Tolmin Angling Association

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Tolmin Angling Association

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Vincenzi S.,University of California at Santa Cruz | Vincenzi S.,Southwest Fisheries Science Center | Mangel M.,University of California at Santa Cruz | Mangel M.,University of Bergen | And 3 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2017

Climate change is predicted to increase the frequency and intensity of extreme climate events. Tests on empirical data of theory-based predictions on the consequences of extreme climate events are thus necessary to understand the adaptive potential of species and the overarching risks associated with all aspects of climate change. We tested predictions on the genetic and life-history consequences of extreme climate events in two populations of marble trout Salmo marmoratus that have experienced severe demographic bottlenecks due to flash floods. We combined long-term field and genotyping data with pedigree reconstruction in a theory-based framework. Our results show that after flash floods, reproduction occurred at a younger age in one population. In both populations, we found the highest reproductive variance in the first cohort born after the floods due to a combination of fewer parents and higher early survival of offspring. A small number of parents allowed for demographic recovery after the floods, but the genetic bottleneck further reduced genetic diversity in both populations. Our results also elucidate some of the mechanisms responsible for a greater prevalence of faster life histories after the extreme event. © 2017 The Author(s) Published by the Royal Society. All rights reserved.


Simcic T.,Slovenian National Institute of Biology | Jesensek D.,Tolmin Angling Association | Brancelj A.,Slovenian National Institute of Biology
Fish Physiology and Biochemistry | Year: 2015

Climate change may result in future alterations in thermal regime which could markedly affect the early developmental stages of cold water fish due to their expected high sensitivity to increasing temperature. In the present study, the effect of temperature increase of 2, 4 and 6 °C on the oxygen consumption rate (R), the activity of respiratory electron transport system (ETS) and oxidative stress have been studied in four developmental stages of the marble trout (Salmo marmoratus)—eyed eggs, yolk-sac larvae and juveniles of 1 and 3 months. Oxygen consumption rate and ETS activity increased with level of development and with temperature in all four stages. ETS/R ratios decreased during development and correlated with temperature in eyed eggs, larvae and juveniles of 1 month, but not in juveniles of 3 months. Low ETS/R ratios at higher temperatures indicate stress response in eyed eggs, the most temperature sensitive developmental stage. Catalase (CAT) and glutathione reductase (GR) activities increased during development, but responded differently to elevated temperature in the different developmental stages. Stress in eyed eggs, caused by higher temperatures, resulted in increased oxygen consumption rate and increased activities of CAT and GR. Larvae were sensitive to increased temperature only at the highest experimental temperature of 16 °C. Increased temperature did not stress the metabolism of the juveniles, since they were able to compensate their metabolic activity. The earlier developmental stages of marble trout are thus more sensitive to temperature increase than juveniles and therefore more endangered by higher water temperatures. This is the first report connecting oxygen consumption, ETS activity and ETS/R ratio with the activities of antioxidant enzymes in relation to increased temperature in salmonids. © 2015, Springer Science+Business Media Dordrecht.


Simcic T.,Slovenian National Institute of Biology | Jesensek D.,Tolmin Angling Association | Brancelj A.,Slovenian National Institute of Biology
Turkish Journal of Fisheries and Aquatic Sciences | Year: 2015

The size and composition of fish eggs are related to female’s characteristics, such as age, size and individual conditions, and they have an impact on the properties of offspring that are important for their fitness. Electron transport system (ETS) activity and respiration rate (R) of early life history stages (i.e. non-fertilized eggs, eggs at eyed stage and larvae with yolk sac) of 13 females of marble trout (Salmo marmoratus) were measured separately in order to determine their metabolic properties in relation to size. The results showed that larger females produced larger eggs in higher numbers. Growth experiments on the survival of offspring of a single female revealed that the survival rate of early embryos was higher for smaller eggs during the earliest stages, but ultimately the percentage of surviving larvae did not correlate with egg size. The ETS activities and respiration rates of non-fertilized eggs, eyed eggs and larvae differed significantly between 13 females. Both parameters increased with increasing dry mass of the early life history stages, but the increase of respiration rate was greater than that of ETS activity. The lower ETS/R ratios in larger individuals therefore indicate that their energy metabolism was less adaptable to environmental changes than that of smaller ones. Larger egg size could be an advantage under favourable conditions, whereas smaller size could be optimal under stressing circumstances in which the higher metabolic potential enables production of the energy required for metabolism. This is first report on the relationship between ETS activity and respiration rate of the early life history stages in salmonids. © Published by Central Fisheries Research Institute (CFRI) Trabzon, Turkey.


Vincenzi S.,University of California at Santa Cruz | Vincenzi S.,Polytechnic of Milan | Mangel M.,University of California at Santa Cruz | Mangel M.,University of Bergen | And 3 more authors.
Ecological Applications | Year: 2016

