Investigating spat mortality in Scottish farmed blue mussels (Mytilus edulis)

Abstract

Mussel spat in Loch Eil, Scotland, experiences alarmingly high mortality rates. This study investigates the underlying causes through field surveys, environmental monitoring, and controlled experiments. Mortality in Loch Eil reached 68.3%, significantly higher than the near-zero mortality observed in Loch Sunart. Environmental analyses revealed distinct differences between the lochs, including variations in temperature, salinity, and heavy metal concentrations. Potential pathogens, including Photobacterium spp. and Vibrio spp., were identified. Controlled experiments demonstrated significant impacts of water quality, salinity fluctuations, and UV exposure on spat survival. Cohabitation experiments highlighted the potential role of genetic variability in determining spat resilience. This research provides crucial insights into the complex factors driving high mortality in Loch Eil mussel spat.