No abstract

The pace of life hypothesis (POLS) predicts that personality traits, like activity and boldness, are positively correlated with growth and metabolism. Here, we assess whether personality could predict body mass, metabolic rate, and performance under stress for hatchery raised Atlantic salmon (Salmo salar) 15 months post fertilization. Personality was evaluated for individual fish using a series of repeated trials alongside two stressful events (PIT tagging, simulated transport), to determine performance under stress. Standard metabolic rate (SMR) was then assessed via intermittent flow respirometry, and the relationships between personality, body mass, performance, and SMR were evaluated. Fish displayed repeatable behaviours, but not in accordance with POLS hypothesis. Smaller fish were more active and responsive to stimuli, while personality was not associated with SMR. Although smaller fish and fish with higher SMR both performed better under stress, body mass was unrelated to SMR. We discuss the utility of supporting the occurrence of a wider range of growth rates and body sizes in hatchery environments, as a means of promoting greater stress tolerance as well as faster growth.

Alternative reproductive tactics are widespread in fishes. In Pacific salmon, males either become a competitive hooknose, or a sneaker jack, which is undesirable in aquaculture when overabundant. Juveniles often experience accelerated growth prior to becoming jacks, potentially caused by increased competitiveness. We tested the behaviour of hatchery-reared Chinook salmon (Oncorhynchus tshawytscha), in fresh water and after one year in salt water. We also tested the effects of freshwater rearing density (100, 50 or 35 fish per 200 L), food ration (high or low), sire (jack or hooknose) for jacks, hooknoses, and females with and without confirmed jack siblings. Sisters of jacks were further identified to test whether females closely related to jacks also showed behavioural differences. Overall, jacks did not behave as predicted; rearing conditions were the strongest determinant of behaviour, and jack sisters behaved differently than jacks and other females. Our study underscores the complexities of jack behaviour, and of females closely related to jacks, at all development stages, and supports the use of behavioural screenings to regulate jacking rates in hatcheries by identifying jack sisters.