Research Document - 2012/131

Recovery Potential Modelling of Silver Shiner (Notropis photogenis) 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 Silver Shiner as Threatened in Canada (COSEWIC 2010). Here we present population modelling to assess population sensitivity, determine population-based recovery targets, and conduct long-term projections to estimate risk of extirpation in support of a recovery potential assessment (RPA). Models represent four Canadian populations: Grand River, Thames River, Bronte Creek, and Sixteen Mile Creek. Two model variations, representing competing hypotheses regarding the lifespan of Silver Shiner: short-lived (3 years) and long-lived (>10 years) were compared. Our analyses demonstrated that the dynamics of Silver Shiner populations are very sensitive to perturbations that affect the survival of immature individuals or the fertility of first time spawners, especially for the short-lived model. Harm to these portions of the life cycle should be minimized to avoid jeopardizing the survival and future recovery of Canada’s populations. Based on an objective of demographic sustainability (i.e., a self-sustaining population over the long term), we propose population abundance recovery targets of ~780,000 adult Silver Shiner (ages 1-3) in the case of the short-lived model, or ~700 adults (ages 3-10+) in the case of the long-lived model. These abundances require, at minimum, 0.87 km² or 0.07 km² for the short- or long-lived model respectively. Current estimated population abundances for all four Canadian populations exceed the long-lived targets, but only the Grand River population exceeds the short-lived target. At current densities and given current estimated available habitat, a short-lived Bronte Creek population is at greatest risk of extirpation in the next 100 years, with risk ranging from 5%-100% risk depending on frequency of catastrophic events. Risk to the Sixteen Mile Creek and Thames River populations ranges from 0%-33%. Both long- and short-lived models estimate that Silver Shiner populations are currently growing, but these estimated growth rates are very uncertain.

Complete document (PDF, 449 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.