Research Document 2021/034

Relative Risk of Granular Bayluscide Applications for Fishes and Mussels of Conservation Concern in the Great Lakes Basin

By Andrews, D.W., Smyth, E.R.B., Lebrun, D.E., Morris, T.J., McNichols-O’Rourke, K.A., and Drake, D.A.R.

Abstract

Bayluscide, a chemical lampricide, is used by government agencies in the Great Lakes basin to assess Sea Lamprey (Petromyzon marinus) as part of bi-national efforts to control the species. The use of granular Bayluscide has been highly successful in identifying and suppressing Sea Lamprey populations. However, the ecological risk of Bayluscide for fishes and mussels listed under Canada’s Species at Risk Act and other species of conservation concern is not well understood. This document: 1) identifies potential pathways (direct, indirect) and mechanisms (physiological, non-physiological) by which the application of granular Bayluscide may influence fishes and mussels of conservation concern; 2) evaluates the relative ecological risk of applications based on four metrics (spatial distribution, application intensity, habitat associations that predispose species to exposure, toxicity); 3) identifies mitigation measures that may reduce potential impacts to non-target species; and, 4) identifies uncertainties needed to refine risk estimates. Spatial analyses indicated that between 2011 and 2017, Bayluscide applications occurred within the distribution of 21 fish and 15 mussel species of conservation concern including areas identified as critical habitat for 16 species (6 fishes, 10 mussels). For fishes, relative risk was greatest for native lampreys (Silver Lamprey [Ichthyomyzon unicuspis] and Northern Brook Lamprey [Ichthyomyzon fossor]) followed by Lake Sturgeon (Acipenser fulvescens) and Northern Madtom (Noturus stigmosus). Native lampreys exhibited high relative risk given habitat preferences and the toxicity of Bayluscide to those species. Northern Madtom ranked highly due to exposure (spatial and temporal patterns of application) and toxicity. Lake Sturgeon ranked highly due to exposure, though results were not directly comparable with other species due to assessment methods. For mussels, relative risk was greatest for Salamander Mussel (Simpsonaias ambigua), Threehorn Wartyback (Obliquaria reflexa), and Hickorynut (Obovaria olivaria). Salamander Mussel and Threehorn Wartyback ranked highly due to exposure and toxicity. A high risk ranking for Hickorynut occurred due to exposure and habitat preference. Mitigation measures to reduce the ecological consequences of Bayluscide applications are numerous and include modifying the frequency and timing of treatments, decreasing the size of application sites, and avoiding areas near critical habitat. However, the effect of potential mitigation measures should be rigorously tested to ensure that desired outcomes for species of conservation concern are realized while avoiding unintended consequences. Lastly, as reduced control effectiveness of Sea Lamprey would have undesirable effects on species of conservation concern susceptible to parasitism by Sea Lamprey (e.g., Lake Sturgeon), optimization measures may be warranted to account for such trade-offs.

Research Document 2021/034 (PDF, 24,513 KB)

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