Condition-dependent skipped spawning in anadromous brown trout (Salmo trutta)

Repeat spawners of anadromous salmonids may contribute significantly to population resilience by providing multiple cohorts to both seawater and freshwater life stages. In this study, winter survival of sea trout (Salmo trutta Linnaeus, 1758) post spawners (kelts) was 89%. Sea survival increased linearly with female length with a return probability between 30% and 50%, whereas males attained a maximum return probability of 60% at 520 mm. Of the returning sea trout, 40% skipped spawning and they had significantly lower condition factor as kelts compared with those who returned after one summer. These results suggest that sex-specific differences in individual post-spawning growth–survival t…

Common mechanisms for guidance efficiency of descending Atlantic salmon smolts in small and large hydroelectric power plants

Digital Data Help Explain Drivers of Angler Satisfaction : An Example from Southern Norway

We analyzed trip-level self-reports collected by a cell phone app to understand angler satisfaction of fishing for sea trout Salmo trutta (anadromous Brown Trout) in southern Norway. We found no clear support for a positive relationship between trip outcome (catch or no catch) and angler satisfaction level. In the cases where sea trout was caught, however, there was a positive relationship between fish size and angler satisfaction level. A total of 52% of the captured sea trout were voluntarily released, and releases were unrelated to fish size. In conclusion, digital data collected via a cell phone app are useful to reveal patterns of angler behavior and satisfaction. Paid open access

Effects of repeated short episodes of environmental acidification on Atlantic salmon (Salmo salar) from a landlocked population

Abstract Chronic or repeated exposure to environmental contaminants may result in allostatic overload, a physiological situation in which the costs of coping affect long-term survival and reproductive output. Continuous measurements in Otra, the largest river in southern Norway, show the occurrence of repeated 24–48 h episodes of acidification. This work investigates the impact of repeated short acidification episodes on a unique land-locked population of normally anadromous Atlantic salmon (“Bleke”). This was done by recording physiological measures of stress and allostatic load in fish exposed for 7 days to continuous or repeated episodes of simulated environmental acidification or untrea…

Migratory passage structures at hydropower plants as potential physiological and behavioural selective agents

Anthropogenic activities affect fish populations worldwide. River dams have profound impacts on ecosystems by changing habitats and hindering migration. In an effort to counteract such effects, a range of mitigation measures have been installed at hydroelectric power plants. However, not all individuals in a population use these measures, potentially creating strong selection processes at hydroelectric power plants. This may be especially true during migration; fish can get heavily delayed or pass through a hydropower turbine, thus facing increased mortality compared with those using a safe bypass route. In this study, we quantify migration route choices of descending wild passive integrate…

Neuroendocrine indicators of allostatic load reveal the impact of environmental acidification in fish

Abstract When mobilized from surrounding soils and binding to gills at moderately low pH, aluminum (Al) cations can adversely affect fish populations. Furthermore, acidification may lead to allostatic overload, a situation in which the costs of coping with chronic stress affects long-term survival and reproductive output and, ultimately, ecosystem health. The brain's serotonergic system plays a key role in neuroendocrine stress responses and allostatic processes. Here, we explored whether sublethal effects of Al in acidified water affects serotonergic neurochemistry and stress coping ability in a unique land-locked salmon population from Lake Bygelandsfjorden, in southern Norway. Fish were …