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A revised technique for mapping the spawning sites of Atlantic herring in the UK has been developed which will ensure fish are protected during offshore wind farm construction and which could lead to a more efficient and low cost development process.
 
A new study from the Offshore Renewables Joint industry Programme (ORJIP) funded by Vattenfall, innogy and SSE, led by the Carbon Trust and undertaken by GoBe Consultants, aimed to better understand the location of fish spawning sites in relation to offshore wind farms, and how these are considered within their consenting process.
 
Conditions to manage the effects of noise generated during the construction of offshore wind farms are already incorporated into the consenting process. These restrict construction activities during times when fish are considered to be most sensitive to disturbance, such as during spawning and migration.
The ‘Impacts on Fish from Piling at Offshore Wind Sites’ study, analysed annual fish spawning data in UK waters over the past 10 years to better define fish spawning grounds and to evaluate the potential impacts of new offshore wind sites on fish. The analysis shifts the focus of studies from abandoned spawning sites and highlights those regions that have shown recent spawning activity.
 
The main spawning sites for the different herring stocks in UK waters are well known. However, due to the specific habitat and environmental conditions that herring need to spawn successfully, there are discrete pockets of spawning bed areas that are less easy to identify as they can change from year to year. Currently the exact location of spawning beds can only be identified if they are recorded through grab sampling or by drop down video surveys.
 
As a result, offshore wind developers are affected by both precautionary noise modelling undertaken for environmental assessment, and by precautionary fish sensitivity maps. This means piling activity is often restricted due to limited information available on the actual level of impact risk associated with piling activities.
 
The techniques and methodology demonstrated in the ORJIP study provide clearer information of the areas of spawning and their proximity to offshore wind developments. If considered in the consenting process this could lead to a reduction in construction times, potentially lowering cost to consumers, and reducing  operational disruption for offshore wind farms.
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