Understanding the causes of within-and among-population differences in vital rates, life histories, and population dynamics is a central topic in ecology. To understand how within-and among-population variation emerges, we need long-term studies that include episodic events and contrasting environmental conditions, data to characterize individual and shared variation, and statistical models that can tease apart shared and individual contribution to the observed variation. We used long-term tag-recapture data to investigate and estimate within-and among-population differences in vital rates, life histories, and population dynamics of marble trout Salmo marmoratus, an endemic freshwater salmonid with a narrow range. Only ten populations of pure marble trout persist in headwaters of Alpine rivers in western Slovenia. Marble trout populations are also threatened by floods and landslides, which have already caused the extinction of two populations in recent years. We estimated and determined causes of variation in growth, survival, and recruitment both within and among populations, and evaluated trade-offs between them. Specifically, we estimated the responses of these traits to variation in water temperature, density, sex, early life conditions, and extreme events. We found that the effects of population density on traits were mostly limited to the early stages of life and that growth trajectories were established early in life. We found no clear effects of water temperature on vital rates. Population density varied over time, with flash floods and debris flows causing massive mortalities (>55% decrease in survival with respect to years with no floods) and threatening population persistence. Apart from flood events, variation in population density within streams was largely determined by variation in recruitment, with survival of older fish being relatively constant over time within populations, but substantially different among populations. Marble trout show a fast to slow continuum of life histories, with slow growth associated with higher survival at the population level, possibly determined by food conditions and age at maturity. Our work provides unprecedented insight into the causes of variation in vital rates, life histories, and population dynamics in an endemic species that is teetering on the edge of extinction. © 2016 by the Ecological Society of America.


Musseau C.,University Paul Sabatier | Musseau C.,Ecolab | Vincenzi S.,University of California at Santa Barbara | Vincenzi S.,Polytechnic of Milan | And 8 more authors.
Ecosphere | Year: 2015

Dietary plasticity of populations can be associated to ontogenetic diet preferences and depends on the size-structure of populations. Dietary niche characterizes the functional role of organisms in a food web, as it reflects both resources' diversity used by a consumer and trophic interactions in the system. Dietary niches are controlled both by biotic and abiotic factors, but their interactions in natural systems remain poorly studied. Here, we investigated the variability of dietary niche in salmonid wild populations focusing both on inter-population and intra-population (through time) trophic changes, using marble trout (Salmo marmoratus) living in Slovenian headwater streams as a model system. Stable isotope analysis showed high variability of dietary niche and trophic diversity among six of the seven remnant marble trout populations. We observed substantial differences in dietary niche width among populations and within populations through time. Results of partial least square path modelling highlighted opposite effects of immature and mature trout on trophic niche structure. Direct effects of temperature and slope (stream and watershed) were opposite; temperature narrowed dietary niches while slope increased them. Environmental factors (e.g., temperature, stream and watershed slope) had indirect effects on trophic niches after accounting for fish density. Our results showed that size-distribution and sexual maturity are key determinants of the dietary niche width in a population. Increasing density of immature trout tended to widen the dietary niche while increasing density of mature trout tended to narrow it. Environmental factors had direct effects both on resources and consumers densities and indirect effects. Direct and indirect effects were often antagonistic. © 2015 Musseau et al.


Pujolar J.M.,University of Padua | Vincenzi S.,University of Parma | Zane L.,University of Padua | Jesensek D.,Tolmin Angling Association | And 2 more authors.
PLoS ONE | Year: 2011

A changing global climate can threaten the diversity of species and ecosystems. We explore the consequences of catastrophic disturbances in determining the evolutionary and demographic histories of secluded marble trout populations in Slovenian streams subjected to weather extremes, in particular recurrent flash floods and debris flows causing massive mortalities. Using microsatellite data, a pattern of extreme genetic differentiation was found among populations (global F ST of 0.716), which exceeds the highest values reported in freshwater fish. All locations showed low levels of genetic diversity as evidenced by low heterozygosities and a mean of only 2 alleles per locus, with few or no rare alleles. Many loci showed a discontinuous allele distribution, with missing alleles across the allele size range, suggestive of a population contraction. Accordingly, bottleneck episodes were inferred for all samples with a reduction in population size of 3-4 orders of magnitude. The reduced level of genetic diversity observed in all populations implies a strong impact of genetic drift, and suggests that along with limited gene flow, genetic differentiation might have been exacerbated by recurrent mortalities likely caused by flash flood and debris flows. Due to its low evolutionary potential the species might fail to cope with an intensification and altered frequency of flash flood events predicted to occur with climate change. © 2011 Pujolar et al.


Vincenzi S.,University of Parma | Crivelli A.J.,Station Biologique de la Tour du Valat | Jesensek D.,Tolmin Angling Association | De Leo G.A.,University of Parma
Ecology of Freshwater Fish | Year: 2010

Density-dependent body growth has often been observed in freshwater salmonid populations. Several studies suggest this compensatory pattern as a potential mechanism of population regulation. The choice of the spatial scale is important for the detection of density-dependent growth, as study areas need to be of the appropriate size to capture the density of conspecifics actually experienced by individuals over the preceding growth period. Here, we used four marble trout (Salmo marmoratus) populations (Gatsnik, Gorska, Huda and Zakojska) living in Slovenian stream to study the relationships between early density of marble trout and subsequent body growth. As streams are divided in sectors delimited by natural barriers that prevent or strongly limit movement of individuals, we tested the relationship between early density and body size through the lifetime at two spatial scales, that is, sector level (for Gatsnik and Zakojska) and whole stream level (the four populations were pooled). Sector length in Gatsnik and Zakojska ranged from 113 to 516 m. At both sector and whole stream level, temporal data were pooled. Growth declined significantly with increasing density both at the sector and whole stream levels, and the density-dependent relationship was described by negative power curves. However, at the sector level the density-dependent pattern was stronger in Gatsnik, a stream in which fish could move across sectors, than in Zakojska, where upstream movement across sectors is prevented by waterfalls. © 2010 John Wiley & Sons A/S.


Vincenzi S.,University of Parma | Crivelli A.J.,Station Biologique de la Tour du Valat | Jesensek D.,Tolmin Angling Association | De Leo G.A.,University of Parma
Ecology of Freshwater Fish | Year: 2010

The role of density-dependent individual growth in the recruitment dynamics of fish populations has rarely been analