Application of the Wildlife Tracker to Conservation Efforts
Whale Shark Tags Appear on Land
As I’ve mentioned in past blogs, Wildlife Tracker is a handy platform that allows scientists to visualise the tracks of marine animals in real-time telemetry data feed. It displays where the tagged individuals are located and overlay environmental variables that might be influencing their movements and understand what anthropogenic impacts might be affecting them.
Find the last story here:
Last year, the Galapagos Whale Shark Project began using the Wildlife Tracker platform to follow the movements of eight whale sharks tagged in August and September of 2018. This included seven adult females (total lengths ranging between 10–13m), which are the norm in the Galapagos Archipelago, where 99% of sightings are adult female whale sharks rarely sighted elsewhere in the world. However, this also included a young female whale shark (total length=5m), a demographic rarely sighted in the archipelago, providing us with the opportunity to compare her movements with her adult counterparts.
Initially, the animal’s movements seemed to be going well. We could see on the wildlife tracker platform how these animals were heading out of the Galapagos Marine Reserve’s (GMR) boundaries and entering the high seas and far from protection. The adult females seemed to follow similar movement patterns, heading from the Galapagos, towards mainland Ecuador and Perú; the most likely movement pattern as reported in past years. Meanwhile, the juvenile, named Sky, took a southbound route. All seemed normal until about two months after the first tagging expedition of 2021.
Wildlife Tracker has implemented an alarm system to indicate when the species being tracked moved in and out of different boundaries. To test it we had to set up an alarm when the sharks moved in and out of the GMR and we had set a water/land boundary. The GMR boundary alarm went off almost immediately, as was expected, highlighting the low residency of the tagged whale sharks in the Galapagos. However, we never expected the water/land boundary to go off. Yet on the 19th of October, one of the whale shark tags began reporting on land, setting off the alarm! It was of an 11-meter shark tagged at the end of August of 2022. (Image 1)
When looking in detail at her tag movements, we noticed several reports of her tag on land in the fishermen’s town of Jaramijó, Manabí, Ecuador. We also noticed a change of behaviour on the 10th of October. Up until then, the whale shark was giving constant transmissions as she was a shallow swimmer, yet on the 10th of October at 6:50 AM local time, her dive profile changed. Until that date, the whale shark was undertaking frequent shallow dives between 0–300m, with most of her dives up to 20m. On that morning her satellite tag transmission quality improved and the tag showed no more dives. The track marked by the tag also changed abruptly in direction and nine days later the tag appeared on land.
Although we cannot say for certain what happened with the whale shark involved, we can say for sure that there was a vessel and shark encounter since these satellite tags do not float. The tag somehow ended up in the hands of humans and was taken to land, with or without the shark.
The story does not end here. During the next months, the water/land alarm went off twice again. Two more of our satellite tags from the adult whale sharks tagged in 2021 appeared on land. The next one set off the alarm on the 1st of November of 2021 and the third one set off an alarm on the 24th of January, 2022 appearing in fishermen's ports of mainland Ecuador (Image 2) and Perú (Image 3), respectively. The stories are similar to the first whale shark’s story. The tags’ transmissions during the reports at sea made a sudden change of direction, stopped showing any diving data, and then reported on land a few days later. Find a visual overview in the next images.
The alarm system from the Wildlife Tracker (Image 4) allowed us to immediately realise what was going on as soon as it happened we received a notification through the Telegram App, and thanks to that we have managed to contact people in these areas and recover two of the three tags.
Both fishermen that returned these tags mention that they never encountered the whale sharks, rather than the sharks must have been entangled with their nets and that the tags remained caught after the whale sharks freed themselves.
“After a short but amazing interaction when we tag the sharks, we watch them disappear into the blue, hopping for the best for them, hopping against all odds they survive… Only to find out a few months later that their tags have ended up on land without us truly knowing what happened to those sharks. It is heartbreaking.”
We hope that these whale sharks continue to swim in the ocean to this day, however, these events highlight the high level of risk of encounters with vessels and intense fishing pressure that whale sharks face. A ~40% encounter rate is preposterous. Whale sharks falling prey to fisheries as bycatch is one of the main threats causing the global whale shark population to decline.
In the past, many whale shark tags have stopped transmitting in this same area off the shelf break of Peru and Ecuador in areas of high intense fishing pressure and after this year we believe many may have been due to encounters with humans.
The main reference to understand the encounters of whale sharks and fisheries is the last location of their tags in the open ocean. Then, to overlay with its monthly fishing effort (In hours at 0.1°) from Global Fishing Watch (On Image 5). Clearly, we can see how the concentration of hours in the fishing effort is near the last locations of whale sharks in the open ocean.
The Galapagos Whale Shark Project is working with Wildlife Tracker to monitor fishing pressure in the areas where whale sharks are moving through and determine the hotspots of possible encounters. With this information, we can present data to policymakers and develop better management strategies to mitigate the impact of fisheries on whale sharks in our EEZs.
We dare to hope that with tools such as the Wildlife Tracker platform we will be able to lessen human impacts and make the ocean a safer place for marine species to thrive.
