Contrasting demographic responses to size‐selective harvesting among neighbouring wild fish populations

Sustainable harvesting of wild populations relies on evidence-based knowledge to predict outcomes for species and the ecosystems they inhabit. Although may elicit compensatory density-dependence, it is generally size-selective, which induces additional pressures that are challenging forecast. Furthermore, responses harvest be population-specific whether generalizable patterns exist remains unclear. Taking advantage Parks Canada's mandate remove introduced brook trout Salvelinus fontinalis restore alpine lakes in Canadian parks, we experimentally applied standardized size-selective rates (the largest ~64% annually) three consecutive summers five with different initial size structures. Four unharvested were used as controls. At reduced densities, harvested control exhibited similar density-dependent increases specific growth, juvenile survival earlier maturation. However, simultaneously induced changes age structure contrasted among populations. Average body length decreased populations, whereas tended increase over 3 years. We also detected contrasting, variability ultimately length- age-at-harvest but not Overall, smaller, more homogeneous sizes, living at high densities most resilient harvesting, exhibiting smallest change size-at-age. In contrast, large-bodied substantial size-structure following selective harvesting: experienced either stabilizing or disruptive pressures, when was low, respectively. Synthesis application. Our results show within species, inherently leads risk uncertainty larger varied sizes than smaller-bodied less range size. study supports prioritizing regulations protect sizes. Such a management strategy would reduce likelihood eliciting unpredictable undesirable demographic fish these attributes.