Monitoring Blue Mussel distribution – Baseline survey for 2021 and 2022

Mussels (Mytilus sp.) are widespread along the entire coast of Norway. In the last 15 years, the Institute of Marine Research (HI) has received reports that mussels have disappeared from places where mussels were usually collected. In 2020, HI developed a method to monitor regional populations of mussels. The goal of monitoring is to clarify whether the mussel populations are changing over time. If the stock is changing, the monitoring will also provide a data set to uncover possible reasons for changes. The monitoring started in 2021 and has been carried out for four regions (East (Oslofjord), South (Agder), West (Hardangerfjord) and North (Tromsø). Within each region, 50 – 100 stations along the intertidal zone were examined. Each station covers about 100 meters of coastline. All stations were randomly selected and the occurrence of mussels was determined and logged according to the following categories: 2 continuous cover, 1 patchy distribution or 0 few or no mussels. This dataset covers the baseline surveys for the years 2021 and 2022, which shows that mussels occur in all regions, from the innermost fjord to the exposed coast.