Ostrea edulis was once prolific throughout Europe and considered as the continent's native oyster. However, O. edulis currently exists in small fragmented assemblages where natural unaided recovery is rarely encountered. This research identified the small semi-enclosed sea Lough of Strangford on the northeast coast of Northern Ireland as one of the few locations within Europe where the native oyster displayed gregarious natural rejuvenation. On close examination, four influential parameters appeared to assist in concentrated settlement; raised topographical cultch formations, shell coverage, the number of fecund in situ adults, and site protection. If these components were to be combined and managed as part of reintroduction and restoration initiatives, high-density settlements and self-sustaining populations may be possible. The research also identified that unregulated harvesting of intertidal O. edulis assemblages has the potential to seriously hinder natural recoveries. Indeed, the findings suggest that a review of policy in regards to intertidal hand gathering is necessary. However, naturally occurring high-density settlements recorded during this research should be inspirational to all involved in the restoration of the native oyster. Implications for Practice• Examination of naturally occurring native oyster expansion and the parameters which permit augmentation can provide an insight into which components could be implemented to aid successful assisted restoration.• A suite of abiotic and biotic conditions can accommodate mass gregarious Ostrea edulis settlements; hydrodynamics which allow water retention, adequate coverage of suitable substrate, intertidal topography which provides pool structures, in situ resident adults and policing of settlement sites.• Unregulated harvesting remains a constant threat to restoration and protection of the species needs to be implemented if a self-sustaining status is to be achieved.
The marine renewable energy industry is expanding as countries strive to reach climate targets as set out in the Paris Agreement. For tidal energy devices, the potential risk for animals to collide with a device, particularly its moving parts such as rotor blades, is often a major barrier in the consenting process. Theoretical work surrounding collision risk has commonly made use of a formulaic modelling approach. However, whilst providing a platform to assess conventional horizontal axis tidal turbines, the frameworks applied lack the flexibility to incorporate novel device designs or more complex animal movement parameters (e.g. dive trajectories). To demonstrate the novel simulation-based approach to estimating collision probabilities a hypothetical case study was used to demonstrated how the approach can assess the influence that variations in ecological and behavioural data had on collision probabilities. To do this, a tidal kite moving in a 3D figure-of-eight trajectory and a seal-shaped object were modelled and variations to angle of approach, speed and size of the animal were made. To further improve the collision risk estimates, results of the simulations were post-processed by integrating a hypothetical dive profile. The simulations showed how variation in the input parameters and additional post-processing influence collision probabilities. Our results demonstrate the potential for using this simulation-based approach for assessing collision risk, highlighting the flexibility it offers by way of incorporating empirical data or expert elicitation to better inform the modelling process. This framework, where device type, configuration and animal-related parameters can be varied with relative simplicity, on a case-by-case basis, provides a more tailored tool for assessing a diverse range of interactions between marine renewable energy developments and receptors. In providing a robust and transparent quantitative approach to addressing collision risk this flexible approach can better inform the decision-making process and aid progress with respect to developing a renewable energy industry in a sustainable manner. Therefore, the approach outlined has clear applications that are relevant to many stakeholders and can contribute to our ability to ensure we achieve sustainable growth in the marine renewable energy industry as part of a global strategy to combat climate change.
Marine renewables could form a significant part of the green energy mix. However, a potential environmental impact of tidal energy converters (TECs) is collision risk between a device and animal, which has been a significant barrier in the consenting process. While it is important to understand the number of collisions of an animal with the device, the relative speed at which an animal collides with the device, and the point on the animal where collision occurs, will determine whether a collision is fatal, which is important in understanding population-level impacts. Using a simulation-based collision risk model, this paper demonstrates a novel method for producing estimates of mortality. Extracting both the speed and the location of collisions between an animal and TEC, in this instance a seal and horizontal axis turbine, collision speed and location of collision are used to produce probabilities of mortality. To provide a hypothetical example we quantified the speed and position at which a collision occurs to estimate mortality and, using collision position, we determine all predicted collisions with the head of the animal as fatal, for example, whilst deeming other collisions non-fatal. This is the first collision risk model to incorporate speed at the point of contact and the location where the collision occurs on the animal, to estimate the probability of mortality resulting from a collision. The hypothetical scenarios outline how these important variables extracted from the model can be used to predict the proportion of fatal events. This model enables a comprehensive approach that ultimately provides advancements in collision risk modelling for use in the consenting process of TECs. Furthermore, these methods can easily be adapted to other renewable energy devices and receptors, such as wind and birds.
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