of broodstock conditioning, by testing light and density effects in the tanks

• Optimization of sustainable microalgae production, by minimising resource-use and waste 

• Definition of optimal nutrition conditions for juvenile oysters, by testing different (live) feed compositions

• Effects of genetic diversity of hatchery produced oysters on growth and survival in the field (collaboration with CRC Bretagne Nord in France)

• Development of pre-treatment protocols for imported substrate and broodstock oysters to avoid translocation risks

Broodstock oysters are conditioned for reproduction by adjusting diet and ambient temperature. The larvae produced are then carefully raised and supplied with optimal feed. In the last larval phase prior to metamorphosis they are then transferred to settlement tanks, previously equipped with the desired substrate.

In the Helgoland Oyster Hatchery, the optimal rearing of larvae is ensured by a specifically designed water treatment system and state-of-the-art high density larval rearing tanks.

The different life stages of O. edulis are fed with microalgae species (Rhodomonas salina, Isochrysis galbana and Chaetoceros neogracilis), native to the German North Sea around Helgoland. The microalgae production is a crucial part of hatchery production. Here, parameters such as algae growth, algae biomass, biovolume, and contaminations (e.g. protist, ciliates, other algae species) are constantly recorded. When feeding the microalgae to the oysters, the ratio of different species and therefore nutrients is adapted individually to the different life stages.

The settlement substrate is chosen in compliance with the needs of restoration: For the ‘spat-on-shell’ approach, the larvae (spat) settle on European oyster shells; for the ‘spat-on-reef’ approach they settle on reef structures, made of natural materials. In the nursery, they grow on these substrates until they are released at the restoration sites. Once there, they continue to grow and, under favourable conditions, can reproduce in the wild, therefore contributing to the foundation of a new oyster population.

Helgoland Oyster Hatchery works closely with members of the NORA network and in particular with the Production Working Group. This working group aims to find a collaborative solution or common understanding of the barriers to oyster supply for restoration efforts.