Investigations into endocrine changes associated with photoperiod treatment to arrest or promote puberty in male Atlantic cod

Sexual maturation leads to significant loss of body weight during the spawning season, and farmed cod normally nature at two years of age, before reaching commercial size. Photoperiod treatment is the most efficient strategy to enhance growth and delay pu berty in cod. Continuous light treatment (LL) in indoor tanks from 15 months onwards delays puberty to at least 3 years of age. However, LL treatment is less effective when applied on sea cages and typically puberty is only delayed by 4 – 5 months. Furthe r development of effective treatments to delay maturation is hampered by a lack of knowledge on the regulatory mechanisms controlling puberty in cod. The current project will therefore use different LL treatments to study activation of components of the b rain-pituitary-gonad axis, where some treatments fully inhibit puberty, some partially delay the process, and some restore the process until full sexual maturation. The main objective with the project is to elucidate the mechanism by which photoperiod affects timing of maturation in male Atlantic cod, by monitoring secretion of gonad sex steroids, and gene expression of Steriodogenic acute regulatory protein, key enzymes, hormones and their receptors in cod at different developmental stages and after treatment with different photoperiod regimes.