Without larval fish and production areas there would be no large fish. Successful reproduction has a crucial impact on the size of the fish population and determines the size of the age group.

Because fish eggs and larvae are extremely sensitive to changes in the environment, conditions during the spawning and larval season must be optimal. By safeguarding the reproductive phase, we can continue to enjoy good catches.

The reproduction areas (i.e. spawning and larval areas) of most fish species found in the northern reaches of the Baltic Sea are located at a depth of a few metres in shallows. Also juveniles often use the same shallow areas. The reproduction areas are typically limited compared to the entire distribution area of the species. Such shallow coastal waters are also areas affected by human activities and environmental loads. Eutrophication and silting, coastline construction and dredging pose a threat to the limited number of reproduction areas.

Luke’s maps of fish production areas provide an important planning and protection tool

Using field surveys and modelling, the Natural Resources Institute Finland produces maps on important fish reproduction areas in the coastal waters, specific to certain fish species. Surveys covering the entire coastline exist on all of the most important species of commercial fish species in Finland, including perch, pikeperch, sea-spawning whitefish and Baltic herring. Luke also produces data on the spawning time requirements related to certain environments, and develops cost-effective field and modelling methods.

Maps indicating the locations and quality of fish reproductionareas are an important tool both for the spatial planning and protection of marine and coastal areas and the sustainable management of fish populations. Data on reproduction areas are required for assessments of the environmental impact of various projects which alter the coastal environment, such as ports, sea routes and windmill parks.. Using such data, assessments can be made of the need to protect fish reproduction areas or issue fishing restrictions during the reproduction season. Data on reproduction areas can also be used to direct fish stocking towards the desired areas.

The key parties using such data are the environmental authorities, HELCOM, the fisheries administration and the owners of water areas.

Picture on top of the page: Lari Veneranta, Luke