Littoral habitat loss caused by multiyear drought and the response of an endemic fish species in a deep desert lake

Abstract

Multiyear drought is projected to increase in frequency and duration in arid and semiarid regions across the world, threatening native species and ecosystem function. The effects of multiyear drought are often exacerbated by human water use for consumption, energy production, and agriculture, which, in lentic ecosystems, manifest in reduced lake elevation and altered habitat for aquatic species. Here, we demonstrate that decreasing lake levels, associated with drought and water management, reduce the availability of littoral cobble habitat to fishes by creating an elevation‐explicit littoral habitat map. We combined long‐term fish catch data and a lake elevation time series with our elevation‐explicit littoral habitat map to test whether fish species population demographics are related to drought‐driven changes in littoral habitat. We surveyed the littoral zone of Bear Lake, Utah and Idaho, U.S.A., from full pool to a depth of >12 m, totalling 94.86 km2 surveyed. As lake elevation decreased >6 m from full pool to the lowest historical elevation, the area of littoral cobble decreased by >97%. Bear Lake sculpin (Cottus extensus, Cottidae), a cold‐water fish species which relies on cobble for reproduction, catch per unit effort decreased by >75% with littoral cobble, and year class strength declined by as much as 86%, but varied across age. We predicted the response of age‐0 to age‐4 sculpin under high and low cobble availability. Our simulations predict a 60%–85% decline in juvenile sculpin CPUE (age‐2 and younger) when cobble availability decreases from the 95th to 5th percentile. Our study provided a unique opportunity to identify quantitative linkages between climate‐driven littoral habitat loss and an ecologically important profundal fish species, expanding our understanding of potential future pathways through which climate change may affect lentic ecosystems and fishes.

In Water‐Limited Landscapes, an Anthropocene Exchange: Trading Lakes for Irrigated Agriculture

“…As lakes shrink in size, their shorelines migrate offshore and their littoral zones are heavily impacted: they lose their macrophytic vegetation (Zohary & Ostrovsky, 2011) and their substrate becomes mainly smaller‐sized particles (Hofmann et al, 2008). These changes translate to loss of habitats of high structural complexity that are utilized by fish and invertebrates (Gasith & Gafny, 1990; Glassic & Gaeta, 2019). As a result, sensitive species disappear, with marked loss to biodiversity while a few generalist invasive species are advantaged (Zohary & Gasith, 2014).…”

The influence of multiyear drought and associated reduction in tributary connectivity on an adfluvial fish species

“…Additional metrics including changes in weight or condition factor may provide more information regarding the influence of drought on cutthroat growth than changes in total length, though an individual‐based analysis using these metrics would require a mark–recapture study or similar method. While shoreline habitat changes substantially as lake level declines (Glassic & Gaeta, ), very little lake volume is lost relative to lake‐level decline and littoral exposure. Adfluvial Bear Lake Bonneville Cutthroat Trout are pelagic during nonspawning periods (Nielson & Lentsch, ).…”

“…We mapped Bear Lake to 12.52 m below full pool elevation using terrestrial and aquatic habitat surveying techniques as further described in Glassic and Gaeta (). We combined real‐time kinematics (RTK) terrestrial surveys and hydroacoustic surveys to generate a 5 × 5 m digital elevation model.…”

Filamentous Algae Blooms in a Large, Clear-Water Lake: Potential Drivers and Reduced Benthic Primary Production

“…However, in 1911, the Bear River was linked to Bear Lake by damming the river, constructing a man-made channel for inflow to the lake, and constructing an additional outlet channel that was supplemented by a large, electric pump for outflow, allowing the Bear Lake basin to be used to store excess water and regulate its supply for downstream agriculture. More recently, research on Bear Lake has raised concerns that extreme water level drawdown in the lake may be imperiling some endemic fish species that rely upon littoral locations for spawning [29]. The primary community near Bear Lake is Garden City, UT, located on the western shore (population ~550 in 2019, with tourism populations surging to ~30,000 during summer months).…”

“…The results are expressed in the δ notation, using ratios of samples and isotope standards issued by the International Atomic Energy Agency (IAEA), on the Vienna Pee Dee Belemnite (V-PDB) for δ 13 C, and atmospheric nitrogen (air-N 2 ) scale for δ 15 N. The analytical error (mean SD from repeat measurements of in-house standards) for each run was always smaller than 0.3 ‰ for δ 13 C and δ 15 N. ever, in 1911, the Bear River was linked to Bear Lake by damming the river, constructing a man-made channel for inflow to the lake, and constructing an additional outlet channel that was supplemented by a large, electric pump for outflow, allowing the Bear Lake basin to be used to store excess water and regulate its supply for downstream agriculture. More recently, research on Bear Lake has raised concerns that extreme water level drawdown in the lake may be imperiling some endemic fish species that rely upon littoral locations for spawning [29]. The primary community near Bear Lake is Garden City, UT, located on the western shore (population ~550 in 2019, with tourism populations surging to ~30,000 during summer months).…”