Sea Turtle Tracking

Since the start of the VIZ - Sydney Diving Visibility Reports in 2019 we have been collecting reports of sightings of sea turtles with the goal of understanding their presence patterns through time series. Surely we are no scientists, we do it for fun, but we like to think we are contributing to the local knowledge, especially when filling knowledge gaps like knowing how many different sea turtles are spotted around Sydney and their presence pattern.

Sea Turtles are found within a huge range of latitudes, from Japan to our coast all the way down to Narooma. For many countries, seeing a sea turtle in the wild is synonymous of extensive travelling to tropical destinations, but thanks to the East Australian Current we find them right at our doorstep, one of the last stops in their North-South journey.

These are the different individuals that we have been able to identify by collecting and analyzing all the pictures posted on VIZ. By comparing the patterns on the skin and the shell we can link a sighting (picture) to a sea turtle in our database or create a new record if there is no match. The goal is to have a sense of how many different sea turtles are spotted in Sydney and how long they stay, which is an information that has never been available before. It's a significant investment of time, but it allows to preserve and share the information contained in the visibility reports, that otherwise would sink into oblivion in the Facebook feed.
We also track other 9 species, not individuals but
observed quantity, to know more have a look at the FAQ.

The image below is a preview, you can't actually read the fine text, but you can download the high resolution PDF here

Interesting observations by looking at the data (as of 6/2022)

  • Most of the turtles have been identified in the period 6/19-6/22, plus some coming from pictures retrospectively collected from 2015 to 2019.

  • 85% of them are Green Turtles (Endangered) and 15% Hawksbill (Critically Endangered).

  • A number of sea turtles stayed in one site for weeks or months before disappearing and then reappearing months after in the very same place.

  • No turtle has ever been found in more than 1 of the 12 sites monitored: either they don't move from their elected site or they leave the region, and when they return they pick always the same site.

  • July has been the month with more individuals spotted (see graph above), which is interesting considering that the natural drop of divers during the cold season would have suggested otherwise.

The turtle presence across time (green) and the time spent in rehabilitation (yellow). The table spans to before the start of the project (6/2019) thanks to additional pictures that we have been collecting retrospectively

A graphic produced by VIZ to inform swimmers and divers