Landscape topography and the distribution of Lahontan cutthroat trout (Oncorhynchus clarki henshawi) in a high desert stream

Abstract

Lahontan cutthroat trout, Oncorhynchus clarki henshawi, are currently limited in their distribution to a patchwork of small isolated populations, the result of habitat degradation and natural variation in landscape and in-stream conditions. The objectives of this study were to determine if landscape topography influences trout distribution, and if water temperatures control this response. The work was carried out in a sub-basin of the Quinn River system, McDermitt Creek, which drains the sagebrush desert of southeastern Oregon and northern Nevada. Headwater tributaries of this creek consist of alternating canyon-confined and valley bounded reaches. Trout within these systems are challenged by low discharge and high temperatures during the summer, and anchor ice during the winter. Contiguous whole stream surveys were used to look at trout distribution during the summer of 2003 and spring and fall of 2004. Our results suggested that topography can affect trout distribution. Trout numbers were highest in areas with greater numbers of nick-points (the transition zones between less confined and more confined valley segments) and greater valley confinement. Additionally, in the downstream portion of our headwater reaches, more trout were found in nickpoints than expected based on the availability of this habitat type. Our data suggest that hyporheic inputs may be high in such areas, thus providing trout with shelter from warm water in the summer, anchor ice in the winter, and shallow stream depths during all seasons. Spatial occurrence of these areas of refugia can be taken into consideration when planning land use activities and restoration efforts. Further research is required to confirm that topography can affect the distribution of Lahontan cutthroat trout in other systems, and to better understand the mechanisms behind these patterns.

Spatial distribution of thermal refuges analysed in relation to riverscape hydromorphology using airborne thermal infrared imagery

“…Conversely, refuge concentrations appear to be sparsest within either extremely confined, deeply incised valleys or within completely unconfined sections of river that flow through flat terrain, devoid of valley walls. These results agree with a range of other studies noting the presence of cold water upwelling within semi-confined river valley segments, generally referred to in the literature as 'bounded alluvial valleys' ('BAVs'; Baxter, Frissell, & Hauer, 1999;Baxter & Hauer, 2000;Benjamin, Dunham, & Dare, 2007;Boxall, Giannico, & Li, 2008;Fausch et al, 2002;Roberts, Fausch, Peterson, & Hooten, 2013;Stanford & Ward, 1993;Ward et al, 2002;Wright, Baxter, & Li, 2005). Cool upwelling in BAVs is generally attributed to impermeable rock protrusions ('knickpoints') at the downstream end of the valley segment which force subsurface flow to upwell from the water table or hyporheic zone (Baxter & Hauer, 2000;Brunke & Gonser, 1997;Harner & Stanford, 2003;Malard et al, 2002;Poole, Stanford, Frissell, & Running, 2002;Stanford & Ward, 1993).…”

Temperature‐Related Changes in Habitat Quality and Use by Bonneville Cutthroat Trout in Regulated and Unregulated River Segments

“…Cutthroat trout distributions were similar to the spatial arrangement of coolwater refuges in each study segment, suggesting thermal refuges during high water temperatures are important. Thermal refuges are a significant component to the survival and distribution of coldwater species living in environments that can experience extreme temperature even for short periods (Ebersole et al 2001;Dunham et al 2003;Boxall et al 2007). The attributes of thermal refuges that are most likely to determine the distribution of coldwater species are size, frequency, and connectivity between patches.…”

“…Salmonid fishes are coldwater species that require water temperatures in the range of 12-15 • C for optimal growth (Coutant 1977). Salmonids typically show signs of stress when maximum water temperature exceeds 22 • C for less than 1 d (Dickerson and Vinyard 1999;Dunham et al 2003;Johnstone and Rahel 2003) and may attempt to thermoregulate by finding coolwater refuges within larger areas that exceed stressful temperature levels (Ebersole et al 2001;Schrank et al 2003;Boxall et al 2007). Temperature alterations in rivers due to dams that release epilimnetic water have had unintended effects on the quantity, quality, and spatial arrangement of habitats used by coldwater species (Angilletta et al 2008).…”

The roles of Neogene geology and late Pleistocene lake levels in shaping the genetic structure of the Lahontan redside shinerRichardsonius egregius(Teleostei: Cyprinidae)

“…Because gene flow no longer occurs between McDermitt Creek and North Fork Little Humboldt River, the lack of genetic variation between those populations may be explained by insufficient time since isolation for mutations to accumulate in cyt b. Microsatellite data suggest populations of Lahontan cutthroat trout exhibit significant genetic variation within the Lahontan Basin (Neville, Dunham & Peacock, 2006). Also, topography affects migration patterns and gene flow, and thus population densities of Lahontan cutthroat trout in some streams (Boxall, Giannico & Li, 2008). Although our sampling was not sufficiently detailed to investigate migration patterns of R. egregius within drainages, it stands to reason that the same factors that contribute to population structure of Lahontan cutthroat trout within drainages might also contribute to population structure of R. egregius within drainages, and to the overall genetic diversity of the species.…”