Today marks the halfway point in our journey and we have started the demersal trawling part of the voyage. Each day has been full-on with excitement and new things to learn and see. The highlight of the last few days was holding one of the biggest fish in the Southern Ocean in my arms – an Antarctic toothfish. One the projects associated with the trawling is to gain information on the toothfish fishery, so any toothfish we catch are tagged and released. The small pin-like tags are inserted just behind the dorsal fin and, if the fish is re-caught, can give information on movement, growth rate, and abundance of the species.
On the morning of my third trawl we pulled up a small looking catch but with one obvious lump in the net. I thought this was just another substantial glacial rock but then the lump began to move and my heart leapt as the biggest fish I have ever seen emerged. I had seen photos of Antarctic toothfish, but the size of this one really took me by surprise. It was 151 cm long and 42 kg and it took both Richard and I to lift and carry the enormous fish flapping in our arms to release it head-first over the side. Amazing to see that, even though it came from 1500 m below us, it was in perfect condition. The tagging was quick, so only a minute or so after coming on board, the fish was swimming back down to the sea floor.
We have done seven deepwater trawls so far and each one has brought up about 30 different species of strange creatures adapted for life in the cold and constantly changing waters of the Ross Sea. Each species is identified, weighed, measured, and preserved for further examination back on shore. Some of the most interesting species are lanternfish, which make their own light with bioluminescent pores because the sunlight doesn’t reach them at great depths. We also found a baby colossal squid, and icefish which have anti-freeze in their blood so they can live in the sub-zero degree seawater.
Because of the remoteness of the Ross Sea there is always a chance of bringing up a new species or something that will take us by surprise. Our biggest surprise so far was catching a whale vertebra in the trawl. The bone was about one metre in diameter and gave me a different perspective on how big these creatures are! Small worms where found living in the bone which were of a species we wouldn’t have seen any other way. I couldn’t help but think what are the chances of finding these?
The trawl net takes about half an hour to descend the 1500 m to the sea floor and is trawled for about 1.8 km. We are trawling random locations, taking us all over the Ross Sea to get abundance and biodiversity estimates. Some sites area are inaccessible due to the thick ice floes still present.
The fantastic weather is still following us and we have seen more amazing sunrises and sunsets. The sea has been changing the past few days with strange little pancakes of ice covering the water as the new year’s sea ice forms. As if the week hadn’t been exciting enough a pod of eight killer whales came to inspect the boat last night – crossing the bow and then following us for half an hour! Zac might talk more about this in his blog.
BLAKE NIWA Ambassador 2014