Manta Project Update - July 2010
Our trip to Lady Elliot Island Tagging and biopsy sampling:
We equipped 3 more mantas with 2 acoustic and 2 satellite tags. One of them, a male named Cousteau, was tagged with both acoustic and satellite tags. This "unlucky” male will provide us with important information on his movement by making the link between his broad-scale movements (via satellite tracking) and finer scale movements at our study sites (via acoustic tag). In addition, the double tagging will allow us to check the accuracy of both technologies used and to compare of the two types of data obtained.
We also collected biopsy samples from four different animals. A hand spear fitted with a biopsy tip was used to get muscle tissue from the animals. These tissue samples will give information on the genetic structure of the animals as well as diet information where fat molecules will be used to investigate the feeding habits of manta rays.
Six listening stations were redeployed around the island providing a great coverage to detect acoustically tagged animals swimming around Lady Elliot (red triangle on photo=listening station positions). This technique gives us precious information on the residency and site fidelity (coming back to the same site several times over a long period of time) of our tagged mantas.
Taking measurements of manta rays:
One of our underwater cameras was equipped with two red lasers, 20 cm apart, projecting two parallel beams of light on the manta body used as a “scale bar”. This technique allows us to estimate the disc length (from the mouth to the pelvic fin) of the animals. Love is in the air Intensive courtship behaviour, where one big female swims closely followed by several males, was seen and filmed at several occasions during our trip. In addition, most big females had mating scars on their left pectoral fins (from the male grabbing the fin during copulation) and always closely followed by mature males. The mantas honoured us with courtship dances where the female starts doing looping motions and the males try to imitate and follow the same movements. During one of the courtship trains, one of the males was even looping in harmony belly to belly with the female for a few seconds. No mating was observed but we are pretty sure it has been happening! These observations are of great importance as it indicates that LEI is probably an important breeding ground for these animals.
Although our first week was fairly odd, with lots of mantas the first few days then no mantas at all for 2 days in a row, the second week was marked by a true manta festival. We photographed up to 12 different mantas in one dive!! On top of that, we had the great chance to swim amongst a big group of mantas feeding for a whole hour, astonishing memories and emotions!
Result from this trip:
We identified over 100 mantas during this trip, including 38 new individuals. A lot of these animals were also seen last year in June. Four of the resighted mantas - Cloud, Etoile, Damia and Chiron - belong to the group of identified travellers that seasonally move between LEI and Nth Stradbroke Isl (counting 26 mantas to date). One young female called Juliane was also seen at LEI, she was last sighted in March 2010 at Byron Bay. We now know that at least 4 mantas have been travelling between LEI and Byron Bay.
We now have 415 manta rays identified to date!! Amongst those 200 were resighted at least once! And there are still more photos to look through!
Volunteer with EarthWatch for Project Manta
Once again we had an exceptional trip with our EarthWatch volunteers who just made our trip efficient and fun! We still have several trips planned at Lady Elliot Island with EarthWatch, so if you are interested in volunteering don't hesitate to contact us or write to firstname.lastname@example.org. Places for these trips are filling up fast so make sure you book ahead. You can also visit the webpage: http://www.earthwatch.org/australia/exped/townsend_research.html
If you want to follow our adventures, share your manta experience(s) or ask us questions you can also visit on our facebook fan page: PROJECT MANTA_ The manta rays of eastern Australia.
The Project Manta team
Lydie Couturier Fabrice Jaine Kathy Townsend Scarla Weeks Anthony Richardson Mike Bennett