Description: The European flat oyster, Ostrea edulis, is a habitat-forming bivalve which was historically widespread throughout Europe. Following its decline due to overfishing, pollution, sedimentation, invasive species, and disease, O. edulis and its beds are now listed as a threatened and/or declining species and habitat by OSPAR. Increasing recognition of the plight of the oyster, alongside rapidly developing restoration techniques and growing interest in marine restoration, has resulted in a recent and rapid growth in habitat restoration efforts. O. edulis seed supply is currently a major bottleneck in scaling up habitat restoration efforts in Europe. O. edulis has been cultured for centuries, however, research into its culture declined following the introduction of the Pacific oyster, Crassostrea gigas to Europe in the early 1970 s. Recent efforts to renew both hatchery and pond production of O. edulis seed for habitat restoration purposes are hampered by restoration project timelines and funding typically being short, or projects not planning appropriately for the timescales required for investment, research-and-development and delivery of oyster seed by commercial producers. Furthermore, funding for restoration is intermittent, making long-term commitments between producers and restoration practitioners difficult. Long-term, strategic investment in research and production are needed to overcome these bottlenecks and meet current ambitious restoration targets across Europe.

Description: The European flat oyster, Ostrea edulis, once formed extensive reef habitats throughout European seas and estuaries. These reefs are now largely functionally extinct, yet interest and support for their restoration is rapidly growing. A major bottleneck to scaling up oyster reef restoration is the lack of available oysters to supply the growing demand. This study aimed to identify the ten questions which, if answered, would increase the consistency and success in hatchery production of O. edulis for habitat restoration. Candidate questions were submitted by representatives from twelve commercial and research hatcheries across Europe. The list of 98 candidate questions were collaboratively discussed by experts from nine research hatcheries across eight countries in Europe, to identify the top ten questions via an iterative and open process. Questions were grouped into the following themes: Conditioning and feeding, larval rearing, disease and water quality, hatchery protocol, genetics, and hatchery management. There were several overarching topics spanning these themes, including diet optimisation, maximising the effective population size, and developing the technical skillbase in order to increase hatchery production to meet the projected increase in demand for oyster seed for habitat restoration efforts. We anticipate this list will provide a starting point for collaborative research efforts across Europe, as well as assisting policy makers and funders in identifying key knowledge gaps.

Description: As part of a research project supported by the European Marine Fishery Fund and the Danish Fisheries Agency (grant no. 33113-I-16-011) and the Danish Centre for Environment and Energy at Aarhus University, field studies were conducted in two different areas of the Limfjorden, in Lovns Bredning (26th February to 4th March 2017) and in Løgstør Bredning (6-10th March 2017). In each sampling area, 16 fixed-position moorings were deployed in two circular sensor arrays around a mussel dredging area to investigate possible effects of dredging related sediment plumes (Pastor et al, 2020). The inner array (stations 1 - 8) had a diameter of 200 m and the outer array (stations 9 - 16) was set up with a diameter of 600 m. Integrated temperature and light loggers (HOBO Pendant Temperature/Light 64K Data Logger) were mounted on each mooring in the two circular arrays at three different water depths (0.5, 1.5 and 3.0 m above seabed). The 48 loggers (3 depths and 16 stations) were deployed in each area over a period of four days and light intensity time series were collected with a sampling interval of 30 seconds. Five loggers in the Lovns area did not provide any data due to technical problems (two near-surface loggers and three loggers at 1.5 m above the seabed). However, only one bottom logger at Løgstør Bredning failed to provide data. Each time series was filtered using a 3-minute moving average for removing the largest outliers, but retaining sharp changes in light intensity associated with short-lived sediment plumes caused by experimental mussel dredging. In addition, a 600 kHz ADCP (RDI Workhorse Sentinel) was deployed at each site (station 1 at the Lovns Bredning mooring, station 3 at the Løgstør Bredning mooring) in a bottom-mounted, upward-looking configuration. 30-second ensembles of 3D velocity components were collected along with corresponding records of beam correlation and error velocity. Each vertical profile had a bin size of 0.5 m and the first bin was at 1.59 m above the bottom (blanking distance: 0.88 m). The velocity data time series at each bin were filtered using a 30 minute moving average.

