Fish of the Aura River

Beneath the surface of the river, there is a rich and diverse world of life, even if it often goes unnoticed from the shore. The fish of the Aura River can be difficult to spot from the riverbank due to the murky water. However, in the reed beds along the shore, you might hear loud splashes as pikes hunt smaller fish. On a calm river surface, you can see ripples caused by fish rising to snatch insects from the water. In addition to insects, smaller fish feed on microscopic zooplankton. Fish form a highly diverse group and play a crucial role in the aquatic food chain. They also serve as an important food source for many birds feeding along the Aura River, and therefore their ecological significance extends above the water’s surface as well.

Finland is home to 105 fish species, although some are only occasional visitors to the country’s marine waters. The Aura River supports a rich fish population, with 38 different species recorded just below the Halistenkoski rapids. Some fish species live and reproduce in relatively small areas, while others migrate long distances to their spawning grounds. All migratory fish species in Finland are endangered. In the Aura River, migratory species include Atlantic salmon, brown trout, and whitefish. In 1995, a fish ladder was built at Halistenkoski, allowing salmonids to bypass the dam. The ladder consists of 22 gravel-bottomed pools that break the height difference into smaller steps. Thanks to the fish ladder, salmonids are able to ascend from the sea all the way to the Nautelankoski rapids in Lieto. In the future, the goal is to further improve migration and spawning opportunities for salmonids by restoring rapid areas and removing migration barriers.