By Juliette Hennequin
It’s been almost a week since the SMSG team has left Ascension island now, yet I still haven’t had time to describe all the studies we’d been doing down there. Indeed, the one that I am about to fill you in about is the one that Dion & myself had been assigned too, and is in fact one of the most challenging ones. I will no longer hold your breath, and get on with the facts!
Our task was to collect fish specimens, in order to provide a useful database, which would also be very valuable for the possible future establishment of a fishery. We were focusing mainly on three species during this trip: Squirrel Fish, Rockhind (Grouper) and the Spotted Murray. Each fish we caught would be brought back to the lab where we analysed them, measuring and weighing them, then extracting the otoliths and taking gonad samples. Otoliths are commonly referred to as “earstones” or “fish ear bones.” They are hard, calcium carbonate structures located directly behind the brain of teleost (bony) fish. Otoliths help with balance, orientation, and sound detection-much like the inner ear of mammals. They are not attached to the skull, but “float” beneath the brain inside the soft, transparent inner ear canals. Thin sections of an otolith reveal bands of opaque and translucent material, sort of like the rings on a tree trunk. They are most often used in determining age.
So once or twice everyday, Dion and I would trade our scuba diving equipment for a snorkel and a speargun, and go hunting for fish. Both keen free divers, we enjoyed the break in the daily routine and were eager to go spearfishing whenever we could. But unlike what most fishermen do, the aftermath in the lab proved to be a bit different to the usual filleting, as we grew accustomed to processing all the fish by ourselves. Needless to say after processing about 25 fish for day, the appetite to actually filet them and serve them at the dinner table seems to shrink inexorably. On the other hand, we both learnt a great deal about these 3 fish species, and Dion is know an expert at extracting otholiths!
By Simon Morley,
One of the reasons for digging into the tile fish nest mounds is the hope that we will find either a species new to science or one that has not been found at Ascension Island before. One of our samples was unusual in that, whilst it had the usual pile of maerl balls, these were lying on top of a mound of sand. As we were carefully searching for the last of the critters a snake eel popped its head out of the sand. I was able to quickly grab it and gently ease the foot long eel out of the sand. When it came back to the lab the fin on its back was clearly visible, the small eye indicates that it has poor vision and it was realised that this species not been described from Ascension.
In conversation with Sam Weber, the director of science at the Ascension Island Government Conservation Department, he says that he occasionally sees bits of an eel like this that get washed up on the beach. So fingers crossed we have added a piece of knowledge to the biodiversity of this remote Island.
By Paul Brewin
The new species and new records keep pouring in as the SMSG and AIMS team is on its 10th day of our 2015 Ascension Island diving expedition. As with previous years, specialists Jude Brown and Peter Wirtz helped identify crustaceans, nudibranchs, flatworms, anemones, and corals that are either new records for Ascension, or new species to science.
This year the team has focused on those places that have been historically overlooked, such as the labyrinth of spaces in tile fish piles (see previous blog entry), cryptic species living inside rhodoliths (balls of calcareous algae that contain small spaces), under rocks, and interesting commensals such as tiny almost translucent crustaceans that live on black coral trees.
Photos of crustacean, flatworm and nudibranch
It is difficult to count up exactly how many new critters we’ve found at the moment without more detailed study on each taxa. But for now, its clear that the marine biodiversity inventory of Ascension Island is still climbing, continuing to highlight the uniqueness of this marine biodiversity hotspot in the middle of the equatorial Atlantic.
By Simon Morley
One of my main jobs this year is to finish the assessment of the animals that live within the tile fish piles. There is a fish at Ascension, called the sand tile fish that builds mounds out of rubble and lumps of calcified algae. They live off the end of the larva flows on fairly flat gravel bottoms. So, to attract their females, the males pile up the pebbles and cobbles to form a mound. This mound has a tunnel underneath which acts as a nest hole for fish that successfully attract a female. On a flat fairly featureless seabed the piles are an oasis of living space for many small marine invertebrates and therefore provide an important boost to the local diversity. We are investigating what lives in these piles and finding some really neat crabs, shrimps and even a few sea slugs that we rarely see elsewhere.
