Since we began studying the flora and fauna of Curieuse Island in 2007, the expedition has been continuously evolving. Originally set up to monitor the health of the coral reefs around Curieuse and Praslin Islands, it was quickly realised that Curieuse Island and the Curieuse Marine National Park are very special places in their own right. Not least because it is one of only two places in the world where the spectacular Coco de Mer palm grows, and it is the only place in the world where Coco de Mer and giant tortoises coexist in the wild.
Over the course of its existence the expedition has studied many of the island’s endemic and endangered species, with the current range of study subjects including Hawksbill and Green turtles, Sicklefin lemon sharks, Aldabra giant tortoises, mangroves and near shore fish, shoreline stability has been continuously monitored, and invasive rats are now being removed to allow recovery of native species.
The past three months have been an exciting time for the Island Conservation Expedition. We have continued with our annual Aldabra giant tortoise census in order to locate as many free ranging animals as possible. Our target is to find 90% of known individuals and we now only need to find another three to reach this objective.
The tortoise census will be concluded very shortly to make time for the arrival of Hawksbill turtle nesting season and Lemon shark pupping season. This is always the busiest time of year on Curieuse, with daily monitoring of the main turtle nesting beaches. The first nests of the season have now been laid so we will be putting in much effort in the coming months to find and mark as many nests as we can, and attach ID tags to as many nesting females as possible.
The Lemon shark study has been extremely interesting during the low season. We have still been catching Lemon sharks regularly, however we have also been catching a number of other shark species, with some previously not known from the study area. Several pups of Blacktip reef shark (Carcharhinus melanopterus) and Oceanic blacktip (Carcharhinus limbatus) have been captured and tagged, and one Scalloped hammerhead (Sphyrna lewini) pup was also caught. This was the most interesting discovery, and it was also recaptured later, giving us some valuable growth data and confirming it is doing very well in the nursery.
Another exciting development has been the inception of a Lemon shark tracking study. With generous funding from the Seychelles Climate Conservation Adaptation Trust (SeyCCAT) we have been able to purchase 12 acoustic receivers and 25 transmitters. We have done extensive testing to determine receiver detection range prior to the arrival of this year’s pups, at which point we will begin surgically implanting transmitters to follow the pups and vastly increase our knowledge of their movements. This will also help to assess the effectiveness of the national park in their protection.
Another recent addition to the range of projects with Curieuse is an experimental eradication of invasive rats in an area of coastal forest near the base. Rats were accidentally introduced to Curieuse by the original colonists of the Seychelles, and since then they have decimated the populations of many native species. Most notably there are no nesting seabird colonies on Curieuse while close by rat free islands have extensive colonies, and many other endemic species such as lizards have also been negatively impacted. The project has now humanely removed over 550 Black rats (Rattus rattus) from a two hectare area of sensitive coastal forest habitat, and we are now beginning to see encouraging signs of ecosystem recovery.
The Baited Remote Underwater Video (BRUV) study has captured 36 hours of video footage of carnivorous and scavenging fish species in shallow and deep habitats off the poorly studied north coast of Curieuse. Review of the footage has just been completed, and data analysis will begin shortly, however one notable new discovery this season was a Snaggletooth shark (Hemipristis elongata). We await the results of the analysis to see the comparison in these fish detections with previous seasons.
The annual mangrove survey was also conducted in August, with eight permanent 10m x 10m quadrats being surveyed to assess the trends in mangrove species abundance, diversity and recruitment. The data is currently being analysed and we will shortly find out what changes, if any, have occurred since August last year.
It has been a very busy three months for the Seychelles Curieuse Island Conservation Expedition. In addition to our long running research projects which continue to produce valuable data on the health of the national park, we have added some exciting new studies which will not only expand our knowledge of the species on and around the island, we are now making significant progress in returning some of the habitats to a more natural state.
We would like to thank you for all your support, it's greatly appreciated!
Seychelles Curieuse Island