Two types of oysters are cultivated in the Netherlands. The flat oyster (Ostrea edulis) which occurs naturally in Dutch waters and the Pacific oyster (Crassostrea gigas) also known as the Zeeland Creuse, which was introduced in the 1960s. The oyster sector has had to contend with various threats, particularly in recent years, including the oyster herpes virus and the oyster drill. In order to prevent predation of oysters by the oyster drill, off-bottom cultivation is used as an alternative by a part of the oyster farmers.
The disadvantages of this are that off-bottom cultivation is expensive and that permits are difficult to obtain, partly because there is often insufficient information concerning the effects of off-bottom cultivation on the environment. Furthermore, there is a lack of factual knowledge on the dynamics of oyster production, loss due to disease and predation. Furthermore, there is no overview of the possibilities to improve yield of bottom cultivation and off-bottom cultivation. Because of the small scale of the oyster sector, there is little capacity to get an insight in these problems and to get a grip on what is needed to improve the efficiency of oyster production.
With this project, we want to support the oyster sector by developing and sharing knowledge, using a combination of experience of the farmers, monitoring and targeted experimental research with optimisation and improvement of the yield of sustainable oyster production as the ultimate goal. The project 'EMFF Yield improvement in oyster production' is a partnership between research (Wageningen Marine Research and HZ University of Applied Sciences) and the oyster sector (Dutch Oyster Association, otherwise known as Nederlandse Oester Vereniging). Together we work on knowledge questions concerning the challenges in oyster farming.
What are the objectives of the project?
- Drawing up a plan of action with regard to yield improvements by recording production and loss figures throughout the production chain and identifying crucial moments and actions in the cultivation process in relation to yield.
- Creating tools to get a better grip on losses caused by the herpes virus and the oyster drill, by monitoring oyster mortality rates.
- Knowledge development to support farming alternatives in other areas (sublittoral) and off-bottom oyster farming in the littoral to promote sustainable cultivation.
Improving knowledge of the production process
By mapping the entire production process of both oyster species, it is possible to identify crucial moments and actions in the cultivation process of oysters. By means of a literature study and interviews with the farmers, fundamental scientific knowledge will be linked to practical experience.
The production process will be made transparent by means of a fact sheet. This fact sheet will describe the production process as well as the general trend of production and loss on the oyster plots during cultivation. These data will be collected by means of a digital log system for the oyster farmers, which will be developed in the project. By carrying out manipulative trials, action perspectives can be drawn up that lead to an improvement in yield in the sector. The effects of timing on the yield (both production and loss) are made clear by drawing up a production calendar.
Monitoring of oyster mortality rates
The combination of the herpes virus and the oyster drill is a major threat to the sector. It is known that mortality is high, but it is unclear what exactly causes high mortality rates. The establishment of realistic mortality figures in relation to both the oyster herpes virus and the oyster drill is included in the plan of approach 2016-2018 (Nov., 2016) but has not been realised to date. Structurally recording mortality through monitoring can provide tools to get a better grip on the threatening factors. It can also help to draw attention to the opportunities and the situation in the oyster sector.
Knowledge development in support of cultivation alternatives
In this section, we focus on knowledge development to support cultivation alternatives in other areas, such as in the sublittoral. In the littoral, it is often difficult to obtain permits due to the possible effects of oyster farming on waders in this area in combination with off-bottom oyster cultivation. Based on an opportunity map, opportunities for both bottom cultivation and off-bottom cultivation in the littoral and sublittoral will be investigated, as well as potentially suitable locations.
For a sustainable development of the oyster sector, knowledge is needed about the effects on the environment. In the littoral, off-bottom cultivation (especially cultivation on tables) can have an effect on the sediment composition and species composition of both benthic animals and birds. In particular, the possible effect of oyster farming on the waders in this area is a subject of interest. The current method for bird monitoring uses wildcams directed at cultivation tables, with photographs taken every 15 minutes. The data processing of this method is very labour-intensive, and there is also room for improvement of the set-up. This project offers the opportunity to acquire the knowledge necessary for appropriate assessments and to reduce the uncertainties surrounding the various cultivation techniques.