Spatial and temporal drivers of gill pathology in Atlantic Salmon

In recent years, both the Scottish and global salmon industries have been negatively impacted by a number of gill conditions such as proliferative gill disease (PGD), amoebic gill disease (AGD) and complex gill disease (CGD), causing increased mortality and overall decline in production efficiency.  As a result, gill health has emerged as the key challenge to the salmon industry, highlighted in The Scottish Government’s Farmed Fish Health Framework (FFHF).

Gill health is routinely monitored by macroscopic scoring of gill arches for PGD, from 0 (no pathology) to 5 (severe pathology). As a part of the on-going SAIC project (NAGD), we demonstrated that the PGD scores from three different fish farms have no common underlying histopathology or molecular signature, suggesting either a lack of resolution in PGD scoring or a lack of mechanistic link between PGD scores and other parameters. Instead, the site effects were highly significant, with transcriptomic data matching histopathology. However, the site effects were confounded, because each site was sampled at different times of the year, making it impossible to distinguish between spatial (location) and temporal (season) causes of variability in gill pathology.

The current project aims to:

1. Identify spatial and temporal drivers of gill pathology
2. Further investigate the link between gross PGD scores and histopathological / molecular parameters
3. Design a panel of gill health biomarkers
4. Test the robustness of gill health biomarkers and efficacy of functional feeds to mitigate gill disease in both lower (Scotland) and higher (Tasmania) sea water temperatures.

The Tasmanian results may prepare us for environmental change facing Scotland, as highlighted in The FFHF Work Stream 7: Climate Change and Ocean Acidification.

Unlocking the mechanisms underlying the variability in gill pathology, generating novel diagnostic tools to monitor gill conditions and designing functional feeds to improve gill performance are essential to maintain healthy population of farmed fish, benefiting industry, consumers and environment.

Read the related press release here.