Interactions Between Life History, Recovery, and Resilience in Fishes presented by Jeff Hutchings
Department of Biology, Dalhousie University
5th Floor Biology Lounge, Life Science Centre, Dalhousie University
Studies on small and declining populations dominate research in conservation biology. This emphasis reflects two overarching frameworks: the small-population paradigm focuses on correlates of increased extinction probability; the declining-population paradigm directs attention to the causes and consequences of depletion. Neither, however, particularly informs research on the determinants, rate, or uncertainty of population increase. In contrast, Allee effects (positive associations between population size and realized per capita population growth rate -- also a metric of average individual fitness) offer a theoretical and empirical basis for identifying numerical and temporal thresholds at which recovery is unlikely or uncertain.
Notwithstanding a literature permeated by confusion and conflation (of cause with pattern), most meta-analyses used to detect Allee effects (in fishes) have been fraught with data limitation at low abundance, low statistical power, and at least one questionable, but key, assumption. I adopt an alternative approach, examining the correlates of abundance trajectories observed for 19 marine fish populations deemed to have recovered from depletion and 16 that have not, despite threat mitigation. Comparing terrestrial and aquatic vertebrates, population-size thresholds for impaired recovery are likely to be comparatively lower for some taxonomic groups than others. A metric of natural mortality – articulated by simply measured parameters associated with body size and growth rate – appears to provide an empirically tractable and theoretically defensible correlate of recovery in fishes.Biology Seminar