Description: Field studies were conducted in two different areas of the Limfjorden, in Lovns Bredning (26th February to 4th March 2017) and in Løgstør Bredning (6-10th March 2017). In each sampling area, 16 fixed-position moorings were deployed in two circular sensor arrays around a mussel dredging area to investigate possible effects of dredging related sediment plumes (Pastor et al, 2020). The inner array (stations 1 - 8) had a diameter of 200 m and the outer array (stations 9 - 16) was set up with a diameter of 600 m. Integrated temperature and light loggers (HOBO Pendant Temperature/Light 64K Data Logger) were mounted on each mooring in the two circular arrays at three different water depths (0.5, 1.5 and 3.0 m above seabed). The 48 loggers (3 depths and 16 stations) were deployed in each area over a period of four days and light intensity time series were collected with a sampling interval of 30 seconds. Five loggers in the Lovns area did not provide any data due to technical problems (two near-surface loggers and three loggers at 1.5 m above the seabed). However, only one bottom logger at Løgstør Bredning failed to provide data. Each time series was filtered using a 3-minute moving average for removing the largest outliers, but retaining sharp changes in light intensity associated with short-lived sediment plumes caused by experimental mussel dredging.

Description: Field studies were conducted in two different areas of the Limfjorden, in Lovns Bredning (26th February to 4th March 2017) and in Løgstør Bredning (6-10th March 2017). In each sampling area, 16 fixed-position moorings were deployed in two circular sensor arrays around a mussel dredging area to investigate possible effects of dredging related sediment plumes (Pastor et al, 2020). The inner array (stations 1 - 8) had a diameter of 200 m and the outer array (stations 9 - 16) was set up with a diameter of 600 m. Integrated temperature and light loggers (HOBO Pendant Temperature/Light 64K Data Logger) were mounted on each mooring in the two circular arrays at three different water depths (0.5, 1.5 and 3.0 m above seabed). The 48 loggers (3 depths and 16 stations) were deployed in each area over a period of four days and light intensity time series were collected with a sampling interval of 30 seconds. Five loggers in the Lovns area did not provide any data due to technical problems (two near-surface loggers and three loggers at 1.5 m above the seabed). However, only one bottom logger at Løgstør Bredning failed to provide data. Each time series was filtered using a 3-minute moving average for removing the largest outliers, but retaining sharp changes in light intensity associated with short-lived sediment plumes caused by experimental mussel dredging.

Description: Field studies were conducted in two different areas of the Limfjorden, in Lovns Bredning (26th February to 4th March 2017) and in Løgstør Bredning (6-10th March 2017). In each sampling area, 16 fixed-position moorings were deployed in two circular sensor arrays around a mussel dredging area to investigate possible effects of dredging related sediment plumes (Pastor et al, 2020). The inner array (stations 1 - 8) had a diameter of 200 m and the outer array (stations 9 - 16) was set up with a diameter of 600 m. Integrated temperature and light loggers (HOBO Pendant Temperature/Light 64K Data Logger) were mounted on each mooring in the two circular arrays at three different water depths (0.5, 1.5 and 3.0 m above seabed). The 48 loggers (3 depths and 16 stations) were deployed in each area over a period of four days and light intensity time series were collected with a sampling interval of 30 seconds. Five loggers in the Lovns area did not provide any data due to technical problems (two near-surface loggers and three loggers at 1.5 m above the seabed). However, only one bottom logger at Løgstør Bredning failed to provide data. Each time series was filtered using a 3-minute moving average for removing the largest outliers, but retaining sharp changes in light intensity associated with short-lived sediment plumes caused by experimental mussel dredging.

Description: Field studies were conducted in two different areas of the Limfjorden, in Lovns Bredning (26th February to 4th March 2017) and in Løgstør Bredning (6-10th March 2017). In each sampling area, 16 fixed-position moorings were deployed in two circular sensor arrays around a mussel dredging area to investigate possible effects of dredging related sediment plumes (Pastor et al, 2020). The inner array (stations 1 - 8) had a diameter of 200 m and the outer array (stations 9 - 16) was set up with a diameter of 600 m. Integrated temperature and light loggers (HOBO Pendant Temperature/Light 64K Data Logger) were mounted on each mooring in the two circular arrays at three different water depths (0.5, 1.5 and 3.0 m above seabed). The 48 loggers (3 depths and 16 stations) were deployed in each area over a period of four days and light intensity time series were collected with a sampling interval of 30 seconds. Five loggers in the Lovns area did not provide any data due to technical problems (two near-surface loggers and three loggers at 1.5 m above the seabed). However, only one bottom logger at Løgstør Bredning failed to provide data. Each time series was filtered using a 3-minute moving average for removing the largest outliers, but retaining sharp changes in light intensity associated with short-lived sediment plumes caused by experimental mussel dredging.

