Written by Petr Slavík

Cover photo: aerial image of one of the humpback whales encountered this season. By Petr Slavík


Throughout their lives, cetaceans are required to make significant energy investments into several vital behaviours ranging from mating and reproduction to foraging and even migration in certain species. Body condition, a measurement of the animal’s fitness based on the balance between its energetic intake and investment, plays an essential role in these vital behaviours. Simply put, a healthy body equals not just a healthy mind, but also successful reproduction and, ultimately, an effective life supporting the health of the animal’s population and its overall existence. This means that any compromise to the individual’s body condition may have a negative impact on the individual’s or their offspring’s fitness and survival. If taking place over many individuals simultaneously, these impacts can compromise the population size and even its future.

Aerial image of a minke whale encountered during our field season. By Flordespina Dodds


Today, a wide array of human-induced stressors may impact the body condition and, ultimately, the lives of the world’s cetaceans. Climate-related impacts, pollution, underwater noise, ship strikes, overfishing, or entanglement and fisheries bycatch are all examples of human-induced stressors that can be fatal to cetaceans or have a significant impact on their welfare and reproduction if not appropriately regulated or mitigated.

Fisheries entanglement and bycatch are especially concerning issues regarding the potential impact on cetacean body condition. Long-line fisheries using baited hooks, for example, can lead to injuries sustained by the cetacean’s inability to dislodge itself from the hook, often leading to entanglement in the fishing line or breaking free with the hook stuck on its body. Fishing gillnets, on the other hand, can drown the accidentally caught cetacean or cause significant injuries, such as cuts, abrasions, bruises or broken bones. Even without a lethal impact or causing injuries, entanglement in fishing gear can also cause significant stress to the animal, which can ultimately impact its health and fertility in the long-term.  Therefore, unsurprisingly, it is of great importance to study, understand and, above all, prevent these long-term impacts of entanglement on the individual body condition of cetaceans.

Aerial image of a humpback whale with multiple scars. By Jessica Ward  


This year, Whale Wise has decided to try to fill some of the gaps in our understanding of the possible link between fisheries entanglement and the body condition of individual humpback whales migrating to Icelandic waters. To do this, we have commenced a new project called Scars from above, which aims to look at entanglement scarring on humpback whales and relate its extent to individual body condition. 

Since August this year, we have been out in the field collecting data for the project, using humpback aerial images captured by unoccupied aerial vehicles (aka UAVs or aerial drones). For this, we have based our field team in a small Icelandic village called Drangsnes, located on the northeast coast of the fjord Steingrímsfjörður. This fjord consists of several deeper, nutrient-rich areas used as feeding grounds by seasonally returning humpback whales. Large volumes of whales aggregate in the fjord every summer and fall, which allows us to collect aerial footage and assess the body condition of tens of individuals. On top of that, as some whales are expected to return to this area repeatedly, this approach will also allow us to track changes in the body condition of individual whales over time, eventually giving us the opportunity to possibly understand the potential impact of entanglement over several years of the whales’ lives.

Release of our drone Oscar. By Rebecca Douglas 
Sea birds enjoying their supper – a sign that the waters of Steingrímsfjörðurr, our study location, are rich in nutrients. By Rebbeca Douglas 


Most importantly, you need a team of dedicated and skilled researchers and, of course, a reliable drone. This year, we were fortunate to raise funds to purchase DJI’s new Mavic 3 drone, which allows us to drone across significant distances for prolonged periods – a pivotal facet of aerial imagery. It is incredible how much public support we have received over the last several months. Not only does it allow us to do this project, but it also fills us with an immense sense of hope for our future work, and, above all, the future of cetaceans. For this, we are forever grateful! 

A humpback whale measured using aerial imagery. By Petr Slavík
Oscar – our aerial drone equipped with LiDAR. By Rebecca Douglas 

However, despite its excellent camera and other technological advances, the drone is just a part of the whole project’s puzzle. To assess the body condition and the biomass of individual cetaceans, we also need a device to measure the length and width of the individual. To do this, we are using a custom-made device called Light Detection and Ranging (aka LiDAR), which you can see attached to the belly of our drone, Oscar, in the picture above. LiDAR projects two laser beams, effectively working as a pair of eyes, onto the back of the cetacean during surfacing, which gives us much-needed information about the flight – particularly the altitude. Additionally, the LiDAR is equipped with a specialized GPS receiver which allows us to log the exact position of the measurement readings. When done with droning, we can then collate the captured video with the altitude measurements, which allows us to measure the biomass of individual whales, and ultimately assess the well-desired body condition.

Alyssa and Flo identifying different humpback whale individuals using aerial imagery. By Rebecca Douglas 


Cetaceans are key ecosystem engineers responsible for the oceanic movement of nutrients essential to other animals, either in the form of their faeces or carcasses. Being apex predators to some species or important prey to others, they also contribute to the stability and health of their ecosystems. Last but not least, cetaceans provide a natural carbon sink, ultimately helping humanity fight climate change and the global impacts associated with it. However, as mentioned earlier, cetaceans are still under the threat of fisheries bycatch and entanglement, which continues to put their future population health into question. To prevent this, robust and transparent management systems for fisheries where bycatch and entanglement still occur are needed more than ever.

A humpback whale fecal matter. By Petr Slavík

By understanding the long-term non-lethal impacts of entanglement on cetacean body condition, we aim to scale up the importance of fisheries management and the protection of areas that are instrumental for the local cetaceans’ health and, subsequently, the underlying ecosystem stability. However, science alone will not get us to the stage of protecting the local whales from entanglement and bycatch. Therefore, we also aim to work with the local community and collectively search for solutions that could reduce the potential local entanglement of cetaceans. Even then, however, our work will be still far from being done. Humpback whales, in particular, are migratory species covering vast distances throughout their lives. This means their body condition can be under threat even outside their feeding grounds here in Iceland. This is why it is so fundamental to raise awareness about the impact of fisheries entanglement and progressively work towards a scheme that will monitor fishing activities even along the whale’s migratory corridors.

Well – challenge accepted! In the meantime, stay tuned for updates about the project and make sure to support our work if you can. Thank you! 😊

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