Abstract
The waters around Wales are home to a diverse range of habitats and species of national and international importance. They also contain a rich renewable energy resource with up to 6 GW of generating capacity potential for wave and tidal stream energy. Wales is well positioned to play a leading role in these emerging sectors; however, it is important that the sectors develop in a way that is both economically feasible and environmentally sensitive. A recently published report – ‘Review of Monitoring Methodologies and Technologies Suitable for use in High Energy Environments in Welsh waters’ 1 , suggested merit in gathering strategic evidence for key marine features (marine mammals, birds and fish) to support the tidal stream sector. In response, the Welsh Government has commissioned The Centre for Environment, Fisheries and Aquaculture Science (Cefas) to provide advice on the value of surveys for new strategic evidence on migratory fish, marine mammals, and diving seabirds in relation to tidal stream resource areas around Wales.
The advice, presented in this report will help to inform understanding of the need for, and practical considerations related to, potential surveys for strategic evidence which can support the sustainable growth of the tidal stream sector. The project had four objectives:
- Objective 1: What could strategic survey evidence tell us?
- Objective 2: Which methods work where?
- Objective 3: How many data are needed and what would they cost?
- Objective 4: Making strategic evidence available.
Strategic evidence in this case is defined as information on the presence, abundance, distribution, and also behaviour of the animals in and around tidal energy resource areas (RAs). For the strategic evidence to be useful it should be relevant to two areas. Firstly, it should support the overall planning and consenting processes of a developing tidal energy sector. Secondly, it should help fill some known scientific evidence gaps on the effects of tidal energy devices on marine animals.
Evidence gaps on tidal energy have been identified by Offshore Renewables Joint Industry Programme – Ocean Energy (ORJIP-OE2 ). It was determined that strategic evidence could help fill many of these gaps, either completely or partly.
The Review of Monitoring Methodologies and Technologies Suitable for use in High Energy Environments in Welsh waters identified methodologies for collecting suitable data on migratory fish, marine mammals, and diving seabirds. The ability of each methodology to provide useful strategic evidence versus the costs and risks were examined. The findings in this report are largely comparable with the previous study, although it was recommended that Passive Acoustic Monitoring (PAM) methods should be considered further. For migratory fish, Environmental DNA (eDNA) and arrays of acoustical tracking devices are most likely to provide useful data. For marine mammals and diving seabirds a combination of visual surveys from boats and land would be most useful and cost effective. For marine mammals PAM would also be very useful at filling gaps in visual surveys. Visual surveys and PAM for marine mammals and seabirds are tried and tested methods with low risk, albeit high cost.
Before any new surveys for strategic evidence are planned it is important to consider what the objective of the strategic evidence would be. In simple terms: what is the scientific question that strategic evidence is trying to answer? Once the objective of the strategic evidence has been defined, the next step is to determine what information is needed to meet this objective. In many cases it may be possible to use existing data as part of this information. It may also be necessary to collect new data to fill in the gaps.
Overarching strategic evidence objectives for each key feature relevant to each stage of the planning process were suggested. The existing data on each key feature was examined before recommendations on where new data would be needed were made. The review concluded that there are very few existing data on migratory fish in the marine area. For marine mammals and diving sea birds there are good data already available which could be sufficient for planning and policy. But in all cases, there are insufficient data to fill the current evidence needs in either consenting or scientific gaps.
For migratory fish, any new strategic evidence would be useful. There are, however, no guidelines or established methods on how many data should be collected and therefore this needs to be considered in planning strategic surveys. For marine mammals and diving seabirds, monthly surveys for a minimum of two years were recommended. This is in line with industry guidelines for offshore renewable energy developments.
A range of options were considered for survey work that should provide useful strategic evidence. For each option, the indicative costs, the risks of not being able to provide sufficient data, and the benefit of the data to the tidal sector were taken into account. These options are summarised in the table below.
Any work involving the use of boats and equipment such as acoustic recorders will have a high cost. However, savings can be made if boat surveys are combined (boat costs usually being the most significant). Due to the methodologies being relatively novel, and logistical issues in capturing and tagging rare fish, all migratory fish options are considered high risk. In contrast, the methods for surveying marine mammals and diving seabirds are tried and tested across numerous commercial projects and are therefore, much lower risk. In all cases the benefit of new strategic evidence to the tidal sector is proportional to the scale of the survey work.
A programme of strategic surveys will only be useful if the data are accessible to those who need them. A number of recommendations on data standardisation, storage and publication of metadata are made. Considering these factors from the beginning will pay dividends and help avoid unforeseen costs.
Overall, this advice concludes that monthly surveys for marine mammals and diving seabirds are likely to be useful across multiple areas of the planning and consenting processes and to address evidence gaps.
The main concern for migratory fish is that of collision risk causing population level impacts. However, this risk is a perceived risk rather than a proven risk. If this risk is not realised, then value of surveying for migratory fish is reduced. The very high cost of tagging studies versus the real risk of collecting insufficient data is of concern. For this reason it is recommended that the acoustic tagging arrays options are considered as research proposals at this stage and warrant further discussion. eDNA studies would be useful and in contrast to tagging studies are relatively low cost. While it is not recommended to carry out eDNA studies on their own, combining the work with marine mammal and or seabird surveys could be cost-effective.
The next steps from this project would be to consider which, if any, options could be taken forward. Any options progressed will need to be planned and costed in detail, bringing in the relevant scientific and fieldwork experience. The benefits of this include pooling expertise on data processing, ensuring suitable statistical power and maximising efficiencies.
Finally, the report recommends that any strategic evidence programme is centrally coordinated in Wales. Centralising the objective setting, the survey planning, and the data coordination is likely to be the most impactful action to support a developing sustainable tidal sector. The cost of strategic coordination is minimal, but the benefits would be felt by all.