Adaptive photoperiod interpretation modulates phenological timing in Atlantic salmon.

Photoperiod, the portion of 24-h cycle during which an organism is exposed to illumination, is an important phenological cue in many animals. However, despite its influence on critical biological processes, there remain many unknowns regarding how variations in light intensity translate into perceived photoperiod. This experiment examined how light intensity variations affect perceived photoperiod in Atlantic salmon (Salmo salar) to determine whether photoperiod interpretation is, a) fixed such that anything above a minimum detection threshold is regarded as 'illumination', or b) adaptive and varies with recent light exposure.

The potential for cleaner fish-driven evolution in the salmon louse : Genetic or environmental control of pigmentation?

The parasitic salmon louse represents one of the biggest challenges to environmentally sustainable salmonid aquaculture across the globe. This species also displays a high evolutionary potential, as demonstrated by its rapid development of resistance to delousing chemicals. In response, farms now use a range of non-chemical delousing methods, including cleaner fish that eat lice from salmon.

Cyclic Hypoxia Exposure Accelerates the Progression of Amoebic Gill Disease.

Amoebic gill disease (AGD), caused by the amoeba , has led to considerable economic losses in every major Atlantic salmon producing country, and is increasing in frequency. The most serious infections occur during summer and autumn, when temperatures are high and poor dissolved oxygen (DO) conditions are most common. Here, we tested if exposure to cyclic hypoxia at DO saturations of 40-60% altered the course of infection with compared to normoxic controls maintained at ≥90% DO saturation.

Metabolic and functional impacts of hypoxia vary with size in Atlantic salmon.

The most capricious environmental variable in aquatic habitats, dissolved O, is fundamental to the fitness and survival of fish. Using swim tunnel respirometry we test how acute exposure to reduced O levels, similar to those commonly encountered by fish in crowded streams and on commercial aquaculture farms, affect metabolic rate and swimming performance in Atlantic salmon of three size classes: 0.2, 1.