Population variation in density‐dependent growth, mortality and their trade‐off in a stream fish

Matte, Jean‐Michel; Fraser, Dylan J.; Grant, James W. A.

doi:10.1111/1365-2656.13124

Cited by 17 publications

(39 citation statements)

References 65 publications

(123 reference statements)

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“…As density increases, individual growth and/or survival typically decrease in fish (Rose et al, 2001; Sinclair, 1989). However, important variation exists across natural populations in the shape and strength of density‐dependent growth and survival, so that predicting these relationships is challenging (Matte, Fraser, & Grant, 2019; Rose et al, 2001). Understanding why different studies exhibit drastically different patterns of density dependence or independence is critical for the management of fisheries and endangered populations.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, they are socioeconomically important and are the target of numerous conservation and management efforts (Aas, Klemetsen, Einum, & Skurdal, 2010; Elliott, 1994). In salmonids, growth and survival can be density‐independent, but they most typically decrease with increasing density following one of three patterns: linear, logarithmic or exponential after habitat saturation (see Figure 1a; Grant & Imre, 2005; Matte et al, 2019; Post, Parkinson, & Johnston, 1999). While the strong variation in patterns of density‐dependent growth (Figure 1b) and survival (Figure 1c) in salmonids is unequivocal, there is little consensus as to the mechanisms behind this variation.…”

Section: Introductionmentioning

confidence: 99%

“…However, it is unclear whether comparing the shape of density‐dependent relationships across studies is appropriate, as they are conducted with different methodologies (e.g. conducted in the field or laboratory, or with different densities; Grant & Imre, 2005; Jenkins, Diehl, Kratz, & Cooper, 1999) and in different environments (Matte et al, 2019). To date, no review has quantified the relative importance of biological and methodological factors on the strength and shape of density‐dependent growth and survival across salmonid populations (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Environmental differences can partially explain population‐level variation in patterns of density‐dependent growth and survival in stream‐dwelling salmonids (Matte et al, 2019), but other biological factors may further complicate comparisons across studies. If food abundance is high, growth should be density‐independent but survival may decrease sharply after individuals saturate the available habitat (Grant & Kramer, 1990).…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, populations and/or species of salmonids could exhibit divergent reaction norms to density (Matte et al, 2019; Rose et al, 2001). These divergent reaction norms are possible given that different species and/or populations exhibit varying degrees of competitive abilities, territorial defence, and different foraging behaviour and life histories (Gunnarsson & Steingrímsson, 2011; Keenleyside, 1962; Rose et al, 2001; Tunney & Steingrímsson, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Density‐dependent growth and survival in salmonids: Quantifying biological mechanisms and methodological biases

2020

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Understanding the complex variation in patterns of density‐dependent individual growth and survival across populations is critical to adaptive fisheries management, but the extent to which this variation is caused by biological or methodological differences is unclear. Consequently, we conducted a correlational meta‐analysis of published literature to investigate the relative importance of methodological and biological predictors on the shape and strength of density‐dependent individual growth and survival in salmonids. We obtained 160 effect sizes from 75 studies of 12 species conducted between 1977 and 2019 that differed in experimental approach (sensu Ecological Monographs, 54, 187–211; 65 laboratory experiments, 60 observational field studies, and 35 field experiments). The experimental approach was the strongest factor influencing the strength of density dependence across studies: density‐dependent survival was stronger than growth in field observational studies, whereas laboratory experiments detected stronger density‐dependent growth than survival. The difference between density‐dependent growth and survival was minimal in field experiments, and between lotic and lentic habitats. The shape of density dependence (logarithmic, linear, exponential or density‐independent) could be predicted with 66.7% accuracy based solely on the experimental approach and the density gradient (highest/lowest*100) of the study. Overall, the strength and shape of density dependence were primarily influenced by methodological predictors, while biological factors (predator presence, food abundance, and species) had predictable but modest effects. For both empirical studies and adaptive fisheries management, we recommend using field experiments with a density gradient of at least 470% to detect the proper shape of the density‐dependent response, or accounting for potential biases if observational or laboratory studies are conducted.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Density‐dependent growth and survival in salmonids: Quantifying biological mechanisms and methodological biases

