The submerged and floating plant communities in floodplain wetlands of the Upper Columbia River have never been described. To explore mechanisms behind the influence of the annual flood pulse on vegetation, we investigated how species group into flood response guilds whose distributions vary along a connectivity gradient between 44 floodplain wetlands and the river, how connectivity influences water and sediment, and to what degree the effect of connectivity on vegetation is mediated by its effects on these environmental variables. We characterised assemblages with cluster and indicator species analysis, as well as non-metric scaling ordination and tested a structural equation model, which defined the relationship between assemblage composition, sediment and water quality, and connectivity to the river. We found four assemblages, each associated with different water and sediment conditions, and positioned at differing degrees of connectivity. The model provided a good fit to the data. We conclude that in highly connected floodplain wetlands the direct effect of flooding supersedes the influence of water and sediment quality in structuring vegetation assemblages. Yet where flooding is less intense, these environmental variables resume their structuring role.

Dams represent one of the major forms of river alteration. As these structures reach the end of their lifespan, they often require extensive refurbishments or removal. A small-scale water supply dam in Banff National Park (Alberta, Canada) was partially removed, creating a breach that allowed water to scour a new passage resembling a nature-like fishway. We investigated the permeability of the partially removed dam as a means of validating the conservation benefits of the partial dam removal.We quantified the proportion of bull trout (Salvelinus confluentus), a threatened species in Canada, that approached and passed the fishway using radio telemetry receiver stations. The proportion of bull trout that approached the fishway was low (37.0%; N = 27 of 73), but was consistent with upstream reference sites (33%; N = 20 of 60). For those that did approach, the proportion of bull trout that passed yielded a high passage efficiency (77.8%; N = 21 of 27 that approached). The probability that a fish passed the fishway was related to water depth and time of day. Bull trout were more likely to pass when water depths were high (>0.40 m), and at night. Passage duration ranged from 5-mins to 13-days, suggesting that this resident species used the fishway for a variety of purposes (e.g., station holding and foraging) and not just transiting. Some individuals underwent large-scale movements 2-km upstream (15.1%; N = 11 of 73), or 2-km downstream (2.7%; N = 2 of 73) following a successful passage event. This study provides new insight on how, in some instances, a breach in a dam can function as a nature-like fishway, accommodatingyear-round stream flows and providing hydraulic conditions suitable for fish passage without costly engineering or construction.

The intentional introduction of native cold‐water trout into high‐elevation fishless lakes has been considered a tool to build resilience to climate change (i.e., assisted colonization); however, ecological impacts on recipient communities are understudied. The purpose of this study was to inform native cold‐water trout recovery managers by assessing potential consequences of translocating a regionally native trout (westslope cutthroat trout; Oncorhynchus clarkii lewisi) into fishless mountain lakes. This study compared littoral benthic invertebrate richness, diversity, community structure and abundance between three groups of lakes (fishless, native trout, nonnative trout) in the Canadian Rocky Mountains. While richness and diversity were preserved across all lake groups, other lines of evidence suggested that the introduction of native westslope cutthroat trout into fishless lakes can alter littoral benthic invertebrate communities in similar ways as nonnative brook trout (Salvelinus fontinalis). The community structure of cutthroat trout lakes resembled brook trout lakes compared to that of fishless lakes. For example, both trout‐lake groups contained a lower density of free‐swimming ameletid mayflies and a higher density of certain burrowing taxa. Risk assessments for trout‐recovery actions should consider the potential for collateral damage to recipient invertebrate communities. Future research should identify possible cascading trophic effects on species subsidized by invertebrate prey.

No abstract

Background Fixed radio telemetry stations are used to study the movement ecology of fishes in streams and rivers. A common assumption of such studies is that detection efficiency remains constant through space and time. The objective of this study was to understand how site characteristics and tag distance can influence the detection efficiency of a fixed receiver when used for fisheries research in a small stream. Field tests included a fixed receiver station on Forty Mile Creek, in Banff National Park, AB, Canada that recorded signals from radio tags over specified distances (i.e., 0 m, 27 m, 53 m, 80 m) within the expected detection range from July to October, 2016. Model selection was used to test which parameters may influence detection efficiency. Results The fixed receiver was able to record an average of 89% of transmissions over the study period. Detection efficiency was greater or equal to 0.97 at tag distances of ≤ 53 m. Detection efficiency significantly declined by 36% to a rate of 0.62 for tags placed 80 m from the fixed receiver. Water temperature and water depth also reduced detection efficiency, but only at the critical threshold of 80 m from the tag. Interestingly, turbidity had no influence on detection efficiency in this study. Conclusions This study provided insights into the reliability of fixed receiver stations as a passive tracking technique in small streams. The abrupt change in detection efficiency observed in this study presumably occurs in other systems. Identifying critical detection distance thresholds would appear to be a useful strategy for avoiding false-negative results. It is recommended that researchers who conduct radio tracking studies with fixed arrays should consider the deployment of sentinel tags over the study to understand the system performance.