Responses to the Foraging/Predation Risk Trade-Off and Individual Variability in Population-Level Fitness Correlates

Polivka, Karl M.

doi:10.5402/2011/376083

Cited by 5 publications

(21 citation statements)

References 47 publications

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“…When prey biomass in the benthos is low, it could be advantageous for all size classes to occupy stream inflows because energetic requirements are also lower. Further experimentation is required to address the influence of these bioenergetic mechanisms, but other evidence from this study system shows that condition index in YOY C. asper is affected in a manner consistent with a strong foraging/predation risk trade‐off (Polivka, 2011).…”

Section: Discussionmentioning

confidence: 94%

“…Fish near the shore at dawn and dusk include aggregations of pelagic juvenile salmonids ( Onchorhynchus tschawytscha , O. nerka ; K. Polivka, unpubl. data) and an abundant population of Cottus asper (Polivka, 2011), the most numerous fish consumer of littoral benthic macroinvertebrates in this system. Individuals move near the shore at dusk to forage and potentially to escape predation from larger fishes off‐shore, such as bull trout ( Salvelinus confluentus ; unpubl.…”

Section: Methodsmentioning

confidence: 92%

“…Higher metabolic demands may result in reduced energetic reserves and individuals in this condition are predicted to take more risks to forage (e.g. Clark, 1994;Kotler et al, 2010;Polivka, 2011). Occupancy of the cooler inflow plots (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…During the day, individuals move off‐shore. Larger individuals (>65 mm SL) have been observed to cannibalise young‐of‐the‐year and life‐history traits such as growth, survival and body condition are affected by the foraging and predation risk trade‐off in this species (Pfister, 2003; Polivka, 2011). For eight streams that flow into the southern shore, we established plots (25 m 2 ) at the stream inflow to the lake (designated ‘inflow’) and at an otherwise similar littoral site 20–40 m away from each inflow (‘control’).…”

Section: Methodsmentioning

confidence: 99%

“…Alofs & Polivka, 2004; Klaassen, Nolet & Bankert, 2006; Polivka, 2007), sometimes resulting in shifts in the mean condition (or other traits correlated with fitness) of individuals in a population (e.g. Sinclair & Arcese, 1995; Polivka, 2011). The study of factors that affect resource matching is tractable where fish habitat selection is easily quantified.…”

Section: Introductionmentioning

confidence: 99%

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Stream inflow and predation risk affect littoral habitat selection by benthic fish

Polivka¹,

Friedli²,

Green³

2013

Freshwater Biology

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Summary 1. We examined small, fishless headwater streams to determine whether transport of macroinvertebrates into the littoral zone of an oligotrophic lake augmented food availability for Cottus asper, an abundant predatory fish in our study system. We sampled fish and macroinvertebrates during the recruitment and growth season of 2 years, either monthly (2004) or bi‐monthly (2005), to observe whether stream inputs increased prey availability and whether variation in total macroinvertebrate biomass was tracked by fish. 2. Observations from eight headwater streams indicated that streams did not increase the total macroinvertebrate biomass in the shallow littoral zone at stream inflows, relative to adjacent plots without stream inputs (controls). The taxonomic composition of stream macroinvertebrates drifting toward the lake differed from that in the littoral lake benthos itself, although there was no evidence of any species change in the composition of the littoral benthos brought about by stream inputs. 3. Although streams made no measurable contribution to the biomass or taxonomic composition of the littoral macroinvertebrate benthos, there was substantial temporal variation in biomass among the eight sites for each of the (n = 7) sample periods during which observations were made. Variation in total biomass was primarily a function of bottom slope and benthic substrata in the lake habitats. Dominant taxonomic groups were Baetidae, Ephemerellidae (two genera), Leptophlebiidae, Chironomidae (three subfamilies) and Perlodidae, although we did not determine the specific substratum affinities of each taxon. 4. Mixed effects linear models identified a significant interaction between macroinvertebrate biomass and plot type (stream inflow vs. control) associated with fish abundance. Across the observed range of macroinvertebrate biomass, fish showed a significant preference for stream inflows, but more closely tracked food availability in the controls. For young‐of‐the‐year (YOY), a negative effect of temperature was also included in the model, and we observed lower temperatures at stream inflows. However, abundance of predatory adults affected habitat selection for YOY. Lake‐bottom slope also accounted for variation in abundance in both fish models. 5. Our results suggest that the effect of fishless headwater streams on downstream fish may not always be through direct delivery of food. In this study system, fish preferred stream inflow plots, but this preference interacted with macroinvertebrate biomass in a manner that was difficult to explain. For YOY, predation risk was related to the preference for stream inflows, although the specific factor that mitigates predation risk remains poorly understood.

