The European flat oyster Ostrea edulis has been harvested for centuries but production continues to be significantly affected by stress and diseases impacting oyster growth and survival. Whilst production remains active in some areas, supplying a high-value product to a niche market, cultivation practices continue to be adapted to meet the demand. These include exploring sites further away from the shore as well as the potential for co-cultivation with other species groups such as shellfish and seaweeds.
This study explores the feasibility of growing oysters subtidally at an existing seaweed cultivation site in comparison to a traditional intertidal oyster monoculture. Juvenile O. edulis were deployed in baskets at either site and monitored for two years (Nov 2020 – Oct 2022) for their progression in growth, survival, and marketability (meat yield and condition index), respectively. Ultimately, the shelf life of the harvest-size oysters was determined, and sites tested for the presence/absence of the diseases-causing Bonamia ostreae using a qPCR approach.
Oyster growth was rapid in the first year of culture and progressively slowed, following different seasonal dynamics and average growth in shell height of 1.09 and 1.55mm mth_1 in intertidal and subtidal culture, respectively. Meat yield and condition index varied throughout the study period and with season, being highest in early Summer and lowest in late Winter, and coinciding with the seasonality in oyster reproduction and environmental conditions (water temperature, food availability).
Most notably however, oyster survival differed dramatically across sites and seasons with re-occurring mass mortalities during hotter summer months at the intertidal but not the subtidal site. With mortality rates exceeding 70% compared to 1% in subtidal culture, and without confirmed presence of B. ostreae at either site, O. edulis appears to perform better in subtidal (i.e., suspended) culture.
This study provides long-term multi-parameter data on the conditions and performance of O. edulis in commercial culture. Our findings highlight that suspended culture can improve overall performance and most importantly survival, providing new opportunities for exploration of mono- as well as co-cultivation operations offshore.
comparative growth, PErformance and survival of the european flat oyster Ostrea edulis in intertidal and subtidal cultivation
Michalek K*1 , Macleod AKA1 , Bean TP2 , Stanley MS1
1The Scottish Association for Marine Science (SAMS), PA37 1QA Oban, Scotland, UK
2 The Royal Institute, University of Edinburgh, EH 25 9RG Midlothian, Scotland, UK
Corresponding author : kati.michalek@sams.ac.uk
The European flat oyster Ostrea edulis has been harvested for centuries but p roduction continues to be significantly affected by stress and diseases impacting oyster growth and survival . Whilst production remains active in some areas, supplying a high-value product to a niche market , cultivation practices continue to be adapted to meet the demand. These include exploring sites further away from the shore as well as the potential for co-cultivation with other species groups such as shellfish and seaweeds.
This study explores the feasibility of growing oysters subtidally at an existing seaweed cultivation site in comparison to a traditional intertidal oyster monoculture . Juvenile O. edulis were deployed in baskets at either site and monitored for two years (Nov 2020 – Oct 2022) for their progression in growth, survival, and marketability ( meat yield and condition index), respectively . Ultimately, the shelf life of the harvest-size oysters was determined, and sites tested for the presence/absence of the diseases-causing Bonamia ostreae using a qPCR approach .
Oyster growth was rapid in the first year of culture and progressively slowed , following different seasonal dynamics and average growth in shell height of 1.09 and 1.55mm mth
1 in intertidal and subtidal culture , respectively. M eat yield and condition index varied throughout the study period and with season, being highest in early Summer and lowest in late Winter , and coinciding with the seasonality i n oyster reproduction and environmental conditions (water temperature , food availability).
Most notably however , oyster survival differed dramatically across sites and seasons with re-occurring mass mortalities during hotter summer months at the intertidal but not the subtidal site . With m ortality rates exceeding 70% compared to 1% in subtidal culture, and without confirmed presence of B. ostreae at either site , O. edulis appears to perform better in subtidal (i.e., suspended) culture.
This study provides long-term multi-parameter data on the conditions and performance of O. edulis in commercial culture. Our findings highlight that suspended culture can improve overall performance and most importantly survival, providing new opportunities for exploration of mono- as well as co-cultivation operations offshore.