Context drives movement patterns in a mobile marine predator.

Intra-specific variability in movement behaviour occurs in all major taxonomic groups. Despite its common occurrence and ecological consequences, individual variability is often overlooked. As a result, there is a persistent gap in knowledge about drivers of intra-specific variability in movement and its role in fulfilling life history requirements.

Redefining the oceanic distribution of Atlantic salmon.

Determining the mechanisms driving range-wide reductions in Atlantic salmon marine survival is hindered by an insufficient understanding of their oceanic ecology and distribution. We attached 204 pop-up satellite archival tags to post-spawned salmon when they migrated to the ocean from seven European areas and maiden North American salmon captured at sea at West Greenland. Individuals migrated further north and east than previously reported and displayed increased diving activity near oceanographic fronts, emphasizing the importance of these regions as feeding areas.

Selection against individuals from genetic introgression of escaped farmed salmon in a natural population of Atlantic salmon.

The viability of wild Atlantic salmon populations is threatened by genetic introgression from escaped farmed salmon. Farmed Atlantic salmon are genetically improved for important commercial traits and a life in captivity but are poorly adapted to the natural environment. The rate of gene flow from escaped farmed to wild salmon depends on their spawning success and on offspring survival at various life stages.

Factors influencing return rate and marine residence duration in sea trout populations in Central Norway.

Brown trout (Salmo trutta) display extensive plasticity in marine migratory behaviours, with marine migrations considered to be an adaptive strategy which enables sea trout to maximize growth and reproductive potential. However, marine migrations are not without associated costs, including threats posed by ever-increasing salmon lice (Lepeophtheirus salmonis) infestations. In the present study, we used passive integrated transponder technology to characterize variability in sea trout migration behaviour amongst three catchments situated in a region of intensive salmon farming in central Norway.

Implications of the movement behaviour of African tigerfish Hydrocynus vittatus for the design of freshwater protected areas.

African tigerfish Hydrocynus vittatus (n = 35) were tagged with external radio-transmitters in the Kavango River, Namibia, to determine whether freshwater protected areas could be an effective tool for the management and conservation of this species. They were manually tracked in the core study area of 33 km every c. 12 days from July-October 2016 to May 2017 for between 123 to 246 days.

Gene flow from domesticated escapes alters the life history of wild Atlantic salmon.

Interbreeding between domesticated and wild animals occurs in several species. This gene flow has long been anticipated to induce genetic changes in life-history traits of wild populations, thereby influencing population dynamics and viability. Here, we show that individuals with high levels of introgression (domesticated ancestry) have altered age and size at maturation in 62 wild Atlantic salmon Salmo salar populations, including seven ancestral populations to breeding lines of the domesticated salmon.

Sex-dependent dominance at a single locus maintains variation in age at maturity in salmon.

Males and females share many traits that have a common genetic basis; however, selection on these traits often differs between the sexes, leading to sexual conflict. Under such sexual antagonism, theory predicts the evolution of genetic architectures that resolve this sexual conflict. Yet, despite intense theoretical and empirical interest, the specific loci underlying sexually antagonistic phenotypes have rarely been identified, limiting our understanding of how sexual conflict impacts genome evolution and the maintenance of genetic diversity.

Basin-scale phenology and effects of climate variability on global timing of initial seaward migration of Atlantic salmon (Salmo salar).

Migrations between different habitats are key events in the lives of many organisms. Such movements involve annually recurring travel over long distances usually triggered by seasonal changes in the environment. Often, the migration is associated with travel to or from reproduction areas to regions of growth.

Does boat traffic cause displacement of fish in estuaries?

Estuaries are increasingly under threat from a variety of human impacts. Recreational and commercial boat traffic in urban areas may represent a significant disturbance to fish populations and have particularly adverse effects in spatially restricted systems such as estuaries. We examined the effects of passing boats on the abundance of different sized fish within the main navigation channel of an estuary using high resolution sonar (DIDSON).

Using mass scaling of movement cost and resource encounter rate to predict animal body size-population density relationships.

The negative relationship between body mass and population abundance was documented decades ago and forms one of the most fundamental scaling-laws in ecology. However, current theory fails to capture observed variations and the subject continues to raise controversy. Here we unify empirically observed size-abundance relationships with theory, by incorporating allometries in resource encounter rate and metabolic costs of movements.

Adaptive winter survival strategies: defended energy levels in juvenile Atlantic salmon along a latitudinal gradient.

Current knowledge suggests that patterns of energy storage and depletion in animals are governed by behavioural trade-offs between risks associated with feeding and future energy demands. However, the length of adverse periods varies over geographical or climatic gradients. To explore the potential for genotypic sources of variation in behavioural trade-offs, we compared the winter energy-depletion patterns among 13 wild populations of juvenile Atlantic salmon (Salmo salar L.

Crossing invisible boundaries: the effectiveness of the Langebaan Lagoon marine protected area as a harvest refuge for a migratory fish species in South Africa.

The application of no-take areas in fisheries remains controversial. Critics argue that many targeted species are too mobile to benefit from area protection and that no-take areas are only appropriate for resident species. The degree of protection does not depend on the size of the no-take area but rather on the time fish reside inside its boundaries during key life-history events (i.