The Group continued survey efforts over the during winter 2007, at times diving in some challenging conditions, mainly concentrated around the Falkland Islands Government Nature Reserve, Kidney Island, in Berkeley Sound. We would like to share a few of our winter highlights with you.
The spectacular carnivorous flamed nudibranch or seaslug Aeolidia papillosa.
While diving around Kidney Island in June we came across our first flamed sea slug (Aeolidia papillosa) and witnessed a rather interesting behaviour. This nudibranch or sea slug, which is essentially a shell-less snail, is known to prey upon the small sea anemone Antholoba achates. As the nudibranch made its first attack the anemone detached from its rock and floated away in the current. After a little research back in the lab we found some literature reporting on this same unusual escape behaviour in southern South America.The small sea anemone Antholoba achates which is able to detach itself to escape enemies such as the flamed nudibranch. These small flattened crustaceans (Acanthiserolis schythei) are a common sight on sandy bottoms around the islands.
This winter we also managed to identify a second species of serolid isopod. These small crustaceans with flattened bodies look a little like fossilised trilobites. They occur all around the Southern Ocean from the shallows to the abyssal depths. Although we knew there were two species inshore it was not until this winter that we confirmed the identity of the second one. Acanthiserolis schythei is the larger and most common species in the inshore waters of the Falkland Islands whereas Cristaserolis convexa is smaller and has a smoother rounded shape. Both inhabit sandy bottoms to a depth of about 40 m and are most common at depths of less than 20 m. Males and females of both species can be commonly seen riding “piggy back” in a mating clinch. Younger/smaller Acanthiserolis schythei can sometimes be found in rock pools. Both species are important to the ecology of sandy/muddy environments as they are scavengers and thus aid nutrient cycling.Cristaserolis convexa is a smaller species of serolid isopod which we were able to identify this winter. Enormous schools of young Falklands sprat block out the sun on one dive around Kidney Island.
We also witnessed a huge abundance of the young of the year Falklands sprat (Sprattus fuegensis) schooling around Kidney Islands being preyed upon by dolphins, seals, gulls and penguins. The seals and penguins caused the schools to change shape as they went through the middle of them trying to pick off the unwary few. This is a very abundant species and young of the year are commonly found inshore before recruiting to adult populations in the Falkland Islands. Fisheries Department scientists have seen schools as high as 60 m and in excess of 100 tonnes on their scientific acoustic equipment during research cruises.
These sea cucumbers, which can be found all around the islands, keep their offspring close until they are able to fend for themselves.
One of the challenges we face is identifying some of the animals we see. This is mainly due to their limited distribution in the Southwest Atlantic. If the distribution doesn’t extend into the Pacific then it is unlikely to be reported in any of the South American literature. It is this lack of readily available information on species found in our region that we aim to address with the publication of the Falkland Islands guide to the shallow marine life. One example of a species which is quite common to our waters yet is very difficult to find in the published scientific literature is the sea cucumber Cladodactyla crocea. This echinoderm, which is related to starfish and sea urchins can be found to a depth of 100 m but is most common inshore at depths of less than 30 m. It is a hermaphrodite with both male and female reproductive systems and a brooder meaning it keeps its babies on its body until they are large enough to fend for themselves.
Over the next few months we will continue our work around Kidney Island and in Port William both on the beaches and rocky shores as well as underwater to depths of 20 m. Later on in the Spring we will conduct an ambitious series of diving expeditions to collect specimens and photographs around Beaver, Weddell and New Island on the RV Damien II