Spatiotemporal patterns of mountain whitefish (Prosopium williamsoni) in response to a restoration of longitudinal connectivity

Abstract

To examine the role of longitudinal connectivity on the spatial and temporal dynamics of mountain whitefish (Prosopium williamsoni), we quantified movement and population dynamics following installation of the Landsburg Dam fishway, Cedar River, WA, USA. Mountain whitefish is widely distributed, poorly studied and not the focus of restoration. Before the fishway, mountain whitefish were not observed above the dam. Here, we focus on snorkel counts collected at reach and mesohabitat (e.g. pools) scales over 11 summers on the 20‐km above‐dam segment following restoration. A camera within the ladder provided number, size and movement timing, thereby informing on behaviour and recolonisation. Segment‐scale abundance increased following fish passage reaching an asymptote in 7 years, and mountain whitefish were detected throughout the main stem in 10 years. Annual movement through the ladder increased over time and was positively correlated with instream abundance and discharge, but negatively correlated with water temperature. About 60% of fish movements occurred in spring and early summer, potentially for foraging opportunities. Reach‐scale abundance peaked between 7 and 10 km from the dam; deep, cool (~10.6 to 11.6°C) conditions characterised these reaches. At the mesohabitat scale, mountain whitefish detection increased with depth and velocity after accounting for distance from the dam. Our results show how restoring longitudinal connectivity allowed this nontarget species to colonise newly available habitat. Their response supports the critical roles of longitudinal connectivity and environmental conditions, that manifest at different spatial scales, in dictating how freshwater fish respond to habitat disturbance.

Passive Integrated Transponder Tag Monitoring Reveals Complex Migration and Life History Patterns in Mountain Whitefish in Upper Columbia River Tributaries

“…While we are unaware of the exact habitat or nutritional resources being exploited by these fish, we speculate that tributary habitats are important in the spring because tributaries provide better environmental conditions or nutritional benefits for aquatic foraging than do main-stem habitats. This conclusion is consistent with other researchers studying seasonal movement patterns of Mountain Whitefish (e.g., Davies and Thompson 1976;Baxter 2002;Kiffney et al 2018). Twisp River entry timing is just prior to the typical peak in discharge that occurs approximately in mid-May.…”

Colonization of a temperate river by mobile fish following habitat reconnection

“…As coho salmon densities increased over time in these reaches, our results indicate that upstream expansion resulted from dispersal of juveniles and adults from these initial core habitats to use underexploited upstream habitat for spawning and rearing, in addition to random adults straying from below the dam (Anderson et al, 2013, 2015). We speculate mountain whitefish were responding to the upstream distribution of cool, food‐rich, deepwater foraging habitats necessary to support the relatively large aggregations (~20–40 individuals) of large‐bodied individuals (Kiffney, Cram, et al, 2018; Rosenfeld & Taylor, 2009). These cool, deepwater conditions are relatively abundant in the high‐gradient reaches (CR3, CR5, and CR7) dispersed across the 15 km of main stem habitat primarily used by this species, and may have acted as stepping stones for upstream expansion.…”

“…Earlier reports from the Landsburg Dam fish passage research focused on the shorter term (<10 years) recolonization response, mostly at the population level (e.g., Anderson & Quinn, 2007). Collectively, these studies indicated rapid dispersal above the dam after restoration of fish passage in September 2003, followed by increased abundance, and spatial expansion of coho and Chinook salmon (Anderson et al, 2015; Anderson & Quinn, 2007; Burton et al, 2013; Kiffney et al, 2009; Pess et al, 2011) and mountain whitefish from the site of restoration (Kiffney, Cram, et al, 2018). Other studies provide little evidence of ecological change (i.e., density, growth, survival, movement) in resident fish following restoration and subsequent coho salmon colonization of Rock Creek (Salmonidae: Buehrens et al, 2014; Cottidae: Naman et al, 2014), a tributary to the main stem Cedar River located a few kilometers upstream of the dam.…”

“…First, we predicted either positive linear or asymptotic restoration response trajectories (abundance, biomass, and compositional diversity), because of initially abundant and underexploited, high‐quality riverine habitat (Pess et al, 2011), and nearby source populations (Ahlroth et al, 2003; Pess et al, 2012; Simberloff & Wilson, 1970; Veit & Lewis, 1996). A positive linear increase in the response of interest at the end of monitoring indicates ongoing recovery, whereas a positive, asymptotic function indicates a slowing in the recovery rate, at least temporarily, possibly due to negative density dependence and other environmental constraints (Ahlroth et al, 2003; Heino et al, 2016; Kiffney, Cram, et al, 2018). Second, we expected response trajectories to vary due to differences in species (Anderson et al, 2015; Anderson & Quinn, 2007; Sheldon & Meffe, 1995); life stage (Voelz et al, 1994; Williams et al, 2010); distance from the dam and presumed source populations below (Kiffney, Cram, et al, 2018; Thomas & Harrison, 1992); and annual variation in abiotic (Anderson & Quinn, 2007; Kiffney, Cram, et al, 2018; Lobón‐Cerviá, 2014) and biotic conditions (Grossman & Simon, 2019).…”

Population response to connectivity restoration of high elevation tropical stream reaches in Hawai'i

“…We found tangible benefits to shrimp populations in 2012 in streams with partial flow restoration for 2 years relative to no flow restoration, and greater benefits for streams following 2 years of full restoration in 2017. Kiffney et al (2018) found that following the augmentation of a migration barrier in a Washington river, mountain whitefish ( Prosopium williamsoni ) reestablished above the former barrier quickly, but densities did not asymptote until year 7 and the maximum extent of reestablishment was reached only after a decade. These results support the growing literature identifying the benefits of restoring flow regimes to biota and ecosystem processes (Palmer & Ruhi, 2019).…”