Density-dependent individual growth of marble trout (Salmo marmoratus) in the Soca and Idrijca river basins, Slovenia

Vincenzi, Simone; Crivellì, Alain J.; Jeseňsek, Dušan; Rubin, Jean‐François; Leo, Giulio A. De

doi:10.1007/s10750-006-0470-z

Cited by 20 publications

(26 citation statements)

References 49 publications

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“…Two of the stocks developed clear bimodal length-frequency distributions, whereas the other two stocks displayed skewed or weakly bimodal length-frequency distributions. Vincenzi et al (2007b) did not observe polymodality in the length-frequency distribution of marble trout, and our analysis suggests that episodes of massive mortality may contribute to the observed pattern, since all marble trout populations living in Slovenian streams are impacted by flood events. We predict that in populations which are adapted to stream environments that are not subject to flood events, multi-modality of the length-frequency distribution may be observed.…”

Section: Discussionsupporting

confidence: 42%

Selective consequences of catastrophes for growth rates in a stream-dwelling salmonid

et al. 2011

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Optimal life histories in a fluctuating environment are likely to differ from those that are optimal in a constant environment, but we have little understanding of the consequences of bounded fluctuations versus episodic massive mortality events. Catastrophic disturbances, such as floods, droughts, landslides and fires, substantially alter the population dynamics of affected populations, but little has been done to investigate how catastrophes may act as a selective agent for life-history traits. We use an individual-based model of population dynamics of the stream-dwelling salmonid marble trout (Salmo marmoratus) to investigate how trade-offs between the growth and mortality of individuals and density-dependent body growth can lead to the maintenance of a wide or narrow range of individual variation in body growth rates in environments that are constant (i.e., only demographic stochasticity), variable (i.e., environmental stochasticity), or variable with catastrophic events that cause massive mortalities (e.g., flash floods). We find that occasional episodes of massive mortality can substantially reduce persistent variability in individual growth rates. Lowering the population density reduces density dependence and allows for higher fitness of more opportunistic strategies (rapid growth and early maturation) during the recovery period.

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Section: Discussionsupporting

confidence: 42%

Selective consequences of catastrophes for growth rates in a stream-dwelling salmonid

et al. 2011

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“…age-specific survival, body-size growth rates and the relationship between female length and fecundity (Vincenzi et al 2007a(Vincenzi et al , b, 2008. We also observed density-dependent patterns in marble trout for both individual growth (Vincenzi et al 2007b) and firstyear survival (Vincenzi et al 2007a). Here, we report our individual-based model of marble trout population dynamics which we developed based on marble trout population parameters and empirical models of densitydependent processes (Vincenzi et al 2007a(Vincenzi et al , b, 2008.…”

Section: Introductionmentioning

confidence: 52%

“…is the maximum length (mm), k is the Brody's growth coefficient relating age to length and x 0 (years) is the age at which length equals 0. The growth curve parameters for both Gorska and Zakojska marble trout populations were estimated separately by pooling together age-length data from different years (Vincenzi et al 2007b) (Table 1). However, Vincenzi et al (2007b) found evidence of density-dependent individual growth in the newly introduced marble trout populations.…”

Section: Density-dependent Individual Growthmentioning

confidence: 99%

“…The growth curve parameters for both Gorska and Zakojska marble trout populations were estimated separately by pooling together age-length data from different years (Vincenzi et al 2007b) (Table 1). However, Vincenzi et al (2007b) found evidence of density-dependent individual growth in the newly introduced marble trout populations. A number of factors have been suggested to explain the phenomenon of density-dependent growth in freshwater salmonids; these range from overcrowding to low food availability and thus constrained feeding rates (Klemetsen et al 2003) and increased defence costs (Hixon 1980).…”

Section: Density-dependent Individual Growthmentioning

confidence: 99%

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The role of density-dependent individual growth in the persistence of freshwater salmonid populations

