Introduction: Why Seals and Why This Project?

Seals are one of the UK’s most iconic marine mammals. Here in Cornwall, we are especially fortunate to have regular sightings of grey seals and harbour seals, globally rare species found only in the North Atlantic. In fact, the UK is home to around a third of the entire world’s grey seal population, making our local waters vitally important for their survival.

Seals face many challenges. Human activity at sea is increasing rapidly, from offshore wind farms and aquaculture to shipping, fishing, and communications infrastructure. These activities create new pressures on marine ecosystems. In the southwest, this issue is particularly significant, as the Celtic Sea is both a hotspot for seals and a focal point for the UK’s renewable energy development.

To protect seals effectively, we need to better understand how they use their environment. Traditional monitoring methods, such as tagging, can be invasive, stressful for the animals, and limited in the amount of data they provide. That’s why we’re working on Seal Spy: a new audio-visual monitoring system that uses cameras, hydrophones (underwater microphones), and artificial intelligence to track seal presence, behaviour, and vocalisations without disturbing them.

Seal Spy

Do seals vocalise underwater?

Yes - but surprisingly little is known about when, how often, and why. By recording and analysing their underwater sounds, we can start to answer questions about seal communication, social interactions, and how they respond to environmental changes.

How can you help?

We’re training a neural network (a type of machine learning model) to automatically detect seal calls. To do this, we need thousands of examples of seal vocalisations. Our hydrophones have already collected over 1,000 hours of recordings, but we need help tagging the calls, identifying their position on spectrograms (visual representations of sound).

Each tagged call helps us improve the accuracy of our system. With enough data, Seal Spy will become a powerful, non-invasive tool for conservation and marine planning, providing the evidence needed to protect seals while balancing the demands of sustainable development.

By joining this project, you’ll be directly contributing to:

• Protecting a globally rare species.

• Developing cutting-edge, ethical monitoring methods.

• Supporting better decision-making for the future of our oceans.

This is where you come in, helping us spot and tag seal calls. Don’t worry, we’ll guide you through everything step by step and even let you test your skills with practice images and sounds.

Volunteer Training: How to Tag Seal Calls

1. Understanding Spectrograms

• A spectrogram shows time (left to right), frequency (low to high, bottom to top), and loudness (brightness/colour).

• Seal calls often stand out as distinctive, arching or swooping patterns. They may look different depending on the seal, background noise, and environment.

• Sometimes, background sounds (waves, boats, fish) can make it tricky, that’s why your help is so valuable!

5 distinct seal call spectograms annoted on Rave Lite software

2. What You’ll Be Doing

To get a good understanding of how we spot and tag calls, it’s best to go through some training and practice exercises. This will give you a feel for the process and help build your confidence.

Our project uses spectrograms, images that show sound. Each spectrogram comes from hydrophone recordings of the ocean, where seals (and other animals) make sounds underwater.

Your task is to:

1. Watch and listen to short spectrogram clips.

2. Try to spot the seal call(s) (they often appear as curved or streak-like shapes).

3. Keep a mental note of where you think they are.

4. Check your answer in the next image, which highlights the correct call(s).

This training will help you practice before you begin real tagging.

3. Step 1: Practice with Sound (PowerPoint Download)

We’ve created a downloadable PowerPoint presentation for the training section.

Download the Training PowerPoint

Here’s how it works:

1. Open the file and go into presentation mode (if you don't, you'll risk seeing the boxes on screen before guessing).

2. Each slide will show you a spectrogram image (with audio if you click the speaker icon).

3. First, look and listen carefully to try spotting the seal call(s).

4. When you’re ready, click once - a bounding box will appear around the correct call(s).

5. Click again to move on to the next example.

Repeat through all the slides to practice your spotting skills.

Note: Please make sure your sound is turned up. Because these examples are screen recordings, the background noise comes through more strongly than it does in the original files. This can make the seal calls harder to detect, but it’s great practice for training your ear and eye. In the actual tagging software (Raven Lite, more on this later), the background noise is much softer and the calls appear much clearer. Also, in this training, the calls may sometimes appear slightly out of sync with the moving playback bar, don’t worry, this won’t be an issue when tagging for real.

4. Step 2: Practice Without Sound (Continuation of PowerPoint).

Now that you’ve trained your ear and eye, let’s see if you can spot calls using the spectrogram alone. Following on from the video clips, you will be moving through images only, without audio. The same rules apply, please try and spot the calls and make a mental note of where they are, the answers will appear in the following slide.

5. You’re Ready!

Once you’ve completed the practice, you’ll be ready to join the main tagging effort. Every clip you tag brings us closer to building a large library of calls, the foundation of a powerful conservation tool to help protect seals.

Next Steps

If you feel confident after completing the training, please contact us at harrison.smith@celticseapower.co.uk and we will provide you with access to our 2-hour audio (.wav) files***.

On average, each 2-hour file contains between 10 and 100 seal calls, although this can vary depending on factors such as time of day and tide. Our recordings come from both the Cornish Seal Sanctuary in Gweek and in-situ deployments at sea along the north coast of Cornwall.

Once completed, you will receive a certificate of work jointly issued by Celtic Sea Power and the Cornwall Seal Research Trust. We have 2 levels, basic and star (latter for those who do over 3 files). If you’d like to continue contributing beyond your first file, we’d be delighted to arrange further datasets for you to tag. Each of our files is a minimum of 2 hours.

On this page, you’ll also find a link to our step-by-step guide for using and tagging calls in Raven Lite, a free software package available to download online.

If you require any additional assistance at any point, please don’t hesitate to get in touch, we’ll be happy to support you.

***Disclaimer

All data, materials, and recordings associated with the Seal Spy project are the property of Celtic Sea Power Ltd. They are provided solely for research, educational, and conservation purposes within the scope of the Seal Spy volunteering programme.

Volunteers are granted access to these materials on a temporary, non-commercial basis and must not copy, distribute, publish, or use the data for any other purpose without prior written consent from Celtic Sea Power Ltd.

While every effort has been made to ensure data accuracy, Celtic Sea Power Ltd makes no warranty, expressed or implied, regarding completeness, reliability, or suitability for other uses. Participation in this project is voluntary, and Celtic Sea Power Ltd shall not be held liable for any loss or damage arising from use or interpretation of the data or materials provided.

© Celtic Sea Power Ltd. All rights reserved.