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Journals 2003/2004

Elizabeth Gibbs
Thompson Middle School, Newport, Rhode Island

"Impact of human activities on dusky dolphin behavior and population biology"
Field Station, Kaikora, New Zealand
July 13 - 25, 2003

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Thursday, July 17, 2003

As expected, it was still a bit rough, so we went north to Marlborough Sounds, launching the boat in the town of Picton, not far from the dock for the ferry to the North Island. We traveled south down Queen Charlotte Sound and after about 15 minutes saw a crowd of several hundred shearwaters-birds-on the surface and several gannets nearby. Sure enough, there were fish, and with the fish, two dolphins.

While fishing methods between dusky populations in Argentina and New Zealand were once thought to differ, it appears that it's the physical environment that really determines their behavior in feeding. Dolphins in Argentina cooperate to chase fish into schools, then take turns dashing through the "bait ball" and eating while the others keep the fish contained. Dolphins off Kaikoura feed at night, over deep water, when plankton and therefore fish rise to the surface. It was therefore believed that the two regions had totally different fishing styles. However, in the shallow waters of the Marlborough Sounds, such as in Queen Charlotte Sound and Admiralty Bay, they feed the same way they do in Argentina. So we were lucky enough to see the feeding, although we didn't actually see them feed.

Most of our time spent in Queen Charlotte Sound was spent "scanning." Since there were seven of us in the boat, we could see quite a big area if we all looked off in opposite directions. We moved along at about 11 or 12 knots, which feels fairly fast. All around us rose steep, green hills that drop right Down to the water. It's a truly truly beautiful place.

Next we came upon a group of five adults and-a big treat-a calf, all traveling together. Another major difference between here and Kaikoura is the size of the groups in which dolphins travel. In Kaikoura they can be in very large pods. Here they are seen in much smaller groups. They are also far less conspicuous because they are often feeding in the day, and because they are in smaller groups, we're much less likely to see them engaged in spectacular leaps.

Next, Mika spotted four dolphins, which got away from us right away. We came upon a fourth pod (a "pod" of two) and they escaped pretty easily too. We continued for about 40 minutes as the sun sank behind the hills and then we pulled the boat out and cleaned it, as we did every day after using it. We scrubbed down the floor and the sides and rinsed it with fresh water.

Each time we saw the dolphins, Tim snapped pictures using a long telephoto lens. Between sets of pictures, he would shoot a "blank"-a picture of a person or object clearly not a dolphin-to separate the pods. We also recorded time, latitude and longitude (Queen Charlotte Sound is 418, the same latitude south that Rhode Island is north; Kaikoura is 42 south), temperature, salinity, turbidity, and wind speed and direction. The sound was quite salty, up to 38 parts per thousand. Ocean water is generally 35 parts per thousand.

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