Whale sharks are the largest fish in the ocean and an awe-inspiring sight to behold, yet very little is known about them. Listed as Endangered on the IUCN Red List of Threatened Species, gaining a good understanding of some of the basic life history questions about this animal is now essential.
The Galapagos Islands are one of several locations that whale sharks are known to visit at certain times of year, typically visiting the northern islands of Wolf and Darwin between June and December. Unlike aggregations in the Indian Ocean, which are largely made up of small immature males, the majority of sharks sighted in the Galapagos Marine Reserve (GMR) are large mature females, a high proportion of which (over 90%) appear to be pregnant. Given the lack of knowledge in the breeding ecology of whale sharks and the apparent frequency that pregnant females are seen in the GMR, an exciting research opportunity exists.
What we have learned so far
In 2011 the Galapagos Whale Shark Project research team satellite started to tag whale sharks, the majority of which were pregnant females. The type of tag used recorded the position of the shark each time the tag broke the water’s surface, allowing for their horizontal migration to be tracked.
Sharks tagged at the beginning of the season appeared to move in a westerly direction for hundreds of kilometres, then returned east later in the season, often passing close to Darwin Island again, before continuing on towards the continental shelf. Sharks tagged later in the season moved to the continental shelf and remained along the shelf break for extended periods. Despite none of the tagged sharks remaining within the GMR for more than a few days, their predictable annual appearance suggests that the Galapagos is still an important location within their migratory pattern and further research into why pregnant females are using the area could be highly insightful.
Field Season reports
GCT have funded trips by the team since 2014. Since 2011, over 60 whale sharks have been tagged with at least one tag (some were tagged with two different types of tags), and over 170 individual whale sharks have been identified using photo identification methods. The tags have allowed the team to successfully tracked shark migration routes from the Galapagos Islands to the coast of mainland Ecuador and Northern Peru. In addition, miniPAT tags allow us to increase our about the sharks’ diving behaviour, and camera tags are providing new insights into the interactions of whale sharks with other marine life.
The whale shark tracks generated by this project have already bought about real conservation and management outcomes. In 2016, the Galapagos National Park requested the tracks as part of the on-going process to re-zone the Galapagos Marine Reserve to protect the megafauna found around Darwin and Wolf islands. The track data recorded was key to the successful closure of the waters surrounding Darwin and Wolf islands, which were designated as a shark sanctuary or “Shark Reserve” and a ban was implemented to stop all fishing activities in this zone.
To view the field reports from the trip, select one of the options below:
Outreach and education is also extremely important for the Galapagos Whale Shark Project. The team visit schools in Galapagos and Peru, and in 2016 reached over 1000 children. In 2016, they also gave presentations to communities in Galapagos, Navy personnel on mainland Ecuador and artisanal fishermen in Peru.
The overall aims of the Galapagos Whale Shark Project are clear: To improve our understanding of the GMR’s significance with respect to whale shark migratory pattern; to increase our knowledge of whale shark migration patterns; and to educate local authorities and communities so they can devise effective management strategies for whale sharks in the GMR. With the tracks showing connectivity with populations seen off the coast of Peru, it is also important to engage with stakeholders there.
This will be achieved by continuing to satellite tag individual sharks across multiple seasons, photo-identifying all whale sharks that are encountered, taking tissue samples for population genetic research, confirming pregnancy in at least one female shark, and attaching “Daily Diary” tags to individuals to assess their use of the magnetic field. In addition, aerial surveys will be taken using drones.
Wildlife tourism is a booming industry around the world, and whale sharks are no exception. Conserving these gentle giants is key for the continuing success of marine-based tourism in Galapagos, which benefits both animals and local communities. With your support, we can continue to fund this crucial project.