Abstract
The pesticide 3-trifluoromethyl-4-nitrophenol (TFM) is applied to rivers and streams draining into the Laurentian Great Lakes to control populations of invasive sea lamprey (Petromyzon marinus), which are ongoing threats to fisheries during the lamprey’s hematophagous, parasitic juvenile life stage. While TFM targets larval sea lamprey during treatments, threatened populations of juvenile lake sturgeon (Acipenser fulvescens), particularly young-of-the-year (<100 mm in length), may be adversely affected by TFM when their habitats overlap with larval sea lamprey. Exposure to TFM causes marked reductions in tissue glycogen and high energy phosphagens in lamprey and rainbow trout (Oncorhynchus mykiss) by interfering with oxidative ATP production in the mitochondria. To test that environmentally relevant concentrations of TFM would similarly affect juvenile lake sturgeon, we exposed them to the larval sea lamprey minimum lethal concentration (9-h LC99.9), which mimicked concentrations of a typical lampricide application and quantified energy stores and metabolites in the carcass, liver and brain. Exposure to TFM reduced brain ATP, PCr and glycogen by 50–60%, while lactate increased by 45–50% at 6 and 9 h. A rapid and sustained depletion of liver glucose and glycogen of more than 50% was also observed, whereas the respective concentrations of ATP and glycogen were reduced by 60% and 80% after 9 h, along with higher lactate and a slight metabolic acidosis (~0.1 pH unit). We conclude that exposure to environmentally relevant concentrations of TFM causes metabolic disturbances in lake sturgeon that can lead to impaired physiological performance and, in some cases, mortality. Our observations support practices such as delaying TFM treatments to late summer/fall or using alternative TFM application strategies to mitigate non-target effects in waters where lake sturgeon are present. These actions would help to conserve this historically and culturally significant species in the Great Lakes.
Highlights
In the early 20th century, parasitic sea lamprey (Petromyzon marinus) invaded the Laurentian Great Lakes, contributing to the devastation of commercial, recreational and culturally important fisheries, along with negative economic impacts on the communities that relied on the lakes and fishery for their livelihoods (Smith and Tibbles, 1980; Great Lakes Fisheries Commission (GLFC), 2011)
TFM is applied at 1.2–1.5 times the sea lamprey minimum lethal concentration (MLC) in order to account for dispersal and dilution of TFM and to maintain the appropriate target concentration as the lampricide block moves down the river
Brain glucose concentrations were unchanged in the presence of TFM (Fig. 2A) but glycogen was significantly depleted by 50% at 6 and 9 h relative to the control fish (Fig. 2B)
Summary
In the early 20th century, parasitic sea lamprey (Petromyzon marinus) invaded the Laurentian Great Lakes, contributing to the devastation of commercial, recreational and culturally important fisheries, along with negative economic impacts on the communities that relied on the lakes and fishery for their livelihoods (Smith and Tibbles, 1980; GLFC, 2011) In response to this ecological and economic emergency, the Great Lakes Fisheries Commission (GLFC) was formed in mid 1950s by the Canadian and US governments, with a mandate to develop a comprehensive program to eliminate/control invasive sea lamprey populations in the Great Lakes basin (GLFC, 2011). When treating longer rivers (e.g. several kilometres), or in rivers with large water discharges, it is necessary to have additional application stations along lower parts of the river to boost the concentration of TFM (Smith and Tibbles, 1980; Bills et al, 2003; Boogaard et al, 2003; McDonald and Kolar, 2007)
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