Norwegian researchers are taking a step closer to understanding Sandeel in the North Sea in a new report
The Norwegian Institute of Marine Research has published the report it has sent to the Norwegian Environment Agency on the status and vulnerability of sandeel in the country’s waters.
The small fish is of great importance to the ecosystem in the North Sea and is the cause of several “particularly valuable and vulnerable areas” (SVOs) on the map. They are sandbanks on which sandeels spawn and grow.
HI has now created an updated knowledge status of the sea herring, the most important sandeel species, on behalf of the Norwegian Environment Agency. They regularly process applications for oil activity near sandeel areas.
The marine researchers at the Norwegian Institute of Marine Research (HI) believe they have seen progress with stock in the south but have concerns about stocks further north on Vikingbanken.
“The sandeel has recovered from poor to good status in the south of the Norwegian economic zone in the North Sea. In the habitat further north, it has not managed this,” says marine scientist, Espen Johnsen.
Sandeel is not back in the same amount either along the coast or on the AlbjørnLing and Norgyden fields. But Johnsen is aiming first and foremost at Vikingbanken in the far north, which is in a poor state for sandeel.
After bad times for sandeel, Norway introduced a new national management of the species from 2011.
At that time, the Norwegian zone of the North Sea was divided into several sandeel areas based on knowledge of the stock. The area got its own sub-quotas, and most important of all: Parts of a quarter of the area are always closed to fishing. This ensures that there are fish left to keep the stock up on the various sandbanks. The measures have generally worked well, with one major exception for Vikingbanken.
The scientists have been looking at heavy industry in the Vikingbanken area and believe that it may provide another link with the decline in local sandeel.
“There may be several reasons for this, for example that the area was fished completely empty, so that there is simply no sandeel left to rebuild the stock”, says Johnsen.
But other types of human activity may also be part of the explanation.
“Vikingbanken is far more burdened by petroleum activity than the other areas,” adds colleague and co-author Bjørn Einar Grøsvik. He is an environmental chemist and has done a lot of research on oil exposure of fish.
In the report, the researchers point out that Vikingbanken is located downstream of the Tampen area, which includes many of the large oil fields.
The report claims that Tampen is responsible for “chronic” pollution, with the oil field accounting for 828 tonnes of crude oil entering the marine environment each year. Tampen accounts for 45 per cent of the emissions of produced water on the Norwegian shelf, or around 57 million cubic meters every quarter. Since produced water contains small amounts of oil, this corresponds to 828 tonnes of crude oil directly in the sea. In addition, there are British emissions.
“Produced water contains some of the same substances we find in oil, such as BTEX, PAH, heavy metals and production chemicals. We have seen that haddock on Tampen has traces of oil impact on the liver,” says Grøsvik.
“Both sandeel and haddock live by the seabed. The sandeel likes to dig into the sand where it also lays its eggs.”
The research believes that this is affecting sandeel eggs.
“When it comes to oil pollution, we know from other species that the risk is highest for eggs and fish larvae. This will especially apply to sandeel, since both eggs and larvae lie relatively stationary in the sand where unwanted substances can accumulate over time,” he continues.
HI has previously shown that haddock eggs are more vulnerable to oil than, for example, cod eggs. The day is more sticky. Oil droplets adhere to the shell more easily.
“We have not done oil tests on eggs from sandeel, but we know that these are also sticky to be able to stick to the sand,” says Grøsvik.
In the report, the researchers put forward a possible hypothesis that sandeels in areas with high oil activity have lower survival and reproduction over time.
“But there is a lot we do not know. To find out if such a hypothesis can be true, we must experiment with sandeel oil at different stages of life. Then we have to look at both acute effects and long-term effects,” says Grøsvik.
Furthermore, the researchers highlight a number of other risk factors for sandeel:
Sandeel depends on a special type of gravel on the seabed. It must not be too coarse, nor too fine.
Installations, digging or changing the bottom itself could damage the sandeel.
“There may be sub-sea installations for the oil industry, but also wind turbines that are either anchored or planted in the bottom. These seize the area, and the construction can also ravage them,” says Grøsvik.
Sandeel is vulnerable to rising sea temperatures: With higher temperatures, plankton species in the North Sea are being replaced by less nutritious “relatives” from the south.
“But unlike other fish species, the sandeel cannot move – he is to a certain extent “landlocked” on his sandbank, as far as we know,” Espen Johnsen explains.
And an important part of the knowledge summary is to establish even what we do not know about sandeels.
The biggest unresolved question is to what extent the various sandeel areas in the North Sea exchange eggs, larvae and fish. In good sandeel years, there are also a lot of fish on the coast that the researchers do not know exactly where they come from.
They can be larvae that drift from the sea, or their own, coastal populations.
“Together with the Norwegian Environment Agency and several oil companies, we have applied for money for a new research project on sandeel. There we will close the knowledge gap so that we can provide a better risk assessment of the total load the sandeel and its prey are exposed to from fisheries, industry and climate change,” he concludes.