Science Advisory Report 2021/012

Recovery Potential Assessment of Pygmy Whitefish (Prosopium coulterii), Great Lakes – Upper St. Lawrence populations (DU5)

Summary

• Pygmy Whitefish DU5 individuals are found only in Lake Superior (Figure 1), where they occupy nearshore areas at depths ranging from ~50–110 m. Peak biomass occurs at 80–95 m trawl depths.
• Biomass of Pygmy Whitefish followed periodic fluctuations since 1989 but has declined since 2013 or approximately one generation. The Pygmy Whitefish biomass in 2018 was estimated to be 68,707 kg (CI: 2,465–1,357,612).
• The minimum viable population (MVP) size for Pygmy Whitefish in Lake Superior was determined to be approximately 4,000 adult females or 75 kg age-1+ biomass assuming a 99% likelihood of persistence over 100 years with a 15% catastrophe rate per generation. The minimum area required to support this population (i.e., minimum area for population viability [MAPV]) is approximately 21 km², which indicates that a large number of MVP-sized aggregations of the species may exist in Lake Superior.
• Population modelling demonstrated that Pygmy Whitefish populations were most sensitive to perturbations in juvenile survival.
• Threats to Pygmy Whitefish include climate change, invasive species and pollution; however, the impact of these threats is currently unknown. Predation from top predators such as Lake Trout (Salvelinus namaycush) and Burbot (Lota lota) may be limiting population growth.
• For DU5 individuals, knowledge gaps exist pertaining to reproductive ecology, habitat use by immature life stages, dispersal and genetic exchange, and factors that influence population dynamics including recruitment.

This Science Advisory Report is from the December 10th, 2019 peer review on Recovery Potential Assessment –Pygmy Whitefish (Prosopium coulterii), Great Lakes – Upper St. Lawrence populations (DU5). Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Science Advisory Report 2021/012 (PDF, 983 KB)

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