Squid: lessons from the deep

Squid: lessons from the deep

Science | Environment

Pete Wilton | 18 Nov 10

A recent expedition to the Indian Ocean returned with a new species of squid and a haul of strange and unusual creatures netted from the deep.

I asked the expedition's Principal Scientist, Alex Rogers from Oxford University's Department of Zoology, about the team's bumper catch and what these deep-sea animals can tell us about ocean ecosystems, biodiversity and mitigating man's impact on our oceans...

OxSciBlog: How & where did you discover this new squid species?
Alex Rogers: The squid was captured on an expedition to explore the waters around the seamounts of the South West Indian Ocean Ridge. This cruise was undertaken on the RV Dr Fritjof Nansen as part of a wider IUCN project to examine the management of high seas fisheries in the southern Indian Ocean funded by UNDP and the GEF.

Seamounts are hotspots of biological acitivity in the deep oceans and we were particularly interested in what was driving these ecosystems, especially the populations of commercially fished species such as alfonsino, a large red deep-sea fish.

I was the Principal Scientist on the expedition and we covered a distance of 5000km observing the movements of animals in the waters around the seamounts using acoustics and then sampling the reflective layers we observed (deep-scattering layers) with a variety of nets. The new squid species was captured with an enormous mid-water trawl called an aakra trawl by the Norwegian crew of the vessel.

OSB: What were the challenges involved in identifying it as new?
AR: Identification of deep-sea fish, squid and crustaceans is complex and requires specialist knowledge. Squid, in particular, are only studied by a few specialists and they use a variety of features to identify species, such as the shape of the beak, the form of the tentacles and suckers, the shape of the mantle and cartilage within it.

To complicate matters further, the South West Indian Ocean Ridge, even now, is almost unexplored in terms of biology and biogeography. We therefore gathered a body of expert scientists to identify the material from the cruise in a workshop in South Africa funded by the Total Foundation and the Census of Seamounts Project [ CenSeam ]. We were extremely lucky to have a squid expert on the team, Vladimir Laptikhovsky from the Falkland Islands Fisheries Department. He had a very exciting week, identifying a fifth of the worlds squid fauna within our collection from the expedition, including the new chiroteuthid squid and possibly several other new species, although they will require further study.

The squid is a deep-water species and has some very unusual features in terms of its body shape and may even represent a new genus or even family. We also identified close to 200 species of fishes, some of which may also be new to science, but which will require further study by scientists.

OSB: What can this discovery tell us about biodiversity in the oceans?
AR: The deep ocean is poorly understood and yet is facing human threats from fishing, oil production, and climate change. There is even now a proposal to mine the South West Indian Ocean Ridge for minerals associated with deep-sea hydrothermal vents. This and the other discoveries of the expedition demonstrate that we have much to still learn about these myterious ecosystems.

This squid is not a small animal, it is several feet long, making it more impressive that it hasn't been seen before, especially given that squid are not particularly diverse as a group and have very wide distributions. It may also tell us something new about the evolution of this particular group of squid.

OSB: What do you hope you may find out of the other specimens?
AR: The samples show that communities across this part of the southern Indian Ocean vary considerably moving from north to south. They also show a major effect of the seamounts on the structure of the ecosystem. Our acoustic surveys appear to support a theory that seamounts act as giant traps for migrating layers of zooplankton and small fish, crustaceans and squid. This allows resident predators, including commercially valuable deep-sea species such as alfonsino, orange roughy and armourhead, to feast every day on these species as they migrate up and down in tune with dusk and dawn.

In South Africa we identified the members of the deep-scattering layers and sampled the stomachs of the predators we captured. These will provide the proof that these fish populations are being sustained in the way we have predicted. Contained in our marvellous haul of specimens are important data on the distribution of the fauna of seamount ecosystems and the wider communities of the water column, further new species, species newly recorded for the Indian Ocean, and information on the growth, reproduction and development of marine animals.

In other words this single expedition has made a significant contribution to our understanding of the ecosystems of the high seas. Next year we will return to the same seamounts on a NERC -funded expedition to explore the animal life living on the seamounts. This is even less well know than that of the water column and more exciting discoveries will certainly be made.

Image above: Alex Rogers with a rare specimen of a dealfish caught over the Atlantis Seamount. Photo: Sarah Gotheil.

Professor Alex Rogers is based at Oxford University's Department of Zoology.