Interactions of baseflow habitat constraints: Macroinvertebrate drift, stream temperature, and physical habitat for anadromous salmon in the Calapooia River, Oregon

Abstract

1. The Calapooia River in western Oregon supports a small winter steelhead trout (Oncorhynchus mykiss) population and historically supported spring Chinook salmon (Oncorhynchus tshawytscha). Early timber harvesting removed the riparian forest, and log transportation practices simplified the channel. Those disturbance legacies continue to affect fish habitat by limiting shade and channel complexity, complicating conservation efforts.2. To evaluate juvenile salmonid rearing potential, macroinvertebrate drift, thermal regime and physical habitat were measured at eight sites in 24 km of the upper river during late summer baseflow.3. Overall physical habitat was simple, with few functioning instream structures or pools. During the 22-day drift study, flows declined and maximum site stream temperatures ranged from 23.1°C at the lower end to 16.4°C 24 km upstream.4. Macroinvertebrate drift concentrations ranged from 0.7-13.7 ind. m −3 with biomasses from 0.02-1.23 mg m −3 . Drift concentration biomass was higher upstream (P = 0.006) than downstream and declined overall (P < 0.001) during the study. Drift biomass was dominated by five taxon groups -Baetis tricaudatus, Calineuria californica, Hesperoperla pacifica, Simulium spp., and Chironomidae, which were 65% of total biomass. During twilight, total biomass and biomass of B. tricaudatus, Simulium spp., and Chironomidae (both larvae and adults) were higher. 5. Total drift declined dramatically over the study period owing to decreases in drift concentration and a 58% decline in discharge, greatly reducing overall drift and available food resources for juvenile-rearing salmonids.6. The upper catchment, both with cooler temperatures and higher food availability, provided the best conditions for juvenile anadromous salmonids to survive late summer conditions. Conservation consequences of climate change-induced alterations in flow and temperature may further affect habitat quality for juvenile salmonids in this catchment in the coming decades.

Developing flow–ecology relationships: Implications of nonlinear biological responses for water management

“…However, Hayes et al (2016) observed the opposite pattern, where drift concentration decreased with flow in the Mataura River, New Zealand (Figure 6b). The response of drift to changing flow is highly context-dependent (Naman et al, 2016), and while evidence to date indicates that overall flux of prey to salmonids consistently declines at lower discharge (Danehy, Bilby, Owen, Duke, & Farrand, 2017;Hayes, et al, 2016;Sotiropoulos, Nislow, & Ross, 2006;Wooster et al, 2016), the consistency of flow-related changes in drift concentration remains unclear. Declining flow may reduce drift concentration if the surface area of drift-producing riffle habitat decreases (Naman et al, 2016); alternatively, shrinking wetted habitat may increase density-dependent competition for resources among benthic invertebrates and elevate behavioural invertebrate drift (James, Dewson, & Death, 2008).…”

“…Declining flow may reduce drift concentration if the surface area of drift-producing riffle habitat decreases (Naman et al, 2016); alternatively, shrinking wetted habitat may increase density-dependent competition for resources among benthic invertebrates and elevate behavioural invertebrate drift (James, Dewson, & Death, 2008). However, even increased drift concentration on a declining hydrograph is insufficient to reverse the overall negative impact of declining flow on total energy flux (Danehy et al, 2017;Wooster et al, 2016).…”

Drainage from the Critical Zone: Lithologic Controls on the Persistence and Spatial Extent of Wetted Channels during the Summer Dry Season

“…Water temperature strongly controls stream biota survival (e.g., Ray et al, ), and transiently wetted channel stretches create gaps that trap and isolate aquatic species that lack the ability to survive in the hyporheic zone (e.g., Jaeger et al, ). Fluctuations in water temperature and wetted channel network (WCN) extent affect the habitat connectivity and health of salmonid species, including steelhead ( Onchorhynchus mykiss ) and coho ( Onchorhynchus kisutch ) (e.g., Danehy et al, ; Kelson et al, ; Schaaf et al, ). Furthermore, transiently wetted stretches can produce hypoxic backwater events that can be devastating for certain populations (e.g., Hladyz et al, ).…”

The Impact of Hydropeaking on Juvenile Brown Trout (Salmo trutta) in a Norwegian Regulated River

“…Hydropeaking may also reduce the quality of fish habitat and change fish community structures by changes in current speed [15,16] and by the stranding of invertebrates [17]. Benthic macroinvertebrates are potentially vulnerable in shallow riffle habitats [18,19]. Invertebrate abundance in rivers affected by hydropeaking demonstrates a lateral gradient from the most exposed areas having a low overall abundance through to the permanently wetted zone, which has invertebrate abundance and diversity similar to natural systems or unaffected reaches [20,21].…”