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Impacts of pulsed applications of the aquatic herbicide diquat bromide on fish


Aquatic herbicides are a group of pesticides used to control aquatic weeds and invasive plants in surface waters. Diquat bromide is a registered pesticide that is commonly used in agriculture (e.g. potato, beans, and seed crops), but also in controlling aquatic submerged and floating weeds. The recommended timing of the pesticide application is once weeds are visible and in an active stage of growth, which can coincide with important spawning and early life-stage growth and development in fish.

Although previous studies have demonstrated the slight to moderate acute toxicity of diquat bromide in rainbow trout and fathead minnows, few studies have thoroughly examined the longer term effects of multiple pulse exposures that reflect these prescribed repeat applications. Particularly, the sub-lethal effects that diquat bromide has on growth, development, reproduction, behaviour and herbicide uptake into fish are poorly understood under these environmentally realistic pulse exposure scenarios.

The objective of this research is to thoroughly characterize the adverse effects of this aquatic herbicide on two fish species (rainbow trout and fathead minnow) during multiple stages of development, following pulse exposures that reflect current-use application rates. Whole organism (i.e. growth, development) and cellular (i.e. protein expression changes) level effects will be measured.

This research will generate new empirical data that directly addresses how an aquatic herbicide affects fish survival, growth and development. This research will also aid in the development of risk assessment plans for managing invasive plant species while mitigating effects on non-target aquatic wildlife.

Program Name

National Contaminants Advisory Group (NCAG)


2015 - 2017



Principal Investigator(s)

Vicki Marlatt
Assistant Professor, Department of Biological Sciences, Simon Fraser University (British Columbia)

Team Member(s)

Chris Martyniuk, Adjunct Professor, University of New Brunswick and Associate Professor, University of Florida, Center for Environmental and Human Toxicology (Florida)

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