December 10, 2001
Hi Class,
Our survey flights were delayed by a day so that gave me an opportunity to have an experience that I would like to share with you. There is a group here on the base at McMurdo that is starting a study of the Antarctic Cod fish population. They are comparing differences in protein (a substance found in all animals) between fish found here near McMurdo with fish found near New Zealand. Differences in the fish protein would be expected because of differences in the environments they live in.
Today they invited me to go along with them and learn how they catch these cod and study them. Also, today was to be a little different than their usual operation. They usually catch and release the fish after taking some sample fin and scale for study and then tagging them so that scientists can learn more about the general movement of these fish. Today, however, they were to bring two fish back for study at the aquarium located at McMurdo. Any additional fish caught would be sampled and released in the usual way.
We started by dressing warmly in our cold weather clothing because we were to ride on a skidoo (snowmobile) for a distance of about 6 miles. This photo shows the two skidoos that we would be using. The two research scientists from the Arizona State University would be driving. Henry, who is in Antarctica as an artist, is seated on the back of the one skidoo. I would be riding on the other skidoo. After about a 15 minute ride across the frozen ocean we arrive at their fish house (seen behind the skidoo) where they catch the fish. This photo gives a better look at the outside of the fish house. Inside the fish house you can see the four foot square opening cut in the floor. Beneath the opening is a large four foot round hole cut in the ice as you will see on later photographs. In this photo, you can see Mackenzie filling a capture container with cold ocean water dipped by bucket through the opening in the floor. The container was being filled in preparation for carrying a large cod fish for the aquarium. She later filled a second capture container. A cable that was 450 feet in length with an anchor at the end had been dropped through the hole in the ice the evening before. The cable had 12 large hooks attached to it at approximately equally spaced intervals and baited with a fish called mullet.
Soon a Spryte arrived with the remaining scientists and equipment. A Spryte is an all track vehicle for moving across ice and snow. The Spryte was next backed to the door of the fish hut for unloading. Meanwhile, inside the fish hut Gretchen prepared the winch that is used to pull the heavy cable into the fish hut. Near the ceiling was a block (pulley) over which the cable would be pulled. Notice the meters at the top of the cable that indicate the length of cable still in the ocean. Gretchen soon started to winch in the cable while Ali stood on a platform just above the hole in the ice guiding the cable away from the platform with a notched piece of wood.
At first we did not have any luck. The first seven hooks had bait still attached or hooks where the bait had been "cleaned off" by the fish. I was beginning to think that I had come for nothing except perhaps the skidoo ride, but the scientists were confident saying that the bottom hooks usually caught the most fish. Finally, we pulled up a hook with an Antarctic cod on it. And what a fish it was! It was huge and took both Brad and Ali to lift it from the hole in the ice. They first laid it on the large measuring board It was over 5 feet in length. After carefully removing the hook they placed the fish (still on the measuring board) upon scales and weighed it. The large cod weighed 93 pounds.
They are aso studying the DNA (genetic code) of these fish. Sean than cut a small piece of the tail fin for use in the DNA analysis and carefully stored the sample for later use in the laboratory. They then lifted the fish and placed it in the one transfer tank. It nearly filled the tank. We then resumed winching the cable. Soon we had another cod, though considerably smaller than the previous one. This fish was weighed, measured, sampled, and placed in the second transfer tank for transport to the aquarium at McMurdo. We then found another cod of about 35 pounds on the next hook. After completing the weighing, measuring, and sampling process on this fish, the scientists applied tags to the dorsal (top) fin and tail of the cod. Can you see the tags? If you look closely, you can see the blue tags near the front of the dorsal fin and near the top of the tail.
These tags are placed on the fish to aid scientists in understanding their travel habits. If these fish are ever recaptured by a similar study or by a commercial fishing boat, the information would be sent back to the scientists. Although this technique works well in some places in the ocean, it has only met with limited success here in the Ross Sea due to the remoteness of this part of the world. Although different programs at McMurdo have been catching, tagging, and releasing cod over the past 25 years only 13 have been recaptured, all by commercial fisheries. The remaining hooks on our cable were found to be empty and finally the anchor was hoisted above the hole in the ice.
The transfer tanks were next transferred to the Spryte for transport back to the base at McMurdo. I then rode back on one of the skidoos. As we were moving along I snapped a photo of the skidoo ahead of the one on which I was riding. On the way, we could clearly see Mt. Erebus, Erebus the volcanoe that is near McMurdo. Mt. Erebus is an active volcanoe that is 12,500 feet high.
When we returned to the Crary Lab at McMurdo, the Spryte was backed up to the loading dock. The two transfer tanks containing the fish were transferred from the Spryte and into the lab. The scientists then lifted the two fish into a large tank and released them. These scientists seemed pleased as the larger of the two cod swam by them in the tank
Regards,
Robert Swift