By Juliette Hennequin
Dive surveys have started here in Ascension this past week-end with a highly motivated team of 10 divers, all keen to do their best to contribute to the project. After a lovely test dive Saturday, we achieved quite a lot in our Sunday dives, dedicated to collections.
The team was split according to the needs of the survey, some concentrating on macro photography, some on collecting samples, some focusing on Tile Fish piles. I know, this is intriguing, but don’t worry, we will come back to you and let you know more about these later…let’s just keep a bit of mystery for now!
In fact, it turns out 8 of us were scuba diving and the 2 other were spear fishing, trying to collect Rock Hinds, Squirrel Fish and Spotted Morays, the latter being the trickiest. I happen to have been on that team, and as much as it sounds nice and cool on paper, the activity turns out to be quite tricky, our fellow scientists having needs, you see! They actually want us to get them tiny little fish, which are not the easiest to spear, as you could surely imagine.
I will leave you for now and come back to you as soon as I can with some surely nice stories, and a few more photos!
A few SMSG & SAERI members are getting ready to fly out to Ascension to participate in a dive survey aiming to fill in the remaining knowledge gaps, building capacity and facilities at Ascension Island, and to enable the sustainable management of marine resources beyond the lifespan of the project.
The two SMSG/SAERI surveys planned for the AIMS (Ascension Island Marine Survey) programme are to augment the work conducted by the AIMS team, on the island, by filling in gaps in sampling, particularly in environments and habitats not yet sampled or under sampled.
A team of 15 divers has been put together, and responsibilities will be split between us to ensure we can get the maximum data out of the survey.
- Dr Paul Brickle – Principle Scientist
- Andrew Richardson – Principle Scientist
- Dr Paul Brewin – Principle Scientist
- Kate Downs
- Emma Nolan
- Dr Judith Brown
- Steve Brown
- Dr Rob Mrowicki
- Dr Simon Morley
- Dr Vladimir Laptikhovsky
- Peter Wirtz
- Steve Cartwright
- Jerry Pearce
- Dion Poncet
- Juliette Hennequin
The survey will be conducted over a period of just under 2 weeks, starting July 11th 2016.
A first team will leave the Falklands this coming Friday and join the members of the AIMS project already on Ascension. Diving should start immediately after a brief equipment check.
The past few days and the ones to come have been spent dealing with logistics for the trip, spreading the load we have to carry between us, and making sure nothing is left behind. It seems like we won’t be travelling light, as the survey requires us to carry some rather heavy pieces of equipment…but I won’t tell you more right now, you’ll have to wait till my next post to find out what exactly we are up to!
I will get back with fresh (or should I say warm?) news from Ascension next week!
By Emily Hancox
The final day for most of the team coincided with the annual fishing competition. We arrived at the pier at 11am, to be met with the first fishermen returning with their fresh catches, and a small crowd of spectators.
Large yellow-fin tuna
Being saved the effort of catching our own specimens, the team rapidly set up an array of scalpels, knives and forceps to process the variety of fish available. The goal was to collect length, weight, sex and maturity information, and to extract the fish ear bones (otoliths) for ageing purposes. A messy business at times, bystanders watched with interest as the borrowed hacksaw was put to use, sawing open fish heads to reveal the otoliths. A small crowd of children became willing assistants, holding little vials and offering enthusiastic advice as the blood, brains and bones occasionally proved challenging to work with. As the sun swang around to glare upon our previously shaded workspace, onlookers “oohed” and “aahed” as the first of the boats returned with their spoils. Huge tuna, the largest weighing 120kg, were craned on to the pier and winched into position to be weighed. After being professionally butchered and sliced into stunning chunks of meat, the heads were available for us, and the saw was back in action.
The species available for sampling were diverse, different jacks, dolphin fish, moray eels, and wahoo forming a part of the hooked fish that were brought to the table. Remnants of these, and those that were unwanted were rapidly welcomed by the blackfish in the water below.
As people retired to the Saints Club, samples were packed, gear was cleaned and packed, and preparations were made for our imminent departure.
Thanks to all who were involved!