I've just returned from seven days on board SV Vega as part of a small team monitoring the impacts of seismic testing on marine mammals off the west coast of Northland. No research has been done in this area, so I jumped at the chance to be involved.
We left from Houhora and rounded Cape Reinga. It took us an entire day to get out to the survey site and on the way our first mate Nick showed me how to steer the boat, which was important because we all had to take turns doing this during the trip. Twice on the way, we had dolphins come up and swim along side the boat. The next time we saw dolphins, we had hydrophones in the water recording close to where the Aquila Explorer was doing its seismic testing for Statoil.
Seismic testing involves a ship firing off repeated sound blasts day and night sometimes over weeks or months. The blasts, created by underwater cannons, generate a pressure wave that penetrates the seafloor and the reflected sound waves are then recorded by on an array of sensors dragged on long cables after the ship. Evidence from marine scientists around the world suggests that seismic testing negatively impacts whales and dolphins.
After that initial sighting, we didn’t see any dolphins again until we were on the way back, outside of the permit area. Even if we didn’t see many marine mammals, we could hear them on the recordings we got from our hydrophones. My colleague, marine scientist Matt Pine, was able to identify whales and dolphins by their sounds.
On our second night out, when we were drifting in the permit area, I heard something. I was lying in my bunk, falling in and out of sleep in the rocky boat, and I could hear a banging sound. I assumed the sound must have been a float hitting against the outside of the boat as we rocked in the waves. Surprisingly, the sound I was hearing was actually the seismic array. It was quite loud, even when the ship was just a very faint light on the horizon.
One night when I was on watch, Matt came running up the stairs with his hands full of cable ties, rope, and a hydrophone. It was 1am and he had been woken up by the sound of the array. The weather was awful, the boat was rocking violently, and we were both fighting seasickness as Matt fastened his hydrophone to a rope and held it over the side of the boat into the water for a few minutes to try to record the sound that had woken him up. Later, after Matt had analysed the data on his computer, he handed me his headphones to listen. Every five seconds, it sounded like a gun shot: chk-chk BOOM.
We had intended to stay out for three more days to get more marine mammal observations and additional recordings of the seismic array, but the weather was steadily getting worse, so we had to head for shore. Now that we’re home, we have hours of data that we will be analysing well into next year.
Heather Braid is a marine biologist based in Auckland.
Photos by Nick Tapp