The short version
- A research project by the Institute of Marine Research shows that fishing is a greater threat to life in the Outer Oslofjord than pollution and environmental toxins.
- The five biggest threats are fishing, environmental toxins, microplastics, physical impact and nutrient salts (from sewage and agriculture).
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The Institute of Marine Research (HI) has carried out a project, which shows that there are five main threats to marine life in the Outer Oslofjord:
The fjord area from Bastø by Horten on the west side, out to the two national parks Færder and Ytre Hvaler.
The biggest threats are in ranked order:
- fishing
- Environmental toxins
- Microplastics
- Physical impact
- Nutrient salts, including from sewage and agriculture
– The “big five” influencing factors account for 72 per cent of the total burden in our new risk assessment. They are on the worst list because they are widespread, occur regularly, originate from several different sources and can negatively affect several parts of the ecosystem, says researcher Johanna Myrseth Aarflot at the Institute of Marine Research (HI) to VG.
Cod warning
She says that there is danger for some species.
– The five mentioned have the highest risk of being negatively affected by human activity. Those that cannot be rebuilt immediately are bottom fish, such as cod, and eelgrass.
She says that they have not decided which ones measures which must be implemented – that it is what the politicians must do.
– Fishing has a social benefit that must be weighed against the negative effect it has on nature.
Here is an elaboration of the five main reasons
fishingIt is not environmental toxins or pollution that is the biggest challenge. It is human activity that affects the Outer Oslo Fjord the most, as we remove animals from the ecosystem through fishing – recreational fishing and commercial fishing.
Recreational fishing is very widespread in time and space. Lobster is an example of a species that is highly exposed to recreational fishing.
Commercial fishing is widespread for some species (such as shrimp) and takes place on a more limited basis for others (sprat).
Environmental toxins are a chronic influence for several parts of the ecosystem. There is an acute impact on fish larvae and fry, and originates from several sources in the Outer Oslo Fjord.
– We consider sewage and land-based industry to be the biggest sources of environmental toxins, but with significant contributions also from transport (ship traffic), agriculture, coastal infrastructure and tourism and recreation, says Aarflot.
Environmental toxins include pesticides, bottom material for boats, chemicals, pharmaceuticals and heavy metals.
Microplastics come from several sources, such as infrastructure, sewage, fishing activity (ropes and equipment) and leisure boats.
Since microplastics break down incredibly slowly, they just accumulate more and more.
The researchers assume that microplastics can negatively affect several species in the ecosystem, for example zooplankton and fish in early life stages. But the uncertainty is somewhat greater for how microplastics affect the environment than other factors.
Physical interventions in the beach zone or on the seabed cause direct damage to benthic fauna and flora. Examples are bottom trawling, anchoring, dredging, filling in and staying in the beach zone.
Eel grass is an example of an important habitat that has a high risk of being affected by physical interventions.
Benthic communities in the depths where trawling is done regularly is another example. There, the diversity of slow-growing species, such as corals, could disappear.
Fishing is the activity in the Outer Oslo Fjord that contributes the most to the risk of negative physical impact.
Nutrient salts are necessary for life in the sea, but too much of the good stuff leads to over-fertilisation and a bad environment in the fjord. The biggest sources are drainage (sewage) and agriculture.
Over-fertilization can provide unnaturally good conditions for phytoplankton (algae), which can have a negative impact on other parts of the ecosystem.
– We have systematized the knowledge we have available about all types of impacts on the ecosystem in the Outer Oslofjord today, says Aarflot.
She dispels the myth that the Oslofjord is dead.
– The Oslofjord is not dead, as you can read claims about, but there are parts of the ecosystem that are more alarming than others. This applies, among other things, to cod and eelgrass.
– Is there cod again?
– Bottom fish have a poor status and we are seriously worried about cod in particular. For cod – and demersal fish in general – professional and recreational fishermen are treated equally in our report, that is to say, we assume that they pose an equally great threat and that this is collectively the greatest threat to cod.
– Do we have to stop fishing?
– It is a political decision. We only show that fishing/harvesting is the biggest direct threat to coastal cod in the Outer Oslofjord.
She says that recreational cod fishing in this area is prohibited all year round.
– So the biggest threat to the cod is illegal fishing?
– The sum of recreational and professional fishing which is the biggest threat. Recreational cod fishing is illegal, but commercial fishing is not. It is a challenge that the ban is little known. We know that there is extensive fishing from recreational boats in the Oslo Fjord. There are over 400,000 leisure boats in the Oslo Fjord.
Aarflot says many fish illegally without knowing it.
– More recent investigations by the Directorate of Fisheries show in any case a lot of illegal fishing in the fjord, including in spawning areas for cod where all recreational fishing is prohibited between January and May.
In second place on the list of the worst are environmental toxins, for example from boats and ship traffic.
Microplastic is in third place.
– We have all heard about all the microplastics from car tires that eventually end up in the sea. But there are also over 400,000 leisure boats in the Oslo Fjord with a total of over five million days of use a year. Rough calculations show that the wear and tear on the hull, paint and bottom material while the boats are in the fjord adds over 50 tonnes of microplastics a year, says Aarflot.
Nutrient salts such as sewage and runoff from agriculture are also a threat, but more so further into the fjord.
– Such environmental toxins can affect many more groups by reducing reproduction. For young cod, eggs and larvae, environmental toxins are the biggest threat. They are sensitive to environmental toxins, she says and adds:
– There has been a great deal of focus on the need for sewage treatment in the municipalities around the Oslo Fjord. Therefore, you might expect a higher ranking for nutritional salts in our report. But we are looking here at Ytre Oslofjord, which has significantly better water exchange than inner parts of the fjord.
The research on the Outer Oslofjord is part of a larger project.