2020

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Microgeographic variation in demography and thermal regimes stabilize regional abundance of a widespread freshwater fish

Gallagher,

Fraser

2023

Ecological Applications

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Predicting the persistence of species under climate change is an increasingly important objective in ecological research and management. However, biotic and abiotic heterogeneity can drive asynchrony in population responses at small spatial scales, complicating species‐level assessments. For widely distributed species consisting of many fragmented populations, such as brook trout (Salvelinus fontinalis), understanding the drivers of asynchrony in population dynamics can improve the predictions of range‐wide climate impacts. We analyzed the demographic time series from mark–recapture surveys of 11 natural brook trout populations in eastern Canada over 13 years to examine the extent, drivers, and consequences of fine‐scale population variation. The focal populations were genetically differentiated, occupied a small area (~25 km2) with few human impacts, and experienced similar climate conditions. Recruitment was highly asynchronous, weakly related to climate variables and showed population‐specific relationships with other demographic processes, generating diverse population dynamics. In contrast, individual growth was mostly synchronized among populations and driven by a shared positive relationship with stream temperature. Outputs from population‐specific models were unrelated to four of the five hypothesized drivers (recruitment, growth, reproductive success, phylogenetic distance), but variation in groundwater inputs strongly influenced stream temperature regimes and stock–recruitment relationships. Finally, population asynchrony generated a portfolio effect that stabilized regional species abundance. Our results demonstrated that population demographics and habitat diversity at microgeographic scales can play a significant role in moderating species responses to climate change. Moreover, we suggest that the absence of human activities within study streams preserved natural habitat variation and contributed to asynchrony in brook trout abundance, while the small study area eased monitoring and increased the likelihood of detecting asynchrony. Therefore, anthropogenic habitat degradation, landscape context, and spatial scale must be considered when developing management strategies to monitor and maintain populations that are diverse, stable, and resilient to climate change.

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Mechanisms of density dependence in juvenile salmonids: prey depletion, interference competition, or energy expenditure?

Matte¹,

Fraser²,

Grant³

2021

Ecosphere

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Density dependence is a strong regulator of animal populations, operating primarily through intraspecific competition for a limiting resource. Because food is generally limited in natural environments, it is typically assumed that increasing animal density leads to reduced individual fitness through food depletion or monopolization. However, recent work demonstrates that density dependence can occur without apparent food depletion, or with virtually unlimited resources, suggesting that other mechanisms must also be important. Alternatively, density-dependent regulation could be achieved through increasing energy costs rather than decreasing food abundance. The relative importance of these two processes (food depletion and energy costs) and their underlying mechanisms remains unclear. Here, we manipulated the density of juvenile stream-dwelling brook trout (Salvelinus fontinalis) in three neighboring populations over two consecutive summers to relate food availability and consumption to density-dependent growth, survival, and their trade-off. Despite strong patterns of density dependence and evidence of food limitation, increasing fish density did not lead to detectable prey depletion in the environment. Instead, behavioral observations suggested that increasing densities resulted in higher energetic costs, primarily via increasing interference competition and the use of less suitable foraging microhabitats. These results highlight that animal populations may be regulated by density dependence without necessarily impacting prey communities.

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Population variation in density‐dependent growth, mortality and their trade‐off in a stream fish

Cited by 17 publications

References 65 publications

Density‐dependent growth and survival in salmonids: Quantifying biological mechanisms and methodological biases

Density‐dependent growth and survival in salmonids: Quantifying biological mechanisms and methodological biases

Microgeographic variation in demography and thermal regimes stabilize regional abundance of a widespread freshwater fish

Mechanisms of density dependence in juvenile salmonids: prey depletion, interference competition, or energy expenditure?

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