Date of Award

Fall 2021

Publication Type

Thesis

Degree Name

M.Sc.

Department

Biological Sciences

First Advisor

O. Love

Second Advisor

D. Higgs

Third Advisor

C. Semeniuk

Keywords

Aquaculture, Probiotics, Triploid

Rights

info:eu-repo/semantics/openAccess

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Abstract

Triploid salmon – fish with three sets of chromosomes – are regularly used in aquaculture as they are functionally sterile and therefore avoid the decline in flesh quality associated with sexual maturation. However, triploid fish exhibit many immune, behavioural, and physiological drawbacks which reduce their condition and survival in aquaculture environments. My research examines the effects of probiotic treatment to promote behavioural and stress-related (termed ‘coping styles’) traits more suited for aquaculture environments in triploid fish with the ultimate goal of increasing fish yield. In this study, Chinook salmon (Oncorhynchus tshawytscha) crosses were developed in a 3x3 and 3x2 design, with each family’s eggs split so that one half remained diploid (2N) and the other underwent triploidization (3N). At the alevin (exogenously feeding) stage, fish were reared under four treatment groups: 2N probiotic or regular feed, and 3N probiotic or regular feed. Juveniles were tested eight months postfertilization and individually assayed for behaviours to test for activity, exploration, predator responsiveness, and sociality. Fish were then terminally sampled for plasma cortisol concentrations as a measure of stress-induced response to aquaculture stressors. Subsets of fish were also sampled for baseline cortisol, as a measure of energetic demand, and for maximum cortisol, as an acute cortisol response. Triploid individuals exhibited marginally increased activity and neophobia, and showed reduced baseline, maximum, and behavioural stress-induced cortisol concentrations. Probiotics had an effect in increasing boldness and exploration behaviours, as well as reducing maximum cortisol concentrations. We also observed independent ploidy, behavioural, and physiological effects on mass, and interactive effects between behaviour and physiology, and physiology and feed on mass as well. Findings from this study may contribute to increasing yield in finfish aquaculture production by increasingbeneficial behaviours and reduce stressor responsiveness, thereby resulting in increased growth.

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