Science Advisory Report 2021/016

Science Advice on the Potential Harm of granular Bayluscide Applications to Fish and Mussel Species at Risk

Summary

• Granular Bayluscide (gB), a chemical lampricide, is applied in certain areas of the Great Lakes basin to assess and control Sea Lamprey (Petromyzon marinus) populations. Applications of gB have occurred since 1966 and are part of bi-national efforts to control the species, coordinated by the Great Lakes Fishery Commission and led by Fisheries and Oceans Canada and the U.S. Fish and Wildlife Service.
• The request for science advice resulted from gB applications in areas inhabited by fishes and mussels listed as Endangered, Threatened, or Special Concern under Canada’s Species at Risk Act (SARA), raising questions about the ecological effects of the lampricide on fishes and mussels of conservation concern.
• Fishes and mussels exposed to gB in the aquatic environment may experience sub-lethal or lethal effects due to the toxicity of the chemical including changes in growth, movement, reproduction, or survival. Bayluscide may also lead to changes in ecosystem components (prey, competitors, predators, host species) resulting in indirect effects.
• A risk assessment was undertaken to determine the relative risk of direct mortality stemming from gB applications on 24 fishes (21 with SARA status) and 15 mussels (all with SARA status) in the Canadian waters of the Great Lakes basin. A modelling study was conducted to understand potential mortality from a typical gB application cycle and the population consequences of repeated applications, focusing on applications in the Huron-Erie corridor and nearby tributaries.
• Between 2011 and 2017, gB applications (Figure 1) occurred within the distribution of 21 fish and all 15 mussel species of conservation concern, including areas that contain or previously contained critical habitat for six SARA-listed fishes and 10 SARA-listed mussels. Granular Bayluscide exposure is relevant for up to 27% of a species’ range and for less than 30% of gB application sites.
• For fishes, the relative risk of direct mortality was greatest for Silver Lamprey (Ichthyomyzon unicuspis), followed by Northern Brook Lamprey (Ichthyomyzon fossor), Lake Sturgeon (Acipenser fulvescens), and Northern Madtom (Noturus stigmosus). Relative risk for mussels was greatest for Salamander Mussel (Simpsonaias ambigua), Threehorn Wartyback (Obliquaria reflexa), and Hickorynut (Obovaria olivaria). Relative risk was based on historical patterns of gB applications. Deviations from historical application patterns will change the interpretation of relative risk.
• Modelling indicated that many fish and mussel species of conservation concern can experience direct mortality from gB applications due to their occurrence within application sites and the assumed toxic effects of the compound. Although the likelihood of mortality is generally low, mortality on the order of one to tens of non-target fishes and potentially hundreds of native lampreys and mussels can occur. Repeated applications of gB can lead to population consequences for certain fish species.
• Changes to the size, number, and frequency of gB applications has model-based support to reduce mortality imposed by gB. Other mitigation measures exist, such as reducing target concentrations of gB, applying gB to areas outside of critical habitat, and seasonal application of gB outside of reproductive periods. Mitigation measures, if pursued, should be empirically tested to ensure intended benefits for species of conservation concern are realized.

This Science Advisory Report is from the February 28–March 1, 2019 regional peer review meeting on Information on the Potential Harm to Fish and Mussel Species at Risk (SAR) from Bayluscide Applications. 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 2021/016 (PDF, 1,579 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.