Uncertainties of population resilience and recovery: linking life histories to ecosystems

Understanding the resilience of populations to disturbance and their ability to recover following depletion is fundamental to both theoretical population biology and its applications to conservation biology and the development of sustainable harvesting strategies. Marine fisheries represent a major scale system of human-induced mortality in natural populations. Over the past decades, numerous commercially fished populations have declined to historically low levels and many show little signs of recovery despite large reductions in fishing pressure. The role of life-histories in fish population recovery ability and its demographic properties has gained considerable attention recently, as trends towards lower age and size at maturity and smaller body sizes have been documented in many commercially exploited fish populations. Changes in fish life histories can alter population growth rate directly, but they might also affect population recovery ability through ecosystem-level feedbacks, forming a major uncertainty component about any single-species based projections about population resilience and recovery ability. While population projections can be improved by more rigorous incorporation of key drivers and an ecosystem perspective, stochasticity is always present in nature, such that an outcome of the process of interest always remains to some extent random. The present proposal investigates the drivers and uncertainty of fish population resilience to and recovery from overfishing. To this end, I will project ecosystem feedbacks of life-history changes on population dynamics and estimate inherent uncertainty associated with fish population dynamics. To these ends, I will build fundamental life-history invariants into the Allometric Trophic Network modelling framework and analyze empirical time series on fish population dynamics in the context of Canadian fisheries. The proposed research aims to provide new insights into the factors that affect the rate and uncertainty of recovery in natural and human-harvested populations. This will be done by (i) accounting for both individual and ecosystem perspectives, (ii) quantifying the inherent uncertainty in recovery ability, and (iii) incorporating this uncertainty in rebuilding plans for depleted populations in a changing environment. The work has direct applicability to both natural and human-affected species, to their conservation and sustainable management.