The Baltic Sea — A Unique Ecosystem

The Baltic's low salinity creates a biological bottleneck: only species that can tolerate brackish water survive. This means fewer species than a fully marine environment, but those present often form large, ecologically important populations.

Baltic Herring (Strömming (Baltic Herring))

The Baltic herring — called strömming (strömming) in Swedish (distinct from the Atlantic sill (herring)) — is the Baltic's most ecologically and culturally important fish. It forms vast shoals that are a primary food source for seals, seabirds, and larger predatory fish. For humans, strömming has been a dietary staple for centuries — and the base for surströmming (fermented herring), the notoriously pungent Swedish delicacy.

Cod (Torsk (Cod))

Baltic cod populations have declined dramatically due to overfishing, habitat degradation (low-oxygen zones in spawning areas), and shifts in food web dynamics. The eastern Baltic cod stock collapsed in the 2010s and remains at critically low levels despite fishing restrictions. The recovery of cod is one of the most pressing marine conservation challenges in Swedish waters.

Salmon (Lax (Salmon))

Atlantic salmon run in many of Sweden's rivers, migrating from the Baltic (or, on the west coast, from the North Sea) to spawn in freshwater. The largest wild salmon rivers are in the north — particularly the protected Torne, Kalix, and Vindel rivers. Hydroelectric dams have blocked salmon from many historic spawning rivers, and fish ladders and smolt releases are used to mitigate the damage.

Wild salmon angling — particularly fly fishing in the northern rivers — is a significant recreational and economic activity.

Seals

Sweden's coast supports three seal species, all of which have recovered from near-catastrophe.

Grey Seal (Gråsäl (Grey Seal))

The grey seal's recovery story is both a conservation success and a flashpoint of human-wildlife conflict. Fishermen along the Baltic coast report significant losses to seal predation and net damage, and a licensed hunt has been introduced to manage numbers.

Harbour Seal (Knubbsäl (Harbour Seal))

Harbour seals are most easily seen on the west coast — Kosterhavet National Park, the Gothenburg archipelago, and the Halland coast all host haul-out colonies where seals bask on rocks.

Ringed Seal (Vikare (Ringed Seal))

The Baltic ringed seal is a subspecies endemic to the Baltic Sea. It depends on sea ice for breeding — building snow lairs on the ice where pups are born. Climate change and declining ice cover are the most serious threats to this species, particularly in the southern Baltic where ice is becoming unreliable.

West Coast Marine Life

Sweden's west coast (Bohuslän, Gothenburg, Halland) faces the Skagerrak and North Sea, with fully marine salinity. This supports a much richer species diversity than the Baltic:

  • Lobster (Hummer (Lobster)) — European lobster; west coast speciality; hummer season opening in late September is a cultural event
  • Prawns (Räkor (Prawns/Shrimp)) — Coldwater prawns from deep Skagerrak troughs; the basis of räksmörgås (prawn sandwich)
  • Oysters — Pacific oysters have colonised the Swedish west coast (invasive, but now harvested commercially)
  • Crab — Brown crab and increasingly, invasive round goby
  • Mackerel (Makrill (Mackerel)) — Seasonal; summer shoals along the coast

Kosterhavet National Park, Sweden's only marine national park, protects the country's most biodiverse marine waters — including cold-water coral reefs, lobster habitats, and over 6,000 recorded species.

Freshwater Fish

Sweden's 100,000+ lakes and extensive river systems support a rich freshwater fish fauna:

  • Pike (Gädda (Pike)) — Top predator in most Swedish lakes; prized by sport anglers; up to 20+ kg
  • Perch (Abborre (Perch)) — Sweden's most popular freshwater catch; common in lakes nationwide
  • Arctic char (Röding (Arctic Char)) — Glacial relic species; cold, deep mountain lakes in the north
  • Trout (Öring (Brown Trout)) — Rivers and lakes; sea-run trout in coastal streams
  • Crayfish (Kräftor (Crayfish)) — The native noble crayfish (Astacus astacus) is endangered due to crayfish plague brought by the invasive signal crayfish. The kräftskiva (crayfish party) is an iconic August tradition.
  • Whitefish and grayling — Norrland rivers and mountain lakes

Threats to Swedish Marine and Freshwater Life

The primary challenges facing Sweden's aquatic ecosystems include:

  • Eutrophication — Nutrient runoff (nitrogen and phosphorus from agriculture, wastewater, and atmospheric deposition) fuels algal blooms and oxygen-depleted dead zones in the Baltic
  • Overfishing — Historical overfishing collapsed Baltic cod; herring and sprat stocks require careful management
  • Climate change — Warming water temperatures, reduced ice cover, and changing species distributions
  • Pollution — Legacy pollutants (PCBs, dioxins, heavy metals) remain in Baltic sediments and bioaccumulate in seals, fish, and birds
  • Invasive species — Round goby, signal crayfish, Pacific oyster, and others are altering ecosystems

Sweden participates in HELCOM (Helsinki Commission) and EU-level marine conservation efforts, and has designated marine protected areas covering significant portions of its territorial waters.

Swedish seafood cuisine — Herring, crayfish, and west coast prawns on the Swedish table

Kräftskiva — The August crayfish party tradition

Water resources — Sweden's aquatic systems as an economic resource