The purpose of monitoring coastal fish populations every year is to estimate the condition of different species. This is an important starting point for assessing ecological status in coastal waters, and for monitoring biodiversity.
The supervisor for the surveillance is the County Administrative Board of Västerbotten County and SLU, the Department of Aquatic Resources. Based on the results, the coastal fish stocks are estimated in aspect of variations in time and space, partly within each fishing area and partly between the various fishing areas.
Test-fishing in summer
The test-fishing is carried out in August each year in about twenty test-fishing areas in the South Baltic and the Gulf of Bothnia. Norrbyskärgården / Örefjärden is one of these provinces, and the area for which Umeå Marine Sciences Centre (UMF) is responsible.
Monitoring is done through fishing with Nordic multi-mesh gillnets, which have nine different mesh sizes. The nets are laid in different depth ranges at predetermined locations. Also water temperature and depth of view are measured. Species, length and weight of the fish are recorded.
For perch, some analyses are made, including gender and age. Perch and Baltic herring are sent to the Swedish Museum of Natural History for analysis of environmental hazards.