Gene transcriptional profiling to assess Chinook salmon osmoregulatory resilience to salinity challenges

Recent environmental shifts have posed significant threats to Pacific salmonids, however, genomic tools offer a means to evaluate their resilience against ongoing ecological changes. Moreover, as concerns for conservation and animal welfare intensify, non-invasive tissue sampling for evaluating wild species' physiological state is gaining traction.

Nonetheless, limited research has compared the gene expression profiles of fish obtained through non-lethal and lethal sampling methods. In this study, researchers performed a comparative gene transcriptional profiling analysis using 28 quantitative PCR assays on an OpenArray platform, serving as a osmoregulatory stress transcriptional profiling chip.

Fish samples were collected from Chinook salmon (Oncorhynchus tshawytscha) smolts exposed to freshwater (0 PSU), brackish water (15 PSU) or seawater (30 PSU) for 0 h, 24 h, and 72 h. The results indicated that most assays demonstrated higher qPCR amplification success in non-lethal gill biopsies and lethal gill tissues in comparison to other tissues.

Furthermore, the study discovered a greater number of significant differences in transcript abundance in traditional lethal tissues as opposed to non-lethal tissues. As the duration of salinity exposure increased, the gene transcript levels were generally upregulated in seawater samples as compared to freshwater samples for both non-lethal and lethal tissues.

Notably, the targeted genes for both non-lethal and lethal tissues showed a significant and positive correlation across time points. The findings of this research highlight the potential benefits of utilizing non-lethal tissue sampling methods to enhance Chinook salmon hatchery management, aid in determining optimal hatchery release times, and support future field applications aimed at safeguarding wild salmon populations.