Priority marine feature surveys within the Small Isles MPA and surrounding waters

Abstract

The Small Isles Marine Protected Area (MPA) is one of Scotland's biggest inshore MPAs, covering more than 800 km² and containing a complex mosaic of habitats. The six-year survey programme (2012 – 2017) conducted by Marine Scotland collected imagery of the seafloor within the Small Isles MPA: 9,374 digital images and 3,690 minutes of high definition video footage. This imagery was analysed to determine baseline abundances of eight seafloor invertebrate species with conservation importance related to Priority Marine Features. These imagery data showed that the Sound of Canna provides important habitat within the MPA. There were sufficient data to model changes in abundance over time for two species in four survey locations. The abundance of the Tall seapen (Funiculina quadrangularis) reduced after 2014, whilst the abundance of the Northern sea fan (Swiftia pallida) was stable over time. The potential impact of bottom-contacting towed fishing gear on the distribution of the Tall seapen in the wider area of the Minch, Inner Sound and Sea of Hebrides was also investigated. There was no evidence that fishing activity caused reductions in seapen abundance. However the analysis was limited by the available fishing data, which was at a broader scale (over space and time) than the abundance data. Finer scale fishing data would be needed for future studies to assess the impact of fishing activities on the abundance of seafloor invertebrate species. The results of this study provide a more extensive biological baseline of the Small Isles MPA than previously available, including more survey locations and repeat surveys over time. The Small Isles dataset strengthens the biological evidence base underpinning the Scottish MPA network by improving our understanding of where species occur and identifying important locations for different species. The abundance data can help establish management measures to support an ecologically coherent MPA network by identifying where the abundances of some species, such as the Tall seapen, have reduced. Continued surveying of the Small Isles MPA and the surrounding region is discussed with respect to monitoring changes in species abundance over space and time and assessing the effectiveness of any future management measures.