Hi again
In between dealing with illegal foreign fishing vessels and asylum seekers we managed to get some more marine research done in November.
Concerningly, our research confirmed that marine turtles are facing some significant challenges. In the Croker Island area the main species is the Green turtle with Flatbacks, Hawksbills, Leatherbacks and Olive Ridleys also showing up in much smaller numbers.
Below, the CDU vessel with Elle, Carol and Garngi ranger Tyson waving for the camera.
Over a couple of days we surveyed 35 kilometres of beach in northern Croker Island for recent turtle nests. There was a similar survey conducted in November 1996. Back then there were 75 nests recorded. In 2024 we only recorded 14 recent nests for the same area. We were expecting to see a decline in the numbers but not to this extent. This is very alarming!
Below, the short video shows us on the east facing beach of Cape Croker. The conditions were hot and humid but very flat.
Drones are being used more and more in wildlife surveys. In the video the drone is being prepared to fly along this beach looking for nests. Most of the drone surveys we did were over foraging areas. The drone is setup to fly a grid patterns. The footage is analysed at a later time. From this footage, turtle numbers and the gender of adult turtles can be recored. This works much better when the sun is low in the sky. When the sun is high in the sky this produces a lot more reflections from the water surface making it much harder to spot the turtles.
While on this beach we came across two dead sharks washed up on the beach with all their fins and tails cut off. Shark fins are a popular Indonesian fishery. The rest of the shark is just discarded.
The CDU vessel silhouetted against the morning sun as we head out on another day of research.
The photo below shows two fresh turtle tracks - a strong indicator of a nest from the previous night. We will take a closer look.
Just nearby a ghost net on the beach. This one did not have any dead marine animals in it however this often is the case. There are no vehicle tracks to this area so we will have to return at a later time in our boat and cut this net into smaller pieces to retrieve.
Finding the turtle egg chamber can be tricky as the female can dig in several places before laying her eggs. Below Sonny pokes a long stick into the sand. Where the egg chamber is located the stick will go into the sand much easier.
When the nest is located the end of the stick is inspected for signs of a punctured egg - like the one Tyson is holding. Green females usually lay around 100 eggs.
A temperature logger is placed on top of the eggs and the hole filled in. Care must be taken not to move the eggs as after two hours the embryo has attached to one side of the egg and if we turn the egg this will cause the embryo to die.
And then we dig in this aluminium cage over the nest. Off the 14 recent nests we found - mentioned earlier, 13 had been predated - mainly by goanna and one by feral pigs. The cage helps to keep these predators out of the nest.
On this cage we placed some casuarina tree leaves to keep the sand a little cooler which will hopefully result in a more even gender ratio of the hatchings.
On another cage we trialed some shade cloth.
Below Tyson dives in and catches a smaller but agile Green turtle.
The rangers regularly try to get me to have a go at diving. I feel it is prudent to leave this to the younger ones.
A couple of the male Garngi rangers were rather surprised at how good Nat is at catching turtles. Elle had a few goes but is still to catch her first.
As you watch the short video below, continue tracking the turtle for as long as you can after it is released. If your eyes are good you should be able to see it right to the end of the video. When we are looking for them, initially we may only see a small shadow in the water many metres away - similar to the very end of this video.
Another angle of the same release. You can see the depth of water here is less than a metre. We need to be very careful not to damage the boat or the outboard motor leg/propeller while operating in shallow water like this.
Below our research team - PhD candidate Nat is in the water with her underwater camera, in the boat L to R - Bryan, Elle, Sonny and Tyson with Dr Carol Palmer taking the photo. A few days after this photo was taken Nat got stung on her leg by a suspected box jellyfish through her stinger suit. It still caused a nasty burn. While we have people in the water we also have to keep a good lookout for crocs and sharks. They usually don't bother us however we can't be too careful.
Back at the ranger base and just before Elle, Carol and Nat were taken to the Croker airport to return home. They will return again next year for another four field trips.
Garngi Rangers decided to give our marine researcher colleagues one of our new rangers shirts each as a thank you.
I hope to produce another post before Christmas with our family news.
Until then, take care.
Comments