Seismic noise and its effect on the distribution of cetaceans in the Vestfjord 12.07.2012
Ocean Sounds, Henningsvaer Norway
Max Planck Institute for Dynamics and Self-Organization, Göttingen Germany
During my daily research trips in the Vestfjord I observe many different whale species during the summer time. Many of these whales migrate many thousands of kilometres to reach sub arctic waters to feeding on plankton and fish. Humpback whales and fin whales are often seen with their 2-3 year old calves, to which plenty of food is important for survival. The mothers need to feed in order to produce enough milk for their calves.
Other whale species that are frequent visitors in the Vestfjord from May to September, are long finned pilot whales, killer whales, Atlantic white sided and white beaked dolphins, minke whales and less frequent sperm whales. Small harbour porpoises live locally close to shore all year round in the Vestfjord. That means that the Vestfjord is home and feeding place to at least 9 different species of cetaceans.
The prey species consumed by the whales differ greatly from zoo plankton eaten by fin, humpback and minke whales, to schooling fish like herring and mackerel eaten by almost all whales, and deep sea squid eaten by long finned pilot whales and sperm whales, as well as salmon eaten by killer whales.
It shows that the Vestfjord has a complex working ecosystem with many different species interacting. Any human influence will have a negative impact on the well functioning of this ecosystem.
Ocean Noise has been long regarded as a major threat to whales, due to the masking effect of their own communication signals. All whales depend on underwater sounds for communication in order to keep contact between individuals, especially for close mother calf bonds, to find food and inform others about it, to find mates and avoid predators.
Killer whales and pilot whales live in complex close social groups, so called matrilines, in which group members stay together all their lives, sometimes for over 80 years. These whales have evolved a complex communication system and rely on a quiet sea to be able to understand and transmit their calls.
Ocean noise mainly comes from boat noise, but a boat moves and the noise comes and goes. Other acoustic noise sources are naval sonar, which is directed sonar and even though the sound source is very loud and damages the whales, they have the possibility to move out of the sound beam. Another very loud noise source is seismic acoustic activity, which the oil and gas industry uses to find new resources in the seafloor. These signals are send out periodically over many days and weeks and they are omni directional and can be heard over a distance of more than 200km. When it comes to seismic activities the whales have no other chance than to move more than 200km away and stay away, basically have to leave their feeding and breeding areas for good if they want to avoid the noise.
Seismic activities have been allowed by the Norwegian government and supported with 260 mil krones this year. However, no thorough research on the impact on marine wildlife has been conducted.
For the last 4 weeks the Vestfjord was full of marine live. Mackerel schools came and many different whale and dolphin species were seen. More than 100 pilot whales were visiting the fjord, several humpback whales and fin whales were seen. Last weekend, on the 10.07.2010 I recorded strange but faint noise and sperm whales clicking inside the Vestfjord. Sperm whales are rare visitors and my first impression was that something was wrong. The last time I have heard sperm whales inside the Vestfjord was in 2010 at the same time when seismic surveys were taken place on the outside Ocean. On the 11.07 many humpback whales and killer whales, as well as pilot whales were seen inside the Vestfjord.
However on the 12.07.2012 I searched the Vestfjord and did not find a single whale or heard their calls. But what I recorded instead were loud periodic signals from the seismic surveys that have started the night before in an area called Nordland, which is a bit offshore from Bodø.
The start of the seismic noise correlates with the disappearance of the whales. If the whales were displaced from their feeding and breeding grounds due to the noise, it will have a negative impact on their feeding and breeding success which in return may reduce their long term survival.
Underwater sound recordings were conducted from a zodiac RIB boat with a TC4032 Reson hydrophone, custom build ETEC preamplifier on to a Sound Devices recorder with a recording range from 0-120 kHz.
Whales use a wide range of frequencies for communication; baleen whales use low frequencies of 17-20 Hz to communicate over long ranges (several thousand km) in the sea, humpback whale songs have their main frequency 70-300 Hz and dolphins and killer whales use communication and echolocation signals from 100 Hz up to 75 kHz.
Spectrogram (made with Avisoft):
This spectrogram shows a series of seismic airgun signals recorded 12.07.2012 outside Henningsvaer in the Vestfjord. Seismic airgun signals are periodically repeated in an interval of 9 sec and contain most energy in the low frequency range at 200 Hz.
The seismic noise was recorded in the Vestfjord on two different locations:
12.07.2012 Time: 13:46 Location: N68 05.616 E14 26.931
12.07.2012 Time: 14:14 Location: N68 07.823 E14 42.006
And heard it outside Henningsvaer at 17:22 o’clock.
Please find attached to this letter a sound file with the seismic airgun signals from which the spectrogram was created.
A study with experimental sound exposure to singing humpback whales showed a clear decline in vocal activity with the sounds being transmitted over 200km away. The test sounds were low in frequency and intensity, overlapping the whale song in the frequency range 400-900 Hz. The authors strongly suggested that in addition to studying short term and immediate effects of noise to cetacean communication and behaviour, also longer-term, larger scale monitoring of anthropogenic sound is necessary (Risch et al., 2012).
In our case humpback whales, fin whales and minke whales were present in the seismic noise area. The frequency range and explicitly the area of main energy (200 Hz) of seismic signals will mask vocal communication of those whales. Humpback whales communicate between 400-900 Hz, Fin whales at around 20 Hz and Minke whales from 30–450 Hz.
If whales are unable to communicate and keep contact with each other, they may be forced to move out of the noisy area and find new feeding and breeding patches. This will disturb their natural feeding and migration pattern. In addition repeated seismic airgun activities (as in the case of Nordland / Lofoten, last surveys were conducted 2010) will cause a long term avoidance of these areas, which in turn will not only influence their rate of feeding and breeding successes, but also influence the local tourist industry that rely on high biodiversity and healthy ecosystem (e.g. whale watching and other nature based activities).
During the past 3 years due to global warming of the ocean, new species of fish, such as mackerel has come into the Vestfjord. This attracts many whale and bird species to feed on them. Such changes in the local ecosystem should be taken into account when planning acoustic surveys or naval sonar exercises in such a deep and enclosed fjord as the Vestfjord.
I therefore urge the Norwegian government to stop these activities immediately and support and conduct research project to investigate the long range and long term effect of underwater noise, such as naval sonar and seismic activities and create rules for their protection before introducing such harmful human activities.
Please listen to 2012-07-12-seismic-Vestfjord-HVester