As apex predators, sharks directly and indirectly affect all levels of the food web, maintaining a healthy ocean environment for many species. Unfortunately, today many shark populations are on the decline. The loss of these amazing animals could prove devastating to our oceans and our planet.
Twenty years ago, French Polynesia created the largest shark (and marine mammal) sanctuary in the world, encompassing the whole of the five million square kilometers of the country’s exclusive economic zone (EEZ). Polynesians have always understood the critical ecological role of sharks and they occupy an important place in the culture as totems and messengers.
Scientists from the University of Washington led by Dr. Aaron Wirsing are continuing their work on sharks in Tetiaroa. They recently began to deploy acoustic receivers inside the lagoon that are capable of tracking tagged Blacktip Reef Sharks and Sicklefin Lemon Sharks for years to come.
The team is working to protect sharks by better understanding their behavior and movement patterns. Their long-term study tracking sharks aims to provide a baseline of movement information that they can use to assess the impacts of future changes like warming waters, ocean acidification, coastal development, differing fisheries management scenarios, and more.
In 2020, the team contributed and published a first-of-its-kind study in Nature reporting the conservation status of reef shark populations worldwide. The results were startling; reefs sharks have become rare at numerous locations that used to be prime habitats, and in some cases, sharks may be absent altogether.
In addition to gathering baseline data on shark behavior, the team is hoping the data collected for this project will be able to answer a number of ecological questions. Including:
- Are there any 'hotspots' of shark activity?
- Do (and if so how) juveniles and adults use the lagoon differently?
- If sharks leave the lagoon, do they return in subsequent years?
- How long do juvenile sharks stay inside Tetiaroa's lagoon before potentially migrating to the nearby islands of Tahiti or Moorea?
They are also hoping to add supplemental receivers to expand their spatial coverage outside the lagoon in upcoming years, as well as to begin tagging efforts for other shark species (e.g., Grey Reef Sharks, Whitetip Reef Sharks). Finally, the receivers being deployed this year will be utilized by the other research projects taking place in Tetiaroa and could allow for tracking the movements of a variety of teleosts and marine reptiles.