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Fish protection enhance both fish stocks and marine environments

Last changed: 07 August 2023

Banning fishing has positive effects on fish stocks but also helps to restore the marine environment.

Scientists have evaluated of the long-term effect of Swedish no-take zones. The results show that the fish populations rapidly increase when an area is fully protected.

However, the positive effects may disappear within a few years, if a no-take zone is reopened to fishing.

More and bigger fish

  • Fish size and abundance increased rapidly when areas were closed to fishing.
  • On average, stocks in no-take zones tend to be three times larger five years into a ban, than compared to those in similar areas, where fishing is allowed to continue.
  • In the Baltic Sea it may be necessary to also regulate seals and cormorants, in order for the coastal fish stocks to recover.

Fish contribute to healthier ecosystems

No-take fishing zones benefits the marine habitats and can counteract negative effects of eutrophication.

More predatory fish will eat more of the smaller fish and decapods, whose prey survive better and increase in abundance. These small grazing invertebrates control the presences of epiphytic algea. This benefits seagrass and macoalgae, like bladderwrack, which form important habitats for other species.

Thus banning fishing has positive effects on more than just fish stocks. The measure can also restore the habitats of other marine species and create more well-functioning ecosystems.

"The results from the tests with no-take zones in Sweden are promising for stationary and local fish stocks. In order to see effects on fish that move across larger areas, as cod and herring, we need to do more and be patient. It takes a long time to rebuild collapsed fish stocks", says Mattias Sköld, one of the authors of the evalutation report.


Ulf Bergström, Researcher
Department of Aquatic Resources, Institute of Coastal Research, SLU, +46 10 478 41 17

Charlotte Berkström, Researcher
Department of Aquatic Resources, Institute of Coastal Research, SLU, +46 10 478 41 65

Mattias Sköld, Researcher
Department of Aquatic Resources, Institute of Marine Research, SLU
Ship Management Unit, SLU, +46 (0)10 478 40 46, +46 (0)705-37 87 74