Fish carcass deposition to suppress invasive lake trout through hypoxia causes limited, non‐target effects on benthic invertebrates in Yellowstone Lake

Abstract

Invasive species can have negative effects on native biodiversity and ecosystem function, and suppression is often required to minimize the effects. However, management actions to suppress invasive species may cause negative, unintended effects on non‐target taxa. Across the United States, lake trout (Salvelinus namaycush) are invasive in many freshwater ecosystems, reducing native fish abundance and diversity through predation and competition. In an integrated pest management approach, lake trout embryos in Yellowstone Lake, Wyoming, are suppressed by depositing lake trout carcasses onto spawning sites; the carcasses reduce dissolved oxygen concentrations as they decay, causing embryo mortality. We conducted a field experiment during one ice‐free season at four sites in Yellowstone Lake to investigate the non‐target effects of carcass treatment on benthic invertebrates, which could have consequences for native fish diets. While overall invertebrate density and biomass did not respond to carcass treatment, Chironomidae midges and Sphaeriidae fingernail clams decreased in abundance. Carcass treatment altered invertebrate community structure based on density, but not biomass. Carcass treatment to suppress invasive fish embryos has spatially localized, non‐target effects on some benthic invertebrate taxa. Given the small spatial extent of carcass treatment within the lake, we conclude it is unlikely that carcass treatment will alter food availability for native fishes.

Aerial Application of Organic Pellets Eliminates Lake Trout Recruitment from a Primary Spawning Reef in Yellowstone Lake

“…Nevertheless, adverse ecosystem-scale effects are unlikely (Siemiantkowski et al 2022) because the total surface area of all 14 known spawning reefs (11.4 ha) represents only 0.03% of the surface area of Yellowstone Lake (Koel et al 2020c) and pellets are applied in autumn, thus providing sufficient time for decomposition and dispersal before the growing season. Accordingly, only limited short-term ecological effects were detected after treatments with organic material (Lujan 2020;Briggs et al 2022). However, if pellet treatments are implemented at a larger scale in the future, monitoring will assess nutrient dynamics and whole-lake metabolism to guide management practices if unintended effects are detected.…”

“…Accordingly, only limited short‐term ecological effects were detected after treatments with organic material (Lujan 2020; Briggs et al. 2022). However, if pellet treatments are implemented at a larger scale in the future, monitoring will assess nutrient dynamics and whole‐lake metabolism to guide management practices if unintended effects are detected.…”