Research Document - 2013/045
Recovery Potential Modelling of Plains Minnow (Hybognathus placitus) in Canada
By J.A.M. Young and M.A. Koops
Abstract
The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has assessed the Plains Minnow (Hybognathus placitus) as Threatened in Canada (COSEWIC 2012). Here we present population modelling to assess population sensitivity, determine population-based recovery targets, and conduct simulations to estimate the impact of transient (one-time) harm in support of a recovery potential assessment (RPA). Our analyses demonstrated that the dynamics of a growing Plains Minnow population are most sensitive to perturbations that affect the survival of immature individuals. If post-spawning mortality is high, dynamics are also very sensitive to the fecundity of first-time spawners. A stable population, or one experiencing a year of low flow, is equally sensitive to survival of young-of-the-year (YOY) and young adults, and is more sensitive to the fecundity of age 2+ adults than a growing population. Harm to these portions of the life cycle should be minimized to avoid jeopardizing the survival and future recovery of Canadian Plains Minnow. Based on an objective of demographic sustainability (i.e., a self-sustaining population over the long term), and a 15% probability of catastrophic decline per generation, we propose a population abundance recovery target of approximately 60,600 adult Plains Minnow (ages 1+). This abundance requires, at minimum, 12 ha of suitable habitat including >115 km of barrier-free river for development of drifting eggs. Current available habitat in Canada is approximately 12.1 ha supporting 2,400–55,400 adults (COSEWIC 2012). At these abundances, the current risk of extirpation of a stable population is 2% (range 1–69%) over the next 100 years. However, current population trajectories are unknown. Therefore allowable transient harm should not exceed a 12.5% reduction in adult abundance, or a 17% reduction in YOY abundance, or a 7.5% reduction in total abundance within a 7 year period (approximately three generations).
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