Consequences of actively managing a small Bull Trout population in a fragmented landscape

Robert K. Al-Chokhachy; Sean Moran; Peter McHugh; Shana Bernall; Wade Fredenberg; Joseph M. DosSantos

doi:10.1080/00028487.2015.1007162

Home/Archive/USGS

USGS · 70191691

Consequences of actively managing a small Bull Trout population in a fragmented landscape

Robert K. Al-Chokhachy·Sean Moran·Peter McHugh·Shana Bernall·Wade Fredenberg·Joseph M. DosSantos

View original source ↗Export metadata ↓

Abstract

Habitat fragmentation, which affects many native salmonid species, is one of the major factors contributing to the declines in distribution and abundance of Bull Trout Salvelinus confluentus . Increasingly, managers are considering options to maintain and enhance the persistence of isolated local populations through active management strategies. Understanding the ecological consequences of such actions is a necessary step in conservation planning. We used an individual-based model to evaluate the consequences of an ongoing management program aimed at mitigating the anthropogenic fragmentation of the lower Clark Fork River in Montana. Under this program juvenile Bull Trout are trapped and transported from small, headwater source populations to Lake Pend Oreille, Idaho, for rearing, and adults are subsequently recaptured in their upstream migration and returned to the natal population for spawning. We examined one of these populations and integrated empirical estimates of demographic parameters to simulate different management scenarios where moderate ( n = 4) and high ( n = 8) numbers of age-2, age-3, or age-4 Bull Trout were removed for transport with variable return rates under both demographic stochasticity and environmental perturbations. Our results indicated the risks from removal with no returns increased substantially when removal totals and age of Bull Trout removed from the simulated population increased. Specifically, removing eight age-3 or age-4 individuals resulted in 26% and 62% reductions in average adult population size, respectively, across simulations. We found the risks of transport were not likely alleviated with low (3%) or moderate (6%) return rates, and there were considerable risks of declines for the source population even when return rates were extremely high (>12%). Our simulations indicated little risk of declines for the source population with removals of age-2 Bull Trout, and any risks were alleviated with low return rates. However, we found higher return rates were particularly beneficial in the presence of large, density-independent perturbations.

Explore related subjects

Transactions of the American Fisheries Society Article

Source-reported bounding extent: 47.344406158662125° to 48.367198426439465° latitude; -116.73248291015624° to -115.01861572265624° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Robert K. Al-Chokhachy, Sean Moran, Peter McHugh, Shana Bernall, Wade Fredenberg, Joseph M. DosSantos. 2015-04-22. Consequences of actively managing a small Bull Trout population in a fragmented landscape. https://doi.org/10.1080/00028487.2015.1007162

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Effects of temperature on standard metabolic rate, hypoxia tolerance, and critical thermal maxima in invasive cichlids

Objective Jaguar Guapote Parachromis managuensis and Red Devil/Midas cichlids Amphilophus spp. are highly invasive species in the family Cichlidae native to Central America. These cichlids are popular within the aquarium trade, leading to their broad introduction outside of their native range. Information about potential environmental plasticity of a species can improve predictions of invasion potential. In this respect, measures of environmental influences on metabolic rate and hypoxia tolerance are important for understanding limitations in adaptability and subsequently guiding the management of invasive species. Methods Standard metabolic rate (SMR), hypoxia tolerance, and critical thermal maxima (CT max ) were compared between Jaguar Guapote and Amphilophus spp. For SMR and hypoxia tolerance, a range of temperatures spanning subtropical to tropical environments (i.e., 22, 28, and 34°C) was used, followed by stepwise decreases in oxygen saturation until loss of equilibrium. Results Jaguar Guapote and Amphilophus spp. both had lower SMR at 28°C than at 34°C, SMR at 22°C was not different from either temperature. Both Jaguar Guapote and Amphilophus spp. were the most sensitive to hypoxia at the coolest temperature (22°C) relative to warmer temperatures (28°C and 34°C). Upper thermal tolerance (CT max ) was similar between species (∼42°C), although Jaguar Guapote were more resilient based on a higher agitation temperature and recovery following high temperature exposure. Conclusions These results indicate temperatures that are representative of their natural distribution (i.e., near 28°C) offer energetic savings for Jaguar Guapote and Amphilophus spp. relative to warmer temperatures (34°C), with cooler temperatures (22°C) having higher metabolic costs than expected. Both Jaguar Guapote and Amphilophus spp. are sensitive to hypoxia at cooler temperatures (22°C). Therefore, these species are relatively resilient to high temperatures, but low temperatures may restrict their invasiveness.

