Mitigation of recurrent perturbation mortality is an important goal for river restoration and conservation of freshwater fish species

Abstract

Human perturbations affect many aquatic ecosystems globally. We use age-structured matrix population models to explore how population growth rates in short-lived freshwater fish are affected by recurrent environmental perturbations to river ecosystems. Simulations are summarized to reveal how species-specific fitness characteristics contribute to population sustainability in habitats subject to recurrent perturbation. Deterministic calculations are used to estimate time to population recovery with successive years of intermittence disturbance, followed by post-perturbation equilibrium conditions. Perturbation that reduces only juvenile survival has a shorter recovery time to initial population size and greater resilience of population growth than when adult survival is reduced. Consecutive occurrences of perturbation lengthen recovery time nonlinearly, more notably when adults experience perturbation mortality. We illustrate with an example how managers could identify multiple options to mitigate recurrent ecosystem perturbations by reducing perturbation frequency and/or mitigating perturbation mortality. Our simulations suggest parameter approximations for a hypothetical species provide a useful frame of reference for river restoration and conservation when life history data are lacking for a specific species of concern.

Effects of flow recession regime on stranding of Rio Grande silvery minnow suggests that conservation actions must overcome evolutionary traps

“…Rapid environmental changes frequently result in ecological or evolutionary traps. Robertson & Blumstein (2019) provide a framework to detect evolutionary traps and their effects on populations and identify management options for eliminating traps or Reale, 2020) as well as realized and simulated effects on the overall population (Walsworth & Budy, 2021;Hatch et al, 2022). Mitigation for evolutionary traps can be challenging and requires identifying the mechanism causing the trap and solutions to prevent maladaptive behaviour (Robertson & Blumstein, 2019).…”

“…Mitigation actions for conservation of the species should focus on restoring the mechanisms of disturbance resistance (the ability of a population to remain unchanged during disturbance) and resilience (the ability of a population to recover after a disturbance) to make progress towards recovery (Hatch et al, 2022).…”

“…Robertson & Blumstein (2019) provide a framework to detect evolutionary traps and their effects on populations and identify management options for eliminating traps or mitigating their impacts. The significance of flow recession on mortality of Rio Grande silvery minnow is well‐documented (Archdeacon, 2016; Archdeacon & Reale, 2020; Archdeacon, Diver & Reale, 2020) as well as realized and simulated effects on the overall population (Walsworth & Budy, 2021; Hatch et al, 2022). Mitigation for evolutionary traps can be challenging and requires identifying the mechanism causing the trap and solutions to prevent maladaptive behaviour (Robertson & Blumstein, 2019).…”

“…Maintaining high demographic resilience allows Rio Grande silvery minnow to increase quickly after population disturbances, as observed after severe drought in 2018 (Archdeacon et al, 2020). Mitigation actions for conservation of the species should focus on restoring the mechanisms of disturbance resistance (the ability of a population to remain unchanged during disturbance) and resilience (the ability of a population to recover after a disturbance) to make progress towards recovery (Hatch et al, 2022).…”

“…Flow intermittence and stranding can result in high mortality (Tramer, 1977; Vardakas et al, 2017). Mitigating the effects of flow intermittence on fishes is necessary for conservation of fish populations (Hatch et al, 2022). In turn, effective management actions will require understanding the mechanisms leading to fish stranding, including the response to intermittence at both the individual and population levels.…”