In‐Situ Evaluation of Benthic Suffocation Methods for Suppression of Invasive Lake Trout Embryos in Yellowstone Lake

Abstract

Suppression of invasive Lake Trout Salvelinus namaycush is an important management tool to use in native fish and ecosystem conservation throughout the U.S. Intermountain West. Lake Trout suppression, primarily by gill netting, has been ongoing in Yellowstone Lake, Yellowstone National Park, Wyoming, since 1995. Additional methods that cause mortality of Lake Trout embryos could be used simultaneously with gill netting to enhance suppression. Our objective was to evaluate the in‐situ efficacy of two benthic suffocation methods—tarping with gas‐impermeable tarps and Lake Trout carcass deposition to increase the mortality of Lake Trout embryos. Tarping did not increase embryo mortality; mean control mortality was 21 ± 1.9% (mean ± SE), and mean tarp‐treatment mortality was 20 ± 2.9%. Lake Trout carcass deposition caused 98 ± 1.2% mean mortality of embryos at the substrate surface and 100 ± 0.1% mean mortality of embryos 20 cm below the substrate surface. Hypoxic conditions in the carcass treatments were probably the cause of the high embryo mortality; dissolved oxygen concentrations at the substrate surface declined from 7.74 to 0.06 mg/L when carcasses remained on the treatment locations. The deposition of Lake Trout carcasses shows potential to be an additional suppression method that can induce mortality in Lake Trout embryos through benthic suffocation and could be implemented at Lake Trout spawning sites in Yellowstone Lake.

Targeting Aggregations of Telemetered Lake Trout to Increase Gillnetting Suppression Efficacy

“…; Williams ), which is a prerequisite when considering novel suppression methods, such as embryo suffocation (Thomas et al. ). The premise for using multiple suppression methods (e.g., gill netting and embryo suffocation) to increase suppression efficacy is founded in the integrated pest management approach (Ehler ).…”

“…Fish and Wildlife Service, personal communication). Tracking of adult Lake Trout during the spawning season is also used to identify spawning locations (e.g., Dux et al 2011;Fredenberg et al 2017;Williams 2019), which is a prerequisite when considering novel suppression methods, such as embryo suffocation (Thomas et al 2019). The premise for using multiple suppression methods (e.g., gill netting and embryo suffocation) to increase suppression efficacy is founded in the integrated pest management approach (Ehler 2006).…”

“…When suppression effort is limited, using the most efficient gear at the time when the target species is most vulnerable can increase suppression efficacy (Britton et al 2011). In many cases, resource managers try novel and creative removal strategies to increase the efficacy of invasive species suppression (Loppnow et al 2013;Bouska et al 2017;Thomas et al 2019).…”

Organic Pellet Decomposition Induces Mortality of Lake Trout Embryos in Yellowstone Lake

“…; Thomas et al. ), with an overall goal of increasing suppression efficiency while reducing long‐term costs.…”

“…Whole and ground Lake Trout carcasses caused 100% mortality of Lake Trout embryos at the substrate surface and at a depth of 20 cm in the substrate at treated spawning sites (Poole ; Thomas et al. ). Biological oxygen demand of the decomposing carcasses caused DO to decline to 0 mg/L soon after treatments and caused the high embryo mortality.…”