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Development of a Melatonin Assay to Assess Effectiveness of Photoperiod Regimes Used to Reduce Grilsification



Photoperiod plays a significant role in the development and maturation of salmon. Alterations in the natural photoperiod can accelerate or decelerate smoltification or reproductive maturation. By appropriately manipulating photoperiod, spawning times can be controlled to allow for the production of out-of-season smolts, and grilse rates can be reduced during grow out allowing enhanced growth and greater insurance of quality marketable product.

The way in which photoperiod is perceived by salmon and how signals are relayed to systems which control sexual maturation is not clearly understood. It is thought, however that melatonin, produced by the pineal gland, is a significant mediator of the photoperiod effects. In salmon, melatonin levels rise during dark hours and drop during light hours. Since melatonin levels appear to help communicate day/night lengths to salmon, monitoring its levels would be an effective way to measure the efficiency and accuracy of artificial lighting systems in lengthening light hours in a 24 hour day.

The focus of this study is to investigate the levels of melatonin observed in salmon under natural lighting photoperiods in the Bay of Fundy region and under manipulated photoperiods through the use of artificial lighting. Melatonin levels will be correlated with grilse rates, fish weight, water temperatures, family/stock origin and light intensity measurements. This data should provide information on the effectiveness of the lighting regimes being used in reducing melatonin levels and give insight on how grilse rates might be further reduced.

Program Name

Aquaculture Collaborative Research and Development Program (ACRDP)


2007 - 2009


Atlantic: Gulf of Maine, Scotian Shelf

Principal Investigator(s)

Brian Glebe

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