Introduction
Temperature is the master abiotic factor for salmon growth. Atlantic salmon has a wide thermal range for growth, ranging from 12-18°C. Tasmania, which produces the majority of Atlantic salmon in Australia, is a global hotspot for ocean warming, and water temperatures exceed 18°C for extended periods during marine heat waves, which are predicted to become more frequent. Suboptimum water temperature and low dissolved oxygen (DO) are key drivers of reduced feed intake and growth during summer, yet their impact on salmon production biology remains poorly understood at the proteome level. This study used proteomics to investigate the cumulative impact of sub-optimum temperature and low DO on the growth performance and nutritional physiology of post-smolt Atlantic salmon.
Materials and Methods
A total of n = 1144 post-smolts with a mean weight of 419.4 ± 3.2 g were distributed across 12 indoor RAS tanks and were exposed to simulated summer conditions (19°C; 80% DO) followed by an autumn recovery (15°C; 100% DO) for 84 and 42 days, respectively. Liver and white muscle tissue samples were collected from targeted individuals for label-free quantitative proteomics (from known genotypic groups of the Tasmanian Selective Breeding Program) expected to show high, medium and low growth performance (n = 8 samples per group per time point; n = 24 per tissue per time point) after summer stress and autumn recovery, referred to as post-thermal and post-recovery time points, respectively.
Results
Proteomic analysis of liver and white muscle protein extracts identified ~6300 and ~1800 protein groups, respectively, and t-test analysis (FDR < 0.05) identified 3650 and 257 differentially abundant proteins (DAPs) between different time-points. Bioinformatic analysis of the liver revealed that proteins increased in the post-thermal group were associated with functional terms, including endoplasmic reticulum stress, proteasome activity, heat-shock response, antioxidant defence, amino acid catabolism, fatty acid degradation, carbohydrate metabolism, and oxidative phosphorylation Significant proteins included SERPINh1, previously identified as a key biomarker of thermal stress in Atlantic salmon (Mendoza‐Porras et al., 2024). In contrast, functional terms associated with the proteins increased in the post-recovery group included ribosome biogenesis, cholesterol, and unsaturated fatty acid biosynthesis. In white muscle, enriched terms were directly or indirectly related to protein turnover processes at both time points. Statistical analysis for high vs low performance groups identified 306 and 273 DAPs in the liver between timepoints, respectively, and 81 DAPs (p < 0.05) at both time points in the white muscle. Enrichment analysis revealed differential mechanisms across the groups tested in this experiment.
Conclusion
Overall, this study provides an improved understanding of the physiological mechanisms operating in Atlantic salmon under suboptimum environmental conditions, with protein turnover being the most differentially affected process across tissues. Our findings also indicate that post-smolt salmon have biological capacity to recover and achieve compensatory growth at the protein level. Additionally, proteomic signatures across different genotypic groups were identified, offering a scope for future research towards climate-proofing the selectively bred Tasmanian salmon.
References
Mendoza‐Porras, O., Rusu, A.G., Stratford, C. and Wade, N.M., 2024. Rapid detection of heat stress biomarkers in Atlantic salmon (Salmo salar) liver using targeted proteomics. Aquaculture, Fish and Fisheries, 4(1), p.e147. https://doi.org/10.1002/aff2.147