Kodiak brown bears surf the salmon red wave: direct evidence from <scp>GPS</scp> collared individuals

Deacy, William W.; Leacock, William B.; Armstrong, Jonathan B.; Stanford, Jack A.

doi:10.1890/15-1060.1

Cited by 100 publications

(110 citation statements)

References 42 publications

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“…Because bears may forage along many streams over the course of the season (Barnes , Deacy et al. , Wirsing et al. ), small increases in consumption resulting from increased escapements, if realized across multiple foraging streams, could provide an ecologically meaningful increase in salmon consumption.…”

Section: Discussionmentioning

confidence: 99%

Managing salmon for wildlife: Do fisheries limit salmon consumption by bears in small Alaskan streams?

Lincoln

Hilborn

Wirsing

et al. 2020

Ecological Applications

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Ecosystem‐based management requires consideration of overlapping resource use between humans and other consumers. Pacific salmon are an important resource for both fisheries and populations of wildlife around the Pacific rim, including coastal brown bears (Ursus arctos); salmon consumption has been positively linked to bear density, body size, and reproductive rate. As a case study within the broader context of human–wildlife competition for food, we used 16–22 yr of empirical data in four different salmon‐bearing systems in southwestern Alaska to explore the relationship between sockeye salmon (Oncorhynchus nerka) availability and consumption by bears. We found a negative relationship between the annual biomass of salmon available to bears and the fraction of biomass consumed per fish, and a saturating relationship between salmon availability and the total annual biomass of salmon consumed by bears. Under modeled scenarios, bear consumption of salmon was predicted to increase only with dramatic (on the order of 50–100%) increases in prey availability. Even such large increases in salmon abundance were estimated to produce relatively modest increases in per capita salmon consumption by bears (2.4–4.8 kg·bear−1·d−1, 15–59% of the estimated daily maximum per capita intake), in part because bears did not consume salmon entirely, especially when salmon were most available. Thus, while bears catching salmon in small streams may be limited by salmon harvest in some years, current management of the systems we studied is sufficient for bear populations to reach maximum salmon consumption every 2–4 yr. Consequently, allocating more salmon for brown bear conservation would unlikely result in an ecologically significant response for bears in these systems, though other ecosystem components might benefit. Our results highlight the need for documenting empirical relationships between prey abundance and consumption, particularly in systems with partial consumption, when evaluating the ecological response of managing prey resources for wildlife populations.

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Section: Discussionmentioning

confidence: 99%

Managing salmon for wildlife: Do fisheries limit salmon consumption by bears in small Alaskan streams?

Lincoln

Hilborn

Wirsing

et al. 2020

Ecological Applications

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“…), and bears (Deacy et al. ). The food resources produced from within the lake available to seals include abundant juvenile sockeye salmon and a diverse array of resident fishes, all of which would isotopically reflect lake water (Figs.…”

Section: Discussionmentioning

confidence: 99%

“…; Deacy et al. ). Once constrained, the degree to which sockeye salmon isotopically changed over the course of spawning enabled us to test different hypotheses regarding whether Iliamna harbor seals migrate to the ocean and the extent to which they exploit trophic resources produced from within the lake versus the ocean.…”

Section: Introductionmentioning

confidence: 99%

Isotopes in teeth and a cryptic population of coastal freshwater seals

Brennan

Fernández

Burns

et al. 2019

Conservation Biology

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Human activities threaten the biodiversity of aquatic mammals across the globe. Conservation of these species hinges on the ability to delineate movements and foraging behaviors of animals, but gaining such insights is hampered by difficulties in tracing individuals over their lives. We determined isotope ratios in teeth (87Sr/86Sr, 13C/12C, and 18O/16O) to examine lifelong movement and resource‐use patterns of a unique freshwater population of a wide‐ranging pinniped species (harbor seal [Phoca vitulina]) that resides in Iliamna Lake, Alaska (U.S.A.). This population's potentially unique migratory behavior and use of different trophic resources are unknown. The isotope ratios we measured in teeth showed that seals were born in the lake, remained lifelong residents, and relied principally on resources produced from in the lake, even when seasonally abundant and nutrient‐dense spawning anadromous fish (i.e., sockeye salmon [Oncorhynchus nerka]) were available in the lake. Our results illustrate how serial isotope records in teeth, particularly 87Sr/86Sr ratios, can be used to quantify how coastal mammal populations exploit both freshwater and marine ecosystems. Understanding lifelong patterns of habitat and resource use is essential information when designing effective conservation plans for threatened coastal mammals. We present the Iliamna Lake harbor seals as a unique case study into how isotope records within teeth can help reveal the cryptic ecology of such a population residing in an intact ecosystem. The results also provide critical baseline information for the Kvichak River system, which is facing an uncertain future due to proposed large‐scale industrial development and a rapidly changing climate.

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“…We collected morphology data in our study streams using established methods (Deacy et al. ). Using an equation to predict mean RLS is not as robust as measuring it in situ.…”

Section: Methodsmentioning

confidence: 99%

Variation in spawning phenology within salmon populations influences landscape‐level patterns of brown bear activity

et al. 2019

Self Cite

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Animal consumers track spatial variation in resource phenology (i.e., resource waves) to prolong their access to ephemeral foods. While recent work has revealed how animals move across landscapes to exploit phenological variation among discrete foraging patches, much less is known about how variation nested within patches influences the spatiotemporal pattern of foraging opportunities and the behavior of consumers. Local, within-patch, variation in phenology influences levels of resource ephemerality and could dictate how frequently consumers must move to continuously exploit a pulsed food source. Here, we explore how within-site (stream) phenological variation relates to the duration of salmon (Oncorhynchus nerka) runs and its consequences for brown bear (Ursus arctos middendorffi) foraging behavior. We accurately quantified salmon run duration across a large number of spawning streams (21 site-year combinations). We found that salmon run duration varied threefold among spawning sites and that the source of prolonged runs was within-site variation in spawning phenology (i.e., the timing of arrival at spawning grounds). Although the estimated reproductive lifespan varied among sites, a simulation suggested that reproductive lifespan has little influence on salmon run duration. Salmon run duration strongly predicted the duration of site occupancy by bears, demonstrating that phenological variation within salmon populations compliments among-population variation to alleviate time constraints on salmon consumption. To explore whether within-population variation in salmon phenology was related to spatial variation in habitat conditions (as is the case with among-population phenological variation), we monitored water temperature, salmon availability, and bear activity across a longitudinal gradient in Connecticut Creek, the study stream with the most prolonged salmon run. Spawn timing varied spatially, occurring first in cold headwater reaches and later in warmer downstream reaches. Patterns of bear presence closely tracked this spawning sequence, suggesting they "surf salmon waves" not only across landscapes but also within spawning sites. However, a coarser analysis across multiple sites suggests phenological variation within salmon populations may not always be spatially structured. Our results demonstrate one way in which local variation in phenology can influence consumer foraging behavior, highlighting the need to understand the causes and consequences of phenological variation at multiple scales.

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Kodiak brown bears surf the salmon red wave: direct evidence from GPS collared individuals

Cited by 100 publications

References 42 publications

Managing salmon for wildlife: Do fisheries limit salmon consumption by bears in small Alaskan streams?

Managing salmon for wildlife: Do fisheries limit salmon consumption by bears in small Alaskan streams?

Isotopes in teeth and a cryptic population of coastal freshwater seals

Variation in spawning phenology within salmon populations influences landscape‐level patterns of brown bear activity

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