摘要：In connection with the Norwegian Petroleum Directorate’s seismic survey off the coasts of Vesterålen
and Troms in summer 2009, the authorities wished to perform a research project aimed at improving
our understanding of how seismic campaigns affect fish distribution and the commercial fisheries. The
Institute of Marine Research was given responsibility for carrying out the project, which was financed
by the Norwegian Petroleum Directorate (NPD).
The aim of the project was to study the degree to which the species of fish occupying this area were
affected by seismic shooting activity, whether by withdrawing from the area or changing their
behaviour in other ways that affected the fisheries, and to document how long reductions in catch rates
lasted after the collection of seismic data had come to an end. NPD also wished to determine the
greatest distance at which the fish would react to the sound of the air-guns. The Directorate further
wished stomach samples to be collected in order to find out whether the fish changed their grazing
habits. A survey of the quantity and distribution of fish larvae and zooplankton in the area, and of
whether these changed during the collection of seismic data, also formed part of the objectives of the
project.
Seismic data were collected within an area of 8 x 46 nautical miles during a period of 38 days (June 29
– August 6, 2009). The seismic vessel “Geo Pacific” operated in accordance with standard procedures
for 3D seismic data acquisition. The study was carried out in Vesterålen (Nordland VII), where the
planned acquisition of seismic data overlapped with traditional fishing grounds for Greenland halibut
(Reinhardtius hippoglossoides), redfish (Sebastes marinus), saithe (Pollachius virens) and
haddock (Melanogrammus aeglefinus). The survey took place at a time when there are usually few
gadoids in the area, and thus relatively little fishing activity. Two local gillnet boats that fished for
Greenland halibut and saithe/redfish respectively were chartered, as were two local longline boats that
fished for Greenland halibut and haddock. The fishing trials commenced twelve days before the start
of seismic shooting, and continued until 25 days after termination of the data-acquisition programme.
The research vessel “Håkon Mosby” and the chartered fishing vessel “Eros” carried out an acoustic
survey of the distributions of fish and plankton in the area, in order to determine whether these
changed between before, during and after the seismic survey. Sound measurements were also made at
a range of depths and distances from the seismic air-guns. The dimensions of the seismic survey area
relative to topographical conditions and the sites of the fishing grounds made it impossible to
determine the maximum distances at which the fish would react to the sound of the air-guns.
The research project revealed that the sound of the air-guns affected the fisheries in the study area off
Vesterålen in a number of ways. These included both larger and reduced catches of individual fish
species, made by different types of gear.
Gillnet catches of Greenland halibut and redfish rose during seismic shooting and remained higher
after the end of the campaign than they had been before the start of seismic activity. On the other
hand, long-line catches of Greenland halibut fell during the seismic campaign, but rose again in the
course of the following 25-day period.
The results for saithe revealed a decline in gillnet catches both during and after seismic shooting, but
the differences were not statistically significant. The decline in gillnet catches of saithe was in
agreement with the acoustic survey estimates, which showed a fall in the quantity of saithe in the area
of the seismic survey and in the adjacent area closer to land, but the difference was statistically
significant only in the latter area, where the saithe were most abundant. These results were interpreted as an indication that saithe left the area in response to the seismic survey. The high degree of variance
in the data made it impossible to say just how long the possible reduction in catches of saithe lasted.
