Introduction
Fish transport is a widely used and unavoidable essential practice in aquaculture for purposes such as stocking , breeding , and growth . However , this process often exposes fish to acute stress, which can significantly affect their physiology and overall welfare . The severity of transport-induced stress can vary depending on the initial health status of the fish and transportation conditions , including duration , stocking density , temperature , water quality , and ammonia concentration . While transport rarely causes immediate mortality , secondary and tertiary stress-related responses can compromise both specific and nonspecific immunity , increasing susceptibility to disease and osmoregulatory imbalances , which may lead to mortality . Current methods for assessing immune and health status rely on invasive procedures (e.g ., blood and tissue collection ). Established welfare indicators , which help assess how well fish needs are met , are often observed too late to enable timely intervention , and remain limited for many farmed species . Further research is needed to understand how common aquaculture practices , such as transport , impact farmed fish.
Experimental design and methodology
To investigate the molecular signatures following acute stress, three key European aquaculture species – Atlantic salmon (Salmo salar , AS), European seabass (Dicentrarchus labrax , ES), and rainbow trout (Oncorhynchus mykiss , RT) were submitted to transport induced stress. The transportation trials were designed to simulate current transport conditions specific to each species . Skin tissue samples were collected at three time points : before transport , immediately after stress exposure , and following a 24-hour recovery period . RNA sequencing (RNA-seq ) followed by differential gene expression (DGE) analysis and functional enrichment were performed to examine transcriptomic responses.
Results and future prospects
A comparative analysis across species revealed shared molecular pathways : mitogen-activated protein kinase (MAPK) signaling pathway was enriched in all three species , and ErbB and FoxO signaling pathways were enriched in AS and RT. A set of common differentially expressed genes was also observed , including 36 that were upregulated in response to stress. Among the upregulated genes are several involved in key biological functions such as immunity , apoptosis, stress modulation and epithelial regeneration . These findings offer valuable insights into conserved stress response mechanisms . Ongoing research will incorporate proteomic analysis of skin mucus and miRNA profiling from water samples to provide a more comprehensive understanding of the underlying biological processes and to support the identification of potential biomarkers for use in minimally invasive biosensors.
Keywords
Aquaculture, Biomarkers, Skin, Transcriptomics, Welfare indicators
Acknowledgements
Work Co funded by UKRI and by the European Union’s Horizon Europe research and innovation programme (GA No 101084651 project IGNITION). T.B. received funds from FCT - Fundação para a Ciência e a Tecnologia through grant 2023.04651.BDANA.