Taw Torridge Subtidal Mussel Assessment 2021 dataset https://portal.medin.org.uk/portal/start.php?tpc=010_86afa681ad7865cba8d8f8f4b82a6d2b To expand on the 2020 DSIFCA Taw Torridge subtidal mussel survey, a side scan sonar (SSS) and grab survey was carried out in 2021. This was undertaken to gain a better understanding of the extent of the subtidal mussel beds. As this was the first time DSIFCA have used the SSS methodology, proof of concept was a secondary objective of the project. A Tritech SeaKing Towfish SSS was deployed on the 14th October 2021 for a total of 13 transects of different lengths throughout the Estuary. This data was then analysed to plan the grab stations for ground-truthing the SSS signature, with 45 grab stations being identified. A total of 89 grabs were carried out across the stations on the 15th October 2021, with an Offset Day Grab with a sampling area of 0.1m². The survey was carried out by a DSIFCA and a Cornwall IFCA officer on board a local fishing vessel. Data includes georeferenced SSS tracks, georefenced grab success/failure, count of mussel in each grab and mussel length data for all mussels collected in grabs. 20210118