Exploring Underwater Scilly: Monitoring Marine Protected Areas Using Cutting-edge Underwater Cameras

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In one of the largest surveys of a UK marine protected area (MPA) ever conducted, Owen Exeter and his team of marine scientists deployed 280 baited underwater camera systems across the Isles of Scilly archipelago, a unique biodiversity hotspot in the northeast Atlantic. The cameras recorded thriving communities of sharks, fish, and crustaceans across habitats ranging from seagrass beds and kelp forests, taking viewers beneath the waves and offering a rare insight into some of the UK’s healthiest and wildest seas. Beyond documenting marine life, the data provide a practical blueprint for designing innovative marine monitoring programmes, helping to ensure conservation efforts are both evidence-based and effective.

Q&A with Dr Owen Exeter

Dr Owen Exeter is a marine conservation researcher at the University of Exeter, specialising in fish and shark ecology in UK waters, West Africa, and the Middle East. His research uses satellite tracking and cutting-edge underwater camera technologies to improve the effectiveness of marine protected areas (MPAs), supporting evidence-based conservation by demonstrating how MPAs can benefit both people and wildlife.

1. Is there any bias caused by the choice of fish bait for use with the BRUVs?

Yes, certain marine species are more attracted to certain baits than others and are therefore more likely to be recorded at the video cameras. This bias is unavoidable. Because we were conscious of this, we elected to use the same bait – oily fish (mackerel) – at every surveying site, for consistency. This meant we were still able to make valid comparisons between sites, which was essential to the project’s goals.

2. What was your process for converting all the video footage into useful data?

People often ask if I used artificial intelligence for this – but I did not. I did it all manually! That’s partly because I thought it would be enjoyable, and partly because it would have been very difficult and time-consuming to train an AI model to do the conversion of video footage to data, particularly the species recognition element. Instead, I used a specialist software called Event Measure (from SeaGIS) specifically designed for the task. I manually watched through all the footage and, using the software, recorded the species present and counted the individuals. For the counts I used a technique called MaxN. For this you record the highest number of individuals present in a given frame. This is a conservative measure of abundance but it ensures you don’t ‘double-count’ individuals, which is very easy to do with underwater footage of schools of fish!

3. Have you investigated recording audio as well as video? Might there be any interesting insights to be gained from analysing the underwater soundscape?

Yes, actually! As a side project of my PhD we set-up cheap acoustic recorders called ‘HydroMoths’ alongside the GoPros to record sound as well as video. The main thing we were interested in investigating was noise pollution. The Isles of Scilly has a lot of boat traffic, especially in summer, and I speculated that this may have an adverse effect on marine fauna. Sadly, in the end, we ended up abandoning this arm of the research as we didn’t really have enough data to draw any interesting conclusions. When it comes to noise pollution some marine species seem to ‘habituate’ to noise. This really complicates things when it comes to assessing whether noise pollution has an impact or not. It would still definitely be possible to investigate this, but you’d need a lot more data. A whole PhD could be dedicated this research topic!

4. Over what time period was data collected?

The fieldwork for this project was carried out over two consecutive summers (starting in late spring and ending in early autumn). In an ideal world it would’ve been nice to survey during the winter too, but the Isles of Scilly are famously exposed and stormy during the winter, so getting BRUVs in the water (a) wouldn’t have been safe and (b) wouldn’t have gathered any useful footage due to turbulence. Even during the summer there were often days when conditions were too choppy and windy to be worth putting out the cameras. Fortunately, when conditions do clear up, the sea around the Isles of Scilly has some of the clearest water in Britain (because there’s no river inflow), so the footage can be excellent quality! To account for the fact that BRUVs were deployed in different locations on different days (and months) we included in our statistical model a control for year, and seasonality using temperature. Interestingly, we found that seasonality had minimal effect on the diversity or abundance of marine species detected. This is likely due to the Isles of Scilly having very stable sea temperatures throughout the year (due to the influence of pelagic water input), with sea surface temperatures only fluctuating a few degrees throughout our study period. Each BRUV is underwater for about 70-minutes and records footage for an hour, which is standardised. An hour may seem like surprisingly little time to record for, but research from scientists in Wales found that actually only around 45 minutes is needed in the UK for a BRUV to detect the majority of large marine species present in an area. We rounded up to be safe.

1. What would be your key recommendations to ensure Marine Protected Areas actually serve to protect the marine biodiversity within them?

Ultimately the protection of Marine Protected Areas (MPAs) is driven from the top level by central government policymakers. In order for MPAs to actually work, there has be a motivation at this level. In the UK there has been at least some progress in this regard. For example, last year there was a big government consultation about a number of MPAs in England focused on ensuring ongoing protection. Generally, however, progress has been slow. On the flip side, there are also things we can do as local managers, stakeholders and citizen scientists. My key recommendation here is to build up an evidence base for the sites you are working to protect – show how special and interesting they are. Then when it comes to consultation or management plans down the line, the evidence base is already there to show policymakers why the sites are worth protecting. Decision-making works top-down, but evidence-building and pressure-applying works bottom-up.

Literature References

  1. Exeter et al. (2025) ‘Application of spatially robust stereo-BRUV sampling for quantifying fish assemblages in UK marine protected areas’: https://esajournals.onlinelibrary.wiley.com/doi/10.1002/eap.70104 
  2. Hawkes et al. (2020) ‘Autonomous underwater videography and tracking of basking sharks’: https://link.springer.com/article/10.1186/s40317-020-00216-w
  3. Rudd et al. (2021) ‘Basking shark sub-surface behaviour revealed by animal-towed cameras’: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0253388
  4. Grorud-Colvert et al. (2021) ‘The MPA Guide: A framework to achieve global goals for the ocean’: https://www.science.org/doi/10.1126/science.abf0861

Further Info

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Published by Joss Carr

Junior Naturalist at Biological Recording Company.

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