Research Document - 2013/029
Recovery potential modelling of Mountain Sucker (Catostomus platyrhynchus), Milk River populations
By J.A.M. Young and M.A. Koops
Abstract
The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has assessed the Milk River populations of Mountain Sucker (Catostomus platyrhynchus) as Threatened in Canada (COSEWIC 2010). Here we present population modelling to assess allowable harm, determine population-based recovery targets, and conduct long-term projections of population recovery in support of a recovery potential assessment (RPA). Our analyses demonstrated that the dynamics of Mountain Sucker populations are very sensitive to perturbations that affect the survival of immature individuals (from hatch to age 2), and to the collective survival of adults (ages 2-6). Harm to these portions of the life cycle should be minimized to avoid jeopardizing the survival and future recovery of Canada’s Milk River populations. Based on an objective of demographic sustainability (i.e., a self-sustaining population over the long term), we propose a population abundance recovery target of 6400 adult Mountain Sucker, requiring 3.0 – 16.6 ha of suitable habitat. Current estimates of mean vital rates suggest the population may be in decline, although parameter values are sufficiently uncertain that this may not be the case. Recovery strategies which incorporate improvements in the most sensitive vital rates of Mountain Sucker are most likely to improve the population growth rate; improvements of 20% in survival of all life stages significantly delayed extinction risks, and improvements of 84% and 28% respectively to juvenile and adult survival stimulated population growth.
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