Yellowstone Lake Ecosystem Restoration: A Case Study for Invasive Fish Management

Abstract

Invasive predatory lake trout Salvelinus namaycush were discovered in Yellowstone Lake in 1994 and caused a precipitous decrease in abundance of native Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri. Suppression efforts (primarily gillnetting) initiated in 1995 did not curtail lake trout population growth or lakewide expansion. An adaptive management strategy was developed in 2010 that specified desired conditions indicative of ecosystem recovery. Population modeling was used to estimate effects of suppression efforts on the lake trout and establish effort benchmarks to achieve negative population growth (λ < 1). Partnerships enhanced funding support, and a scientific review panel provided guidance to increase suppression gillnetting effort to >46,800 100-m net nights; this effort level was achieved in 2012 and led to a reduction in lake trout biomass. Total lake trout biomass declined from 432,017 kg in 2012 to 196,675 kg in 2019, primarily because of a 79% reduction in adults. Total abundance declined from 925,208 in 2012 to 673,983 in 2019 but was highly variable because of recruitment of age-2 fish. Overall, 3.35 million lake trout were killed by suppression efforts from 1995 to 2019. Cutthroat trout abundance remained below target levels, but relative condition increased, large individuals (> 400 mm) became more abundant, and individual weights doubled, probably because of reduced density. Continued actions to suppress lake trout will facilitate further recovery of the cutthroat trout population and integrity of the Yellowstone Lake ecosystem.

Geographic-Scale Harvest Program to Promote Invasivorism of Bigheaded Carps

“…Any such evaluation must consider that once a nuisance species becomes an economic resource or a part of local culture, it may no longer be considered a nuisance, but an asset. This could result in pressure to maintain the species or even expand its range to uninvaded regions [9,44], causing a paradox for managers trying to restrict or prevent the spread of certain invasives or mitigate their effects on native species and ecosystems (see Settle et al [45], and a related discussion on socioeconomic feedbacks of invasive lake trout control in Yellowstone Lake [3]). Given the large, geographical scale of this invasion and complicated harvest logistics, concerns about economic dependence on invasivorism that encourage stock enhancement are likely unmerited.…”

“…To accomplish the goals of the "fisher-side" commercial fishing strategy in the lower Illinois River, a stakeholders' meeting was held in Grafton, IL, in the period 20-21 September 2010, during which academic researchers, regulatory authorities, commercial fishers, fish processors, marketers, and distributors discussed using commercial harvest of bigheaded carp in the lower Illinois River as a means of augmenting contracted fishing occurring in the upper river (IISG 2010). Key findings that shaped the design of our removal experiment included the need to (1) improve safety and quality of harvested bigheaded carp as food, (2) properly brand and find markets for the product [29,32], (3) provide financial support for commercial fishers, (4) form a public-private partnership to stimulate harvest, and (5) use associated data to inform an adaptive management framework [36].…”

“…Invasive species threaten biodiversity worldwide [1], costing $120 billion USD annually in the United States [2]. Removal programs may control invasives [3]. For example, humans routinely overharvest fish stocks [4][5][6].…”

Benthic Suffocation of Invasive Lake Trout Embryos by Fish Carcasses and Sedimentation in Yellowstone Lake

“…Yellowstone National Park initiated a gillnetting suppression program in 1995 to minimize the effect of Lake Trout on Yellowstone Cutthroat Trout and the Yellowstone Lake ecosystem (Koel et al 2020a). Nevertheless, the Yellowstone Cutthroat Trout population in the lake declined precipitously (Syslo et al 2016).…”

“…As of November 2019, over 3.35 million Lake Trout had been removed from Yellowstone Lake by the gillnetting program. Yellowstone Cutthroat Trout have yet to reach primary desired conditions as outlined for Yellowstone National Park in the Native Fish Conservation Plan (Koel et al 2010) because of an expected lag in the gillnetting response (Koel et al 2020a). Accordingly, managers are seeking alternative forms of Lake Trout suppression to complement gillnetting and increase the efficiency of maintaining a suppressed population during the coming decades.…”