The overall objective of this project is to demonstrate how ecosystem restoration theory can be incorporated within current aquaculture, to increase revenues while minimizing impacts. The specific objective is to assess the feasibility of incorporating oyster reefs restoration with mussel aquaculture.
In this way the restored reef under the culture site will be protected from damages, as no trawling or dredging activities are allowed within the farm, and will be acting as a ‘mother-reef’, providing a source of new seeds, both to replenish natural populations, but also to be collected to start a new chain of oyster farming based on local production, create an economy that promotes local harvests.
This project will investigate the feasibility of restoration of flat oyster, "Ostrea edulis", reefs. The population of this European native species has declined in Europe7 and, in particular, in the Adriatic-Ionian region, due to poorly managed fisheries. The market value of the flat oyster is 3-5 times higher than that of the Pacific oyster9: their reintroduction as a cultivated species in the Adriatic-Ionian region is being successful in Croatia.
This project will be the first step needed to assess the prospect of creating a new oyster market with local seeds, which should not only guarantee a better genetic adaptation to the conditions experienced during culturing (as opposed to importing seeds from different geographical areas as it is currently practiced), but may also carve a new marketing niche.
The methodology to address these specific objectives, is based on system thinking and will involve the development on an integrated model of matter and energy flows within the system composed by: suspended mussel, oysters, sediment and water as well as across its boundaries.
The model will be made up of a set of interconnected modules. While most modules were already built by researchers at the host institution (Ca’ Foscari) during the project two new modules will be developed and tested: growth and energy balance for individual oysters and larval dispersal models to predict population spread.
Furthermore, a comprehensive set of data will be collected at a field pilot site in the Venice area, in order to validate the integrated model. These will include:
- publicly available data sets, collected in routine monitoring activities,
- remotely sensed observations downloaded from the Copernicus Marine Environment Monitoring Service,
- a set of original site-specific field data collected during the project, related to in loco current speeds, temperature, food quality.
Spat collectors specific for oysters harvest will be placed in multiple location accessible by fisheries (e.g. different heights on the poles, surrounding seabed areas..) to identify the best area for collection and spat quality in terms of size uniformity will also be quantified. Natural spat collectors (e.g. shells) will also be placed underneath farming areas and other areas unlikely to be trawled to understand the potential for natural reef restoration. Shells will be reused if possible from restaurants in order to achieve circularity and maximise resources.
"Ostrea" adults acting as seed source are externally sourced from Croatia (northern Adriatic Sea) in order to maintain the Adriatic genetic pool.
Bertolini C and Pastres R., "Identifying knowledge gaps for successful restorative aquaculture of Ostrea edulis: a bibliometric analysis", [version 1; peer review: awaiting peer review], Open Research Europe 2021, 1:103
The first part of the study was a literature review, available from Open Research Europe. The review grouped all research related to Ostrea edulis, both in form of peer reviewed international publication and as local knowledge from library sources. This comprehensive research showed that while restoration studies are recent, evidence for the loss of this species and potential causes (and solutions) have been discussed since the end of the 19th century. While diseases were undoubtedly a leading cause for initial reef loss, coupled with unregulated mass fishery, substratum limitation (given by a loss of seabed complexity, which was also a result of unregulated dredging) appears to be one of the leading limiting factors for both restoration and aquaculture of "O. edulis", and was already mentioned in the early texts that were found in the literature search.