Description: Field studies were conducted in two different areas of the Limfjorden, in Lovns Bredning (26th February to 4th March 2017) and in Løgstør Bredning (6-10th March 2017). In each sampling area, 16 fixed-position moorings were deployed in two circular sensor arrays around a mussel dredging area to investigate possible effects of dredging related sediment plumes (Pastor et al, 2020). The inner array (stations 1 - 8) had a diameter of 200 m and the outer array (stations 9 - 16) was set up with a diameter of 600 m. Integrated temperature and light loggers (HOBO Pendant Temperature/Light 64K Data Logger) were mounted on each mooring in the two circular arrays at three different water depths (0.5, 1.5 and 3.0 m above seabed). The 48 loggers (3 depths and 16 stations) were deployed in each area over a period of four days and light intensity time series were collected with a sampling interval of 30 seconds. Five loggers in the Lovns area did not provide any data due to technical problems (two near-surface loggers and three loggers at 1.5 m above the seabed). However, only one bottom logger at Løgstør Bredning failed to provide data. Each time series was filtered using a 3-minute moving average for removing the largest outliers, but retaining sharp changes in light intensity associated with short-lived sediment plumes caused by experimental mussel dredging.

Description: Field studies were conducted in two different areas of the Limfjorden, in Lovns Bredning (26th February to 4th March 2017) and in Løgstør Bredning (6-10th March 2017). In each sampling area, 16 fixed-position moorings were deployed in two circular sensor arrays around a mussel dredging area to investigate possible effects of dredging related sediment plumes (Pastor et al, 2020). The inner array (stations 1 - 8) had a diameter of 200 m and the outer array (stations 9 - 16) was set up with a diameter of 600 m. Integrated temperature and light loggers (HOBO Pendant Temperature/Light 64K Data Logger) were mounted on each mooring in the two circular arrays at three different water depths (0.5, 1.5 and 3.0 m above seabed). The 48 loggers (3 depths and 16 stations) were deployed in each area over a period of four days and light intensity time series were collected with a sampling interval of 30 seconds. Five loggers in the Lovns area did not provide any data due to technical problems (two near-surface loggers and three loggers at 1.5 m above the seabed). However, only one bottom logger at Løgstør Bredning failed to provide data. Each time series was filtered using a 3-minute moving average for removing the largest outliers, but retaining sharp changes in light intensity associated with short-lived sediment plumes caused by experimental mussel dredging.

Description: Field studies were conducted in two different areas of the Limfjorden, in Lovns Bredning (26th February to 4th March 2017) and in Løgstør Bredning (6-10th March 2017). In each sampling area, 16 fixed-position moorings were deployed in two circular sensor arrays around a mussel dredging area to investigate possible effects of dredging related sediment plumes (Pastor et al, 2020). The inner array (stations 1 - 8) had a diameter of 200 m and the outer array (stations 9 - 16) was set up with a diameter of 600 m. Integrated temperature and light loggers (HOBO Pendant Temperature/Light 64K Data Logger) were mounted on each mooring in the two circular arrays at three different water depths (0.5, 1.5 and 3.0 m above seabed). The 48 loggers (3 depths and 16 stations) were deployed in each area over a period of four days and light intensity time series were collected with a sampling interval of 30 seconds. Five loggers in the Lovns area did not provide any data due to technical problems (two near-surface loggers and three loggers at 1.5 m above the seabed). However, only one bottom logger at Løgstør Bredning failed to provide data. Each time series was filtered using a 3-minute moving average for removing the largest outliers, but retaining sharp changes in light intensity associated with short-lived sediment plumes caused by experimental mussel dredging.