Vincenzi

Crivellì

Jeseňsek³

et al. 2008

Oecologia

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Theoretical and empirical models of populations dynamics have paid little attention to the implications of density-dependent individual growth on the persistence and regulation of small freshwater salmonid populations. We have therefore designed a study aimed at testing our hypothesis that density-dependent individual growth is a process that enhances population recovery and reduces extinction risk in salmonid populations in a variable environment subject to disturbance events. This hypothesis was tested in two newly introduced marble trout (Salmo marmoratus) populations living in Slovenian streams (Zakojska and Gorska) subject to severe autumn floods. We developed a discrete-time stochastic individual-based model of population dynamics for each population with demographic parameters and compensatory responses tightly calibrated on data from individually tagged marble trout. The occurrence of severe flood events causing population collapses was explicitly accounted for in the model. We used the model in a population viability analysis setting to estimate the quasi-extinction risk and demographic indexes of the two marble trout populations when individual growth was density-dependent. We ran a set of simulations in which the effect of floods on population abundance was explicitly accounted for and another set of simulations in which flood events were not included in the model. These simulation results were compared with those of scenarios in which individual growth was modelled with density-independent Von Bertalanffy growth curves. Our results show how density-dependent individual growth may confer remarkable resilience to marble trout populations in case of major flood events. The resilience to flood events shown by the simulation results can be explained by the increase in size-dependent fecundity as a consequence of the drop in population size after a severe flood, which allows the population to quickly recover to the pre-event conditions. Our results suggest that density-dependent individual growth plays a potentially powerful role in the persistence of freshwater salmonids living in streams subject to recurrent yet unpredictable flood events.

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“…In contrast, a 10-fold decrease in population density, either through reduced stocking density or increased loss (the slope estimates are nearly identical), is predicted to yield a twofold increase in mean body mass. Using a large-scale manipulation in natural streams enabled this closer look at the drivers underlying the extreme spatial variation in juvenile Atlantic salmon growth in the field, expanding beyond previous observational (Crisp 1993;Newman 1993;Imre et al 2005;Lobon-Cervia 2007;Vincenzi et al 2007) and experimental (Jenkins et al 1999;Bohlin et al 2002;Einum et al 2006) studies reporting densitydependent growth of salmon and trout in natural streams. Here, we review the potential limitations of this result and implications for Atlantic salmon populations and stream fisheries management.…”

Section: Discussionmentioning

confidence: 99%

Increased Population Density and Suppressed Prey Biomass: Relative Impacts on Juvenile Atlantic Salmon Growth

Ward¹,

Nislow

Folt³

2009

Trans Am Fish Soc

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Individual growth rates of fish often depend on both population density and resource availability, both of which are subject to anthropogenic impacts and can be manipulated in the interest of restoring or enhancing fish populations. However, direct tests of the relative contribution of these factors to growth variation are lacking for most populations and are critically needed to guide management. We used a large‐scale field experiment to evaluate the relative effects of increased population density and suppressed prey biomass on the growth of juvenile Atlantic salmon Salmo salar. We directly manipulated salmon population density by releasing newly hatched salmon fry from uniform initial conditions at three density treatments in natural streams (18 sites total, repeated over 2 years). We arrayed the density treatments across sites that encompassed a more than 10‐fold range in the biomass of benthic invertebrate prey for salmon, a low prey biomass being associated with heavy shading from riparian forest canopy. This controlled approach clearly demonstrated the enormous growth plasticity of juvenile Atlantic salmon; their mean body mass ranging from 1.2 to 14 g across sites after one growing season. Variation in prey biomass had the strongest effects on fish growth. The fish grew faster at sites with high prey biomass regardless of population density, and prey biomass alone accounted for 71% of the explained variation in their growth. Only after taking the variation explained by prey biomass into account was it apparent that the study fish grew faster at sites with low stocking density and at sites where high losses reduced Atlantic salmon population density. To maintain salmon growth and size‐dependent life histories, restoration and management efforts clearly need to consider anthropogenic factors that suppress prey abundance.

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Density-dependent individual growth of marble trout (Salmo marmoratus) in the Soca and Idrijca river basins, Slovenia

Cited by 20 publications

References 49 publications

Selective consequences of catastrophes for growth rates in a stream-dwelling salmonid

Selective consequences of catastrophes for growth rates in a stream-dwelling salmonid

The role of density-dependent individual growth in the persistence of freshwater salmonid populations

Increased Population Density and Suppressed Prey Biomass: Relative Impacts on Juvenile Atlantic Salmon Growth

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