Scientific advice on the design of a comprehensive long-term monitoring program for redside dace (Clinostomus elongatus) to inform recovery and management decisions

Abstract

Redside Dace, a species listed as Endangered under the Species at Risk Act, has experienced severe declines throughout its Canadian range over the past 30 years. Federal and provincial recovery strategies indicate that the development of a long-term monitoring program to inform recovery and management decisions is a high priority recovery action. Distribution- and abundance-based indicators should be chosen to allow Redside Dace to be assessed relative to management objectives. Failure to clearly specify monitoring program objectives can lead to poor study design and an inability to understand the conservation status of the species or the influence of threats and recovery measures. The ability to detect changes through time is contingent on the application of a standardized monitoring approach. Monitoring design can include several spatial scales (site-level, sub-watershed, population, Canadian range). The choice of sampling scale is dependent on management objectives. Measuring the distribution and abundance of Redside Dace can be biased by imperfect detection, which is the failure to detect the species despite its occurrence. Field sampling design based on repeated surveys, and related modelling approaches, exist to account for imperfect detection. Addressing imperfect detection will improve upon previous guidance for monitoring Redside Dace. The ability to detect changes in distribution (occupancy) or trends through time is contingent on sampling efficiency, the occurrence of the species, the number of sampling sites, and the frequency of sampling. Many sites are required to detect small changes in occupancy; whereas, fewer sites are needed to detect large changes. Improved sampling efficiency will reduce effort requirements. Greater confidence in monitoring results will require increased sampling effort. Several gears exist to detect Redside Dace. Improvements to sampling design advice will require further evaluation of detection probability and harm imposed by each gear.