Genetic, environmental, and behavioural factors underlying differential growth and alternative reproductive tactics in Chinook salmon, Oncorhynchus tshawytscha.

Alternative reproductive tactics (ARTs) in salmonids are influenced by differential growth amongst individuals. In Chinook salmon, Oncorhynchus tshawytscha, males develop into large “hooknose” males and smaller, precocious “jacks.” The production of jacks is influenced by genetics, environment, and possibly behaviour (i.e., aggression). I examined genetic, environmental, and behavioural factors underlying ARTs in Chinook salmon. By using a full-factorial breeding design, I found that jacking rate was explained by negative maternal, 12% additive, and 0% non-additive effects. I found that dams originating from low performance genetic lines produced families with higher jacking rates. I found that both rearing environment and sire ART influenced growth and variation in growth of offspring, respectively, and that these factors affected the aggression of offspring, which ultimately impacted their feeding success. Together, these results have implications for future research in the field of ARTs as well as for applications within the aquaculture industry