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Photoperiod and Growth Manipulation Reduces the Problem of Unwanted Sexual Maturation in Arctic Charr, Salvelinus alpinus

dc.contributor.authorLiu, Qi
dc.contributor.copyright-releaseNoen_US
dc.contributor.degreeDoctor of Philosophyen_US
dc.contributor.departmentDepartment of Biologyen_US
dc.contributor.ethics-approvalReceiveden_US
dc.contributor.external-examinerDr. Tillmann Benfeyen_US
dc.contributor.graduate-coordinatorDr. Sophia Stoneen_US
dc.contributor.manuscriptsYesen_US
dc.contributor.thesis-readerDr. Tony Manningen_US
dc.contributor.thesis-readerDr. Christophe Herbingeren_US
dc.contributor.thesis-readerDr. Leslie MacLarenen_US
dc.contributor.thesis-supervisorDr. James Dustonen_US
dc.date.accessioned2019-11-20T13:44:52Z
dc.date.available2019-11-20T13:44:52Z
dc.date.defence2019-10-07
dc.date.issued2019-11-20T13:44:52Z
dc.description.abstractFarming diploid Arctic charr (Salvelinus alpinus; Labrador strain) in Atlantic Canada is greatly impeded by unwanted sexual maturation and associated loss of growth and meat quality. Up to 70% of fish in both sexes mature at age 2, due to accelerated growth from both a high energy diet and rearing in ‘warm’ 10°C well water. The goal to reduce maturity to <20% was achieved by manipulating photoperiod, rearing temperature and feeding in a series of five lab-based trials each lasting 12-18 months ending age 2. To explore the relationship between somatic growth and the physiological decision to mature, all fish were identified with a PIT-tag and measured monthly. Continuous light (LL) overwinter effectively reduced maturation. Histological analysis of germ cells revealed the change between natural daylength (LDN) and LL induced a dichotomous response, stimulating some fish and inhibiting others, dependent on the direction and timing of photoperiod change. Food deprivation and/or 5°C overwinter alone were less effective than LL at reducing maturation, but combining all three factors reduced maturity to <5%. Paradoxically, body weight, condition factor and lipid content were poor indicators of whether an individual would mature or not. Plasma melatonin monitoring indicated 50 lux at night was a sufficient intensity for effective LL treatment. Charr failed to exhibit a circannual rhythm of sexual maturation under LL and LD 8:16 suggesting the conventional thinking on the mechanism by which photoperiod controls sexual maturation among salmonids requires further investigation.en_US
dc.identifier.urihttp://hdl.handle.net/10222/76636
dc.language.isoenen_US
dc.subjectAge at Maturityen_US
dc.subjectSalmoniden_US
dc.titlePhotoperiod and Growth Manipulation Reduces the Problem of Unwanted Sexual Maturation in Arctic Charr, Salvelinus alpinusen_US

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