On 29th Feb. 2004, the second of what is now an annual expedition to explore a South Australian island group, began with great excitement at the Althorpes island group. The last trip was to the Nuyts group and next year it will be the Investigator/Sir Joseph Banks group.
The Althorpes are approximately 8 km SW of Innes National Park and can easily be seen from the mainland of the Yorke Peninsula. Althorpe Island has a long European history with its lighthouse keepers. The lighthouse was built in the late 1800’s and there are three lightkeeper cottages on the island, one for the family of each lightkeeper. In fact one of the main council members in the group actually grew up on the island because his father was a lightkeeper, then he became a lightkeeper and also worked on the island.
There are many wrecks around the island that are well documented. Althorpe Island Conservation Park has a very active Friends group who are very keen to have experts come and assess the island for conservation and heritage purposes. The group has undertaken huge vegetation mapping surveys of the island and has had grants for eradication of boxthorn and feral cats.
Past experts to visit the island and write up reports include Graham Medlin, from the SA Museum, who examined the sub-fossils, and Ben Pavy a native vegetation expert from the Yorke Peninsula. I have also been to the island twice previously: once to assist in boxthorn eradication and once to undertake an amateur study of the intertidal organisms. This trip, unlike the Nuyts, was solely marine research. The trip happened in two parts because there were so many interested people. Some stayed on the island, while most were on the RV Ngerin, the SARDI Aquatic Sciences research vessel. I only attended during the second ‘batch’ of the trip, but some like Scoresby Shepherd (MLSSA’s Patron) and Anthony Cheshire, Director of SARDI Aquatic Sciences, stayed the whole trip. Scoresby was so keen he even stayed on a few extra days on the island.
The Ngerin was invaluable for transporting the large number of people and all their gear. However, at the other end the luxury was over. The famous ‘flying fox’, which had been used for decades for transporting large heavy goods to the top of the 90m tall island, had been decommissioned! We had to walk everything to the top of the island ourselves in stifling heat. It is a long and arduous path to the top of the island, where the cottages are so no one wanted to do more than one or two trips a day.
This trip included:
- Graham Edgar, University of Tasmania and author of ‘Australian Marine Life’ and ‘Australian Marine Habitats’
- Thierry Laperousaz, SA Museum, Collection Manager, Marine Invertebrates (non-Mollusca)
- James Brooks, Reef Watch Project Officer
- Brad Page, University of ?
- Sue Gibbs,
- Kirsten Benkendorff, Flinders University, Lecturer in Marine Biology
- Dave ??, Melbourne Museum, Pycnogonid expert
- Neville ??
- Sue Murray-Jones, Coast & Marine Branch, DEH
- Tim ??, District Ranger, Yorke/Mid North Region
- Caroline Paterson, Senior Ranger, Innes National Park
The media came and produced a small news report on two channels. They stated that the trip included researchers from 4 states, 4 universities and 3 museums.
I was lucky enough to accompany Dr Kirsten Benkendorff, as a volunteer on my third trip to the island. Kirsten works on a number of different research topics associated with the biological and chemical ecology of intertidal molluscs (and we should get her to do a talk!). On this trip she was undertaking intertidal species surveys to compare the island with the mainland. My learning curve was pretty steep and I saw some mollusc eggs that I had not seen before and a pair of sea hares (Aplysia parvula) that I had only previously seen in Victoria.
Kirsten does an accumulated time series. She times the survey for one hour, but divided up into 6 sections of ten minutes each. She carries around a clipboard with about 6 sheets of species lists (including some common intertidal Echinoderms) on which she writes down in which time period she finds a species. For example, in the first ten minutes (period 1) she will usually find many species, in the second time period as they become harder to find, she should find a few less (each species only gets marked off once), by the time she gets to time period 6, the accumulation of species being found should level off and she often does not find any new species by this time. On rare occasions if she is still finding significant numbers of new species, then she will continue the survey into another ten-minute time period. At the very first survey site on the island, she had to continue the survey into another two time periods! Of all the surveys she did, the first site produced the highest number of species. The results of all the research from this trip will be published in a special edition of the Transactions of the Royal Society of South Australia.
Groups of organisms covered by the various researchers included: algae, molluscs, pycnogonids, fish, dolphins and seabirds. The muttonbird research took place on the island, at night, and was a noisy and dirty affair. The birds migrate to and from the island every year, to breed there during the Australian summer. At this time of year the birds have fairly large chicks that the parents take turns to feed at night, while they hunt during the day. Brad Page was looking at their feeding habits but to do this had to flush the adult birds stomachs to make them regurgitate. He had at least 4-6 volunteers helping him every night.
Muttonbirds dig burrows for their chicks, so the work involved lying down on the ground and putting your arm down a burrow to see who is home. Fortunately there are no snakes on the island! If you find an adult in the burrow, the technique is to get it to bite you then grab hold of its beak and pull. All birds were weighed, measured and flushed. This work continued every night from about 9 or 10 pm to about 1 or 2 am. There were lots of tired volunteers on the island!
It is hard work getting around the island. The cliffs are steep and Kirsten and I were like mountain goats for a couple of days on some very precarious paths. It wore us out a lot, so 2 surveys a day around low tide was plenty of work, followed, on the 2nd day by some snorkelling to relieve the high temperatures. The granite rocks at the base of the island were so hot that when sea spray hit them, steam rose off! A cool dip was a great relief. It was a lovely reef environment around the granite rock area, with profuse amounts of algae and some large fish, including the largest zebra fish I think I’ve ever seen! It reminded me how great the SA marine environment is.
One interesting thing we noticed, which Scoresby later confirmed, is that the limpet, Cellana solida, is on average very large on the island, compared with mainland specimens. Scoresby has noticed that many islands have much larger limpets than mainland populations, but nobody knows why. On our last day, the ex-lightkeeper, John, took Kirsten, myself and two others out in a zodiac to see the NE and Eastern side of the island. On my previous trip, John actually rowed me around this same area and I took loads of pictures of the different intertidal zones with some lush algal communities. It is a lovely trip to do in a boat, as you get to see many otherwise inaccessible areas including getting close to Chain Island, where a New Zealand fur seal colony hauls out. On this trip there were not many animals around, perhaps less than fifty, compared with my previous trip when there must have been over a hundred. The seals had been popping up around the island to investigate all these people and kept a close eye on us. We had quite a few close encounters.
Kirsten and I stayed on in Innes National Park, with an honours student of hers, to complete a number of surveys with which to compare the island. I look forward to the results of Kirsten’s hard work. This was yet another fabulous trip and one that I believe was worthwhile for everyone involved. Keep an eye out for details of next year’s island research trip!