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Section: Discussionmentioning

confidence: 94%

Section: Methodsmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stream inflow and predation risk affect littoral habitat selection by benthic fish

Polivka¹,

Friedli²,

Green³

2013

Freshwater Biology

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Habitat affinity and density‐dependent movement as indicators of fish habitat restoration efficacy

Polivka

2020

Ecosphere

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Conceptual and methodological tools from behavioral ecology can inform studies of habitat quality, and their potential for evaluating habitat restoration in conservation efforts is explored here. Such approaches provide mechanistic detail in understanding the relationship between organisms and their habitats and are thus more informative than correlations between density and habitat characteristics. Several Pacific salmon species have been the target of habitat restoration efforts for the past 2-3 decades, but most post-restoration effectiveness studies have been limited to correlative data described above. In mark-recapture assays from four different study years, the affinity of sub-yearling Chinook salmon (Oncorhynchus tschawytscha) and steelhead (O. mykiss) for stream pools restored with or created by engineered log structures was greater than that for pools without restoration, though with high interannual variability. From corresponding distribution and density data, it was clear that habitat affinity data are not always concordant with single observations of density. The same was true of the correlation between either affinity or density and physical characteristics of pools, although depth and current velocity had some explanatory power for both responses in Chinook. Movement into pools by Chinook during the assays indicated that restored pools can support more immigrants at a given density than can unrestored pools; however, no such pattern emerged for steelhead. Variation among individuals in body condition has implications for population-wide fitness, and such low variation was correlated with stronger affinity for pools in Chinook regardless of restoration status. This suggests that pools may mediate habitat-related trade-offs and that restoring them might have a positive effect on fitness. Thus affinity, immigration, and condition data give much-needed mechanistic indication of habitat selection for restored habitat via an apparent capacity increase and those potential fitness benefits. This is stronger support for restoration effectiveness than density differences alone because density data (1) may simply indicate redistribution of fish from poor to good habitats and (2) are not adequate to show correlations between restoration and positive change in traits correlated with fitness.

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Habitat affinity and density-dependent movement as indicators of fish habitat restoration efficacy

Polivka

2019

Preprint

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In mark-recapture assays from four different study years, the affinity of young-of-theyear Chinook Salmon (Oncorhynchus tschawytscha) and steelhead (O. mykiss) for stream pools restored with or created by engineered log structures was greater than that for pools without restoration, though with high interannual variability. From corresponding distribution and abundance data, it was clear that behavioral data are not always concordant with single observations of abundance. The same was true of the correlation between either behavior or abundance and physical characteristics of pools, although depth and current velocity had some explanatory power for both responses in Chinook. Density-dependent immigration into pools by Chinook indicated that restored pools have greater capacity for this species than unrestored pools; however no such pattern emerged for steelhead. Variation among individuals in body condition has implications for population-wide fitness and low variation was correlated with stronger affinity for pools. This suggests that pools mediate habitat-related trade-offs and that restoring them might have positive effects on fitness. Thus, behavioral data appear to provide stronger indications of restoration effectiveness than observational data alone.

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Responses to the Foraging/Predation Risk Trade-Off and Individual Variability in Population-Level Fitness Correlates

Cited by 5 publications

References 47 publications

Stream inflow and predation risk affect littoral habitat selection by benthic fish

Stream inflow and predation risk affect littoral habitat selection by benthic fish

Habitat affinity and density‐dependent movement as indicators of fish habitat restoration efficacy

Habitat affinity and density-dependent movement as indicators of fish habitat restoration efficacy

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