Seismic vs. fisheries – better information can lead to less conflict. And we need to do more research on how seismicity affects pelagic fisheries.
The petroleum industry uses air guns – seismic – when searching for new or monitoring existing deposits of oil and gas under the seabed. Seismic is also used to monitor reservoirs for storing CO2 in the seabed, and to map suitable areas for the deployment of offshore wind turbines.
The air guns make a loud noise, and the echoes from the sound waves tell geologists about the sediments under the seabed. The sound also travels over long distances in the ocean and is easily heard by fish.
How are fisheries affected?
A new report has mapped out how seismics can affect fishing activity.
“There can be land conflicts, because seismic ships occupy quite large areas during surveys. Either because they drag long cables with sound receivers behind them, or because they place listening stations on the seabed that cannot be trawled over. The sound from the air cannons can also affect the behaviour of fish, and thus how easy it is to catch.”
This is explained by marine scientist Lise Doksæter Sivle, who has led the research project ‘FiskeriSeis’.
“Much previous research has focused on bottom fish such as cod and haddock. This project has shown that more research is needed on how pelagic fisheries are affected. Fishermen themselves highlight pelagic fisheries as particularly challenging, and they also often take place in the summer, when there is also a lot of seismic activity,” says Sivle.
Many people experience conflicts
“Many of the fishermen talk about land conflicts. This is not always clear in the reports from the fisheries experts who are on the seismic ships, because often there are no fishing boats to be seen in areas where seismic activity is taking place. But it could just as well be because the fishermen stay away from areas where surveys have been reported,” says Sivle.
Several fishermen highlight the problem that seismic surveys are often reported for large areas over long periods.
“Then it is possible that they stay away from the entire area for the entire period, even if the seismic activity is only taking place in smaller parts for limited periods of time,” says Sivle.
Better information can mitigate conflicts
A relatively simple improvement that could mitigate the conflicts is for the seismic company to provide information to the Norwegian Continental Shelf Directorate about exactly where they plan to use air guns in the next week. It should be specified whether tow listening cables or place nodes on the seabed will be used.
“This information must also be available for automatic download to fishermen’s chartplotters,” says Sivle.
Experiencing poorer catches
Fishermen report that catches are reduced in areas where seismic activity is taking place, which is why they often choose to avoid fishing where seismic activity is taking place.
“They say, among other things, that North Sea herring swim away, or that shoals break up into small schools, or that the swimming pattern becomes more unpredictable. This makes it more difficult to catch herring with a net,” says Sivle.
The marine scientist points out that there are otherwise large differences between species, life stages and habitats when it comes to how fish are affected by seismic activity.
“How behavioural changes in fish affect catches also depends on the type of gear. For example, net catches may increase if seismic activity makes the fish more active. Baited gear may yield poorer catches if the sound makes the fish less interested in grazing,” explains Sivle.
What do the catch statistics say?
The marine scientists have studied catch statistics from periods with and without seismic to gain insight into how seismicity may affect catch rates.
“We have looked at the Greenland halibut fishery with nets and lines, and the herring fishery with seines and trawls. These fisheries have been highlighted by fisheries organizations as fisheries with a degree of conflict in recent years,” says Sivle.
The catch statistics for Greenland halibut suggest that less fishing is done during periods with seismicity.
“This may be because fishermen avoid areas with seismicity. We must also emphasise that we did not have data on catch size , so we were unable to make any comparisons here.”
For the herring fishery, no difference was found between catch size with and without seismicity. There was also no demonstrable correlation between seismicity and the time fishermen spend looking for fish.
“We have now developed a good method for analysing the relationship between seismicity and fishing activity. However, we lack good data from periods without seismic, so the analyses of the herring and Greenland halibut fisheries should be repeated with larger data sets over a longer period of time to provide better insight,” says Sivle.
Dissatisfaction with the compensation scheme
There is a compensation scheme where fishermen can apply for compensation as a result of lost income due to the seizure of fishing grounds.
In the pelagic fisheries, there was great dissatisfaction with this scheme, which is related to the documentation requirements.
“To receive compensation, you must document a financial loss. It is easier if, for example, you fish with fixed gear in the same place at the same time year after year, and then have to stay away for a year, than if you engage in pelagic fishing with seines or trawls.
“Dynamic stocks such as North Sea herring migrate over large distances, and there can be several reasons for reduced catches and lost fishing time. If fishermen still reach their quota, but believe they have had additional expenses in the form of increased fuel consumption due to the seismicity, it can be challenging to get this documented, says Sivle.
“Several fishermen state that they see no point in submitting claims for compensation they believe they are entitled to, because it is almost impossible for them to document the claim,” she adds.
Better to measure sound level than distance
Previous studies with cod and haddock have shown that the sound from seismic can affect the behaviour of fish 20 nautical miles away.
“Sound modelling that we have done shows that bottom depth in particular, but also the type of seabed, has a major impact on how far the sound reaches. We saw, among other things, that at Eggakanten, where Greenland halibut is fished, the sound level at a given distance will be higher than at fish banks in the North Sea,” says Sivle.
The researchers therefore believe that measured sound levels are better suited than distance to assess how far away from the seismic the fish’s behavior can be assumed to be unaffected.
Reference
Lise Doksæter Sivle, Tonje Nesse Forland, Kate McQueen, Anne Christine Utne Palm, Kotaro Ono, Marte Louise Strømme, Geir Pedersen, Henning Wehde, Nils-Roar Hareide, Kristian Landmark Skaar, Nina Mikkelsen, Virgine Ramasco and Katie Dunning: « Effects of seismic surveys on fisheries – FiskeriSeis project report ». Report from marine research 2025-41
Image: Seismic survey in connection with a research project. Illustrative photo: Geir Pedersen / Institute of Marine Research (IMR)