A 40+ year programme to monitor brown trout, Salmo trutta L. (populations at 25 groundwater‐fed stream sites in southeast Minnesota, USA, was initiated to identify population trends, evaluate management actions and test ecological theories regulating populations. Significant increases between 1970 and 2018 were found for total biomass (an average of 5% annually) and abundance of juveniles (7%), all adults (7%) and adults ≥305...

We describe risk‐based viable population monitoring, in which the monitoring indicator is a yearly prediction of the probability that, within a given timeframe, the population abundance will decline below a prespecified level. Common abundance‐based monitoring strategies usually have low power to detect declines in threatened and endangered species and are largely reactive to declines. Comparisons of the population's estimated...