Research Document 2019/034

Recovery Potential Modelling of Redside Dace (Clinostomus elongatus) in Canada

By van de Lee, A.S., Poesch, M.S., Drake, D.A.R., et Koops, M.A.

Abstract

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has assessed Redside Dace (Clinostomus elongatus) as Endangered in Canada. Here a population model is presented to determine population-based recovery targets, assess allowable harm, and conduct long-term projections of population recovery in support of a recovery potential assessment (RPA). The analyses demonstrate that the dynamics of Redside Dace populations are particularly sensitive to perturbations that affect survival of immature individuals (from hatch to age-2) and population-level fecundity. Harm to these portions of the life cycle should be minimized to avoid jeopardizing the survival and future recovery of Canadian populations. Meta-population structure was incorporated into analyses. The manner in which catastrophes impacted segments of the meta-population influenced recovery target estimates, indicating that understanding the extent of meta-population structure throughout the species range is needed to refine recovery targets. To achieve demographic sustainability, (i.e., a self-sustaining population over the long term) under conditions with a catastrophe probability of 0.15/generation and a quasi-extinction threshold of 50 adults at a 1% probability of extinction over 100 years, population sizes ranging from 18,000 to 75,000 were required. This required between 3.2 and 13.2 ha of suitable Redside Dace habitat. Three recovery effort strategies were simulated that focused on improving vital rates (survival and fecundity). A declining population (λ = 0.89) required considerable improvement to individual vital rates (> 40%) to cease population decline. If, however, survival of all age-classes could be augmented simultaneously an improvement of only 13% was required. Depending on the strategy employed, recovery occurred after 48 to 120 years. Recovery efforts affecting survival of all age-classes provided the greatest improvement to population growth rate and therefore resulted in quickest recovery (48 years).