Science Advisory Report 2019/051

Recovery Potential Assessment – River Darter, Percina shumardi (Great Lakes-Upper St. Lawrence populations)

Summary

• The current distribution of the Great Lakes-Upper St. Lawrence population of River Darter is limited to the Lake St. Clair watershed (Figure 1). Since 2005, River Darter have been collected from the Sydenham River, Thames River, and Lake St. Clair. Distribution in DU 3 appears to be decreasing.
• River Darter are typically collected in medium to large rivers or nearshore areas of lakes. They generally occur in deeper, moderate-velocity water over a variety of substrates, and are known to tolerate turbid waters. Little is known about spawning and feeding habitat but clean gravel and cobble substrates may be important features. Specific habitat information for River Darter in DU 3 is limited.
• The trajectory for abundance cannot be evaluated for DU 3 other than that River Darter continue to be rare.
• Recovery targets based on the minimum viable population (MVP) in the range of 27,000 to 31,000 are recommended. These estimates assume density-dependence with a maximum population growth rate of 2.49, a catastrophe frequency of 15% per generation, and a 1% extinction probability. MVP estimates were highly sensitive to simulation criteria, ranging from 3,700 to > 220,000.
• A population with an initial density of 10% of MVP would require between 33–35 years to reach recovery targets assuming the same simulation criteria and MVP analysis.
• An MVP sized population would require between 10.6 and 12.1 ha (1 ha = 10,000 m²) of habitat based on an Ordinary Least Squares (OLS) regression analysis of DU 1 and 2 River Darter densities assuming a 5% catchability (0.25 fish/m² density).
• In DU 3, the greatest threats to the survival and persistence of River Darter are exotic/invasive species (Round Goby), dredging, and sediment loading. Secondary threats include nutrient loading and contaminants and toxic substances. The potential impacts of Zebra Mussels and shoreline hardening are unknown.
• River Darter population dynamics are particularly sensitive to perturbations affecting young-of-year (YOY) survival rates and fertility. Harm to these aspects of life history should be avoided. Decreases in YOY-survival or fertility greater than 31–34% may result in population decline. Populations with an initial population growth rate of 1.32 may experience declines if anthropogenic harm (i.e., mortality) exceeds 24.5% for all age-classes or if YOY survival or reproductive success is reduced by 31–34%. Relationships between anthropogenic activities and changes in vital rates have not yet been established and require further research.
• There remain numerous sources of uncertainty related to DU 3 River Darter biology, ecology, life history, habitat requirements, population abundance, population structure, vital rates, and distribution. A thorough understanding of the threats affecting the decline of River Darter in DU 3 is also lacking.

This Science Advisory Report is from the January 31, 2019 Recovery Potential Assessment – River Darter, Percina shumardi, Great Lakes-Upper St. Lawrence Populations (Designatable Unit 3). Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Complete document (PDF, 910 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.