My discovery of the Dissostichus mawsoni

As the sun circled overhead, dipping gradually towards the horizon at midnight giving the windblown snow texture and an orange glow, the radio could be heard to crackle “Party to Scott Base, Party to Scott Base”.

It was the 11th December 1966, forty six years ago, and the field party was trying to make contact with Scott Base to ask how usual was it for Weddell seals to catch and kill large fish?

The reply came back through the static “We have fished all winter and the biggest fish we caught was 6 inches [15cm] long, how long is your fish?”

I could feel a sense of disbelief when I described a fish 147 cm long weighing 30 Kg. My colleague David Christoffel and I had rediscovered a fish which had been reported in 1905 by Robert Falcon Scott in his book “The Voyage of Discovery”. He had found the head of a large fish on the ice shelf. But little else was known about it.

Research showed that a similar fish named Dissosticus eliginoidesi, had been described by J.R.Norman in a paper describing fish of the Patagonian Coast, but these were much smaller reaching only 36cm in length. With assistance from others the seal’s catch was identified as Dissostichus mawsoni. And the details were written up in the New Zealand journal of Marine and Freshwater Research, 1969.(1)

Our 1966 fisherman

We identified this fish as an important component of the seal’s diet, but also found that Dissostichus mawsoni, had itself been feeding on the Pleuragramma antarcticum, which is a fish frequently devoured by the bird life such as penguins.

Thus Dissosticus mawsoni or as we now call it the Antarctic Toothfish, was seen to be a critical link in the food chain both upward as food for the seals, and downward as a predator of P. antarcticum.

As a scientist it is disturbing that following an exploratory visit in 1996, a commercial fishery has been set up to extract 3,000 tonnes without any definitive data to support such a quota.

If it took from 1905 until 1966 to discover the size and detail of Dissosticus mawsoni, and another 30 years to 1996 until it was discovered in large quantities, what assurance do we have that removing 3000 tonnes per year will not disturb the fine ecological balance?

As the modern re-discoverer of the Antarctic toothfish I implore the New Zealand Government to take a conservative stand and halt all commercial fishing in the Ross Sea until much more research has been carried out. This is the last untouched region in the World where we have the opportunity to study the wildlife in a relatively untouched habitat. Once destroyed it is gone forever.

Dr Ian Calhaem

* For more information read Dr. Calhaem’s original paper.


1 Some Observations of the Feeding Habits of a Weddell Seal, and measurements of its prey, Dissostichus Mawsoni, at McMurdo Sound, Antarctica, NZ Journal Marine and Freshwater Research, Vol 3, No 2, June 1969.

One thought on “My discovery of the Dissostichus mawsoni

  1. This was a pioneering study made possible by researchers who had their eyes open to phenomena that really weren’t part of their research but which nevertheless appeared important. And in this case, that is a YES. Along with this study, and a few more modern ones, we’ve been able to estimate the dietary importance of toothfish to seals using the McMurdo Sound data. Unfortunately, the opportunity for future work on this issue is now destroyed, at least where it is convenient in McMurdo Sound, unless persons think it valid to consider the new ‘baseline’ to be a valid representation of the Ross Sea ecosystem. The new Ross Sea ecosystem is one in which large toothfish are no longer the ecological force they once were….they are going, going and soon to be gone.

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