Fish spawn in the spring
The spring sun softens the ice covering Airisto and the coastal waters of Ruissalo, which is eventually broken up by wind. This allows sunlight to penetrate the water and start warming it up. This is the moment that fish have been waiting all winter – soon it is time to spawn. Pike (Esox lucius) are the first to arrive in the warming coastal shallows, spawning in April–May. Perch (Perca fluviatilis) spawn later in slightly deeper waters, and Baltic herring (Clupea harengus membras) have their own established spawning places in the outskirts of Airisto. Zander (Sander luciaperca) are not in such a hurry, waiting until the cusp of summer in June before spawning.
Not all fish spawn in the spring, however; brown trout (Salmo trutta) and Atlantic salmon (Salmo salar) swim past Ruissalo and into the River Aura during the summer and early autumn and do not spawn until reaching suitable places in rapids in the autumn.
The Baltic herring’s spawning is the highlight of spring in Airisto. Schools of herring arrive from the outer archipelago to spawn in their spawning sites near the shore, which stay the same year after year. This is why traditional fyke net fishing is still practiced here. Unfortunately the Baltic herring’s reproduction has been negatively impacted by the eutrophication of the inner archipelago and the contamination of spawning grounds.
