Salmon and trout (salmonids) are important species for global seafood production and have great ecological and economic significance. Most aquaculture production of salmonids employs anadromous species that utilize both freshwater and saltwater environments.
Throughout their life salmon and trout undergo major physiological transformations to transition between hypotonic and hypertonic aquatic environments. Maturation and spawning is also associated with dramatic sexual dimorphic physical changes and systemic tissue degeneration. Coloration changes and loss of muscle quality are challenges for salmonid aquaculture, even in iteroparous species, like Atlantic salmon and rainbow trout, because it reduces market value of premature spawning fish.
We investigated the involvement of endocrine factors in Pink Salmon, Oncorhynchus gorbuscha; Rainbow Trout, Oncorhynchus mykiss; and Chinook Salmon, Oncorhynchus tshawytscha life history transitions using a combination of physiological analysis, CRISPR genome editing technology and whole transcriptome analysis. In adult Pink Salmon, the immune system appeared to be a key player in the degeneration of both somatic and reproductive tissues in the final stages of male maturation. Enhanced bone development was also important for the development of sexual dimorphic traits in these species, particularly in Pink Salmon for which the characteristic hump in spawning males is the partial result of increase bone growth. In larval fish, the loss of key endocrine pathways has important implications for the development of morphological traits and research is ongoing to understand the role of these pathways in the freshwater life stage. Our diverse findings shed light on several key aspects of salmonid biology which will add to the growing understanding of these important finfish species.