Transactions of the American Fisheries Society↗

USGS2026

The value of electronic tagging and tracking studies for understanding fish–hypoxia interactions

Objective Hypoxia (i.e., low dissolved oxygen availability) is a natural phenomenon but can also be induced by human activities (e.g., nutrient enrichment from runoff). Given that dissolved oxygen is essential for aquatic life, periods of hypoxia tend to have negative consequences (e.g., sublethal disturbances, mortality) for most fishes. Extensive laboratory research has documented hypoxia thresholds and physiological and behavioral outcomes for a variety of freshwater and marine fishes and there is also an extensive body of fieldwork assessing population-level responses (e.g., survival, distribution). Yet, studying how individual fish respond to hypoxia in the wild has proved challenging; electronic tagging and tracking tools (e.g., biotelemetry, biologging) have made it easier to study individual responses to hypoxia and complement other tools like hydroacoustics that tend to focus on population-level responses. Methods We review what has been learned from contemporary studies that employ electronic tagging and tracking tools to understand how fish respond to hypoxia in the wild. Topics explored include identifying and validating hypoxia thresholds, habitat compression, connectivity, mortality, physiological and bioenergetic consequences, and extreme weather conditions. We also consider what we have learned about evaluating various management plans for hypoxia and reflect on how electronic tags have also been used in aquaculture systems and in hybrid studies that combine laboratory and field research. We highlight fishes in Lake Erie as a research narrative to demonstrate how electronic tagging and tracking have markedly improved our understanding of a longstanding hypoxia issue. Results Our synthesis revealed that electronic tagging and tracking have provided critical information on how fish respond to hypoxia in the field, revealing complex trade-offs and compensatory mechanisms as well as cryptic hypoxia-induced mortality. Beyond just illuminating space use and mortality, tags equipped with various sensors are revealing how fish deal with hypoxia in real time in terms of physiology, bioenergetics, and behavior. Conclusions As electronic tagging and tracking methods experience further innovation and are increasingly applied to understand the effects of hypoxia on fish, we expect more unanticipated findings about the effects of hypoxia on fish in all aquatic ecosystems, which will strengthen our ability to manage and mitigate hypoxia. Combining tools and approaches (e.g., lab and field) is perhaps the best way to generate comprehensive understanding.

Transactions of the American Fisheries Society↗

USGS2026

Life history traits and population dynamics of Freshwater Drum across large river gradients

Objective Monitoring and assessment of nongame native fishes is limited, but conservation interest in these species is growing. Freshwater Drum Aplodinotus grunniens are a wide-ranging species that serve important functional roles and could serve as an indicator for similar but less common species. Our overall objectives were to quantify and compare population dynamic rates and life history of Freshwater Drum among study reaches in the upper Mississippi and Illinois rivers and relate these metrics to hypothesized environmental and anthropogenic factors. Methods We integrated recently collected age data with monitoring data to estimate age and size distributions, growth curves, maturation schedules, mortality rates, and young-to-adult ratios of Freshwater Drum in six study reaches spanning 1,500 km of river. Principal component analyses and linear regression were used to relate environmental and anthropogenic gradients (latitude, commercial harvest, hydrologic dynamics, primary productivity) to life history traits and population dynamic rates. Results We found latitudinal gradients in life history traits and population dynamic rates whereby Freshwater Drum in upstream, higher-latitude study reaches generally exhibited later maturity, slower growth, smaller maximum size, and lower mortality rates compared with those in lower-latitude study reaches. Further, young-to-adult ratios positively corresponded with chlorophyll- a concentration. No clear relationships were apparent between population dynamic rates and hydrologic variation or commercial harvest. Conclusions Latitude is an important structuring component of life history traits and population dynamics of Freshwater Drum in the upper Mississippi and Illinois rivers likely due to both temperature seasonality and disturbance regimes. The presence of demographic structure in a widespread, common species such as Freshwater Drum suggests similar patterns likely exist in other long-lived native fishes.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