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6 records – page 1 of 1.

Aerial surveys cause large but ephemeral decreases in bear presence at salmon streams in Kodiak, Alaska.

https://arctichealth.org/en/permalink/ahliterature309083
Source
PLoS One. 2019; 14(9):e0222085
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Date
2019
Author
William W Deacy
William B Leacock
Eric J Ward
Jonathan B Armstrong
Author Affiliation
Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR, United States of America.
Source
PLoS One. 2019; 14(9):e0222085
Date
2019
Language
English
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Keywords
Alaska
Animal Distribution
Animals
Biomass
Ecosystem
Female
Male
Remote Sensing Technology - adverse effects - methods - standards
Rivers
Salmon - physiology
Ursidae - physiology
Abstract
Aerial surveys are often used to monitor wildlife and fish populations, but rarely are the effects on animal behavior documented. For over 30 years, the Kodiak National Wildlife Refuge has conducted low-altitude aerial surveys to assess Kodiak brown bear (Ursus arctos middendorffi) space use and demographic composition when bears are seasonally congregated near salmon spawning streams in southwestern Kodiak Island, Alaska. Salmon (Oncorhynchus spp.) are an important bear food and salmon runs are brief, so decreases in time spent fishing for salmon may reduce salmon consumption by bears. The goal of this study was to apply different and complementary field methods to evaluate the response of bears to these aerial surveys. Ground-based counts at one stream indicated 62% of bears departed the 200m-wide survey zone in response to aerial surveys, but bear counts returned to pre-survey abundance after only three hours. Although this effect was brief, survey flights occurred during the hours of peak daily bear activity (morning and evening), so the three-hour disruption appeared to result in a 25% decline in cumulative daily detections by 38 time-lapse cameras deployed along 10 salmon streams. Bear responses varied by sex-male bears were much more likely than female bears (with or without cubs) to depart streams and female bears with GPS collars did not move from streams following surveys. Although bears displaced by aerial surveys may consume fewer salmon, the actual effect on their fitness depends on whether they compensate by foraging at other times or by switching to other nutritious resources. Data from complementary sources allows managers to more robustly understand the impacts of surveys and whether their benefits are justified. Similar assessments should be made on alternative techniques such as Unmanned Aerial Vehicles and non-invasive sampling to determine whether they supply equivalent data while limiting bear disturbance.
PubMed ID
31504063 View in PubMed
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Inter-Tributary Movements by Resident Salmonids across a Boreal Riverscape.

https://arctichealth.org/en/permalink/ahliterature266147
Source
PLoS One. 2015;10(9):e0136985
Publication Type
Article
Author
Kale T Bentley
Daniel E Schindler
Jonathan B Armstrong
Timothy J Cline
Gabriel T Brooks
Source
PLoS One. 2015;10(9):e0136985
Language
English
Publication Type
Article
Abstract
Stream-dwelling fishes inhabit river networks where resources are distributed heterogeneously across space and time. Current theory emphasizes that fishes often perform large-scale movements among habitat patches for reproduction and seeking refugia, but assumes that fish are relatively sedentary during growth phases of their life cycle. Using stationary passive integrated transponder (PIT)-tag antennas and snorkel surveys, we assessed the individual and population level movement patterns of two species of fish across a network of tributaries within the Wood River basin in southwestern Alaska where summer foraging opportunities vary substantially among streams, seasons, and years. Across two years, Arctic grayling (Thymallus arcticus) and rainbow trout (Oncorhynchus mykiss) exhibited kilometer-scale movements among streams during the summer growing season. Although we monitored movements at a small fraction of all tributaries used by grayling and rainbow trout, approximately 50% of individuals moved among two or more streams separated by at least 7 km within a single summer. Movements were concentrated in June and July, and subsided by early August. The decline in movements coincided with spawning by anadromous sockeye salmon, which offer a high-quality resource pulse of food to resident species. Inter-stream movements may represent prospecting behavior as individuals seek out the most profitable foraging opportunities that are patchily distributed across space and time. Our results highlight that large-scale movements may not only be necessary for individuals to fulfill their life-cycle, but also to exploit heterogeneously spaced trophic resources. Therefore, habitat fragmentation and homogenization may have strong, but currently undescribed, ecological effects on the access to critical food resources in stream-dwelling fish populations.
PubMed ID
26379237 View in PubMed
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Kodiak brown bears surf the salmon red wave: direct evidence from GPS collared individuals.

https://arctichealth.org/en/permalink/ahliterature274570
Source
Ecology. 2016 May;97(5):1091-8
Publication Type
Article
Date
May-2016
Author
William Deacy
William Leacock
Jonathan B Armstrong
Jack A Stanford
Source
Ecology. 2016 May;97(5):1091-8
Date
May-2016
Language
English
Publication Type
Article
Keywords
Alaska
Animal Identification Systems - instrumentation
Animal Migration - physiology
Animals
Feeding Behavior - physiology
Geographic Information Systems
Salmon - physiology
Time Factors
Ursidae - physiology
Abstract
A key constraint faced by consumers is achieving a positive energy balance in the face of temporal variation in foraging opportunities. Recent work has shown that spatial heterogeneity in resource phenology can buffer mobile consumers from this constraint by allowing them to track changes in resource availability across space. For example, salmon populations spawn asynchronously across watersheds, causing high-quality foraging opportunities to propagate across the landscape, prolonging the availability of salmon at the regional scale. However, we know little about how individual consumers integrate across phenological variation or the benefits they receive by doing so. Here, we present direct evidence that individual brown bears track spatial variation in salmon phenology. Data from 40 GPS collared brown bears show that bears visited multiple spawning sites in synchrony with the order of spawning phenology. The number of sites used was correlated with the number of days a bear exploited salmon, suggesting the phenological variation in the study area influenced bear access to salmon, a resource which strongly influences bear fitness. Fisheries managers attempting to maximize harvest while maintaining ecosystem function should strive to protect the population diversity that underlies the phenological variation used by wildlife consumers.
PubMed ID
27349087 View in PubMed
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Phenotype flexibility in wild fish: Dolly Varden regulate assimilative capacity to capitalize on annual pulsed subsidies.

https://arctichealth.org/en/permalink/ahliterature257678
Source
J Anim Ecol. 2013 Sep;82(5):966-75
Publication Type
Article
Date
Sep-2013
Author
Jonathan B Armstrong
Morgan H Bond
Author Affiliation
School of Aquatic and Fishery Sciences, University of Washington, Box 355020, Seattle, WA, 98195, USA.
Source
J Anim Ecol. 2013 Sep;82(5):966-75
Date
Sep-2013
Language
English
Publication Type
Article
Keywords
Alaska
Animals
Atrophy
Diet
Digestive System Physiological Phenomena
Eggs
Energy Metabolism
Liver - physiology
Phenotype
Rivers
Salmon
Temperature
Trout - growth & development - physiology
Abstract
1. Large digestive organs increase rates of energy gain when food is plentiful but are costly to maintain and increase rates of energy loss when food is scarce. The physiological adaptations to this trade-off differ depending on the scale and predictability of variation in food abundance. 2. Currently, there is little understanding of how animals balance trade-offs between the cost and capacity of the digestive system in response to resource pulses: rare, ephemeral periods of resource superabundance. We investigated the physiological and behavioural tactics of the fish Dolly Varden (Salvelinus malma) that rear in watersheds with low in situ productivity, but experience annual resource pulses from the spawning migrations of Pacific salmon. The eggs of Pacific salmon provide high-energy food for Dolly Varden. 3. Dolly Varden sampled 6 weeks prior to the resource pulse exhibited atrophy of the stomach, pyloric caeca, intestine and liver. Throughout the portion of the growing season prior to the resource pulse, fish exhibited empty stomachs, low indices of energy condition and muscle isotope signatures reflecting the previous resource pulse. 4. During the resource pulse, Dolly Varden exhibited large digestive machinery, gorged on salmon eggs and rapidly stored energy in fat reserves, somatic growth and gonad development. Dolly Varden appeared to achieve nearly their entire annual energy surplus during the ~ 5-week period when sockeye salmon spawn. 5. Digestive flexibility provides Dolly Varden the energy efficiency required to survive and reproduce when resource abundance is concentrated into an annual pulse that is predictable, yet highly ephemeral. Although fish are known to incur extremely variable energy budgets, our study is one of the first to document digestive flexibility in wild fish. Our study emphasizes that fish can rely heavily on rare, high-magnitude foraging opportunities. Human actions that attenuate spikes in food abundance may have stronger than anticipated effects on consumer energy budgets.
PubMed ID
23510107 View in PubMed
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Predator avoidance during reproduction: diel movements by spawning sockeye salmon between stream and lake habitats.

https://arctichealth.org/en/permalink/ahliterature271618
Source
J Anim Ecol. 2014 Nov;83(6):1478-89
Publication Type
Article
Date
Nov-2014
Author
Kale T Bentley
Daniel E Schindler
Timothy J Cline
Jonathan B Armstrong
Daniel Macias
Lindsy R Ciepiela
Ray Hilborn
Source
J Anim Ecol. 2014 Nov;83(6):1478-89
Date
Nov-2014
Language
English
Publication Type
Article
Keywords
Alaska
Animals
Avoidance Learning
Circadian Rhythm
Ecosystem
Female
Food chain
Lakes
Male
Movement
Predatory Behavior
Reproduction
Rivers
Salmon - physiology
Ursidae - physiology
Abstract
Daily movements of mobile organisms between habitats in response to changing trade-offs between predation risk and foraging gains are well established; however, less in known about whether similar tactics are used during reproduction, a time period when many organisms are particularly vulnerable to predators. We investigated the reproductive behaviour of adult sockeye salmon (Oncorhynchus nerka) and the activity of their principal predator, brown bears (Ursus arctos), on streams in south-western Alaska. Specifically, we continuously monitored movements of salmon between lake habitat, where salmon are invulnerable to bears, and three small streams, where salmon spawn and are highly vulnerable to bears. We conducted our study across 2 years that offered a distinct contrast in bear activity and predation rates. Diel movements by adult sockeye salmon between stream and lake habitat were observed in 51.3% ± 17.7% (mean ± SD) of individuals among years and sites. Fish that moved tended to hold in the lake for most of the day and then migrated into spawning streams during the night, coincident with when bear activity on streams tended to be lowest. Additionally, cyclic movements between lakes and spawning streams were concentrated earlier in the spawning season. Individuals that exhibited diel movements had longer average reproductive life spans than those who made only one directed movement into a stream. However, the relative effect was dependent on the timing of bear predation, which varied between years. When predation pressure primarily occurred early in the spawning run (i.e., during the height of the diel movements), movers lived 120-310% longer than non-movers. If predation pressure was concentrated later in the spawning run (i.e. when most movements had ceased), movers only lived 10-60% longer. Our results suggest a dynamic trade-off in reproductive strategies of sockeye salmon; adults must be in the stream to reproduce, but must also avoid predation long enough to spawn. Given the interannual variation in the timing and intensity of predation pressure, the advantages of a particular movement strategy will likely vary among years. Regardless, movements by salmon allowed individuals to exploit fine-scale habitat heterogeneity during reproduction, which appears to be a strategy to reduce predation risk on the spawning grounds.
PubMed ID
24702169 View in PubMed
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Thermal heterogeneity mediates the effects of pulsed subsidies across a landscape.

https://arctichealth.org/en/permalink/ahliterature96829
Source
Ecology. 2010 May;91(5):1445-54
Publication Type
Article
Date
May-2010
Author
Jonathan B Armstrong
Daniel E Schindler
Kristen L Omori
Casey P Ruff
Thomas P Quinn
Author Affiliation
School of Aquatic and Fishery Sciences, Box 355020, University of Washington, Seattle, Washington 98195, USA. jonny99@u.washington.edu
Source
Ecology. 2010 May;91(5):1445-54
Date
May-2010
Language
English
Publication Type
Article
Keywords
Animals
Body Size
Ecosystem
Feeding Behavior
Fishes - physiology
Rivers
Seasons
Temperature
Time Factors
Abstract
Spatial and temporal heterogeneity interact to make the foraging rates of individuals more variable than expected from models assuming that spatial and temporal dimensions of habitat conditions operate independently. For example, trophic resource pulses produce temporal patches of prey superabundance, yet little is known about how spatial heterogeneity in habitat conditions mediates the ability of consumers to exploit these high-quality foraging opportunities. We studied how spatial variation in water temperature regulates the potential for juvenile coho salmon to exploit a seasonal pulsed subsidy of eggs produced by anadromous sockeye salmon. Streams within the Wood River watershed, southwestern Alaska, USA, ranged in mean summer temperature from 3.6 degrees to 14.5 degrees C. Growth of juvenile coho prior to the arrival of the seasonal egg subsidy was positively related to water temperature among streams. An in situ experiment combined with field samples of diets revealed a size threshold for egg consumption; only individuals longer than approximately 70 mm could consume eggs due to gape limitation of smaller individuals. A bioenergetics simulation demonstrated that water temperature regulated whether age-0 coho salmon could grow large enough to exceed the size threshold for egg consumption. Coho salmon that consumed eggs had energy rations that were five times higher than fish that did not consume eggs, resulting in a positive feedback of water temperature on their integrated seasonal growth. Across this landscape, heterogeneity in water temperature mediates individual- and population-level responses to seasonally available resource pulses. Our study illustrates that ecological mechanisms, such as size-based foraging asymmetries, can magnify the effects of climate change compared to predictions based on physiology alone.
PubMed ID
20503876 View in PubMed
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6 records – page 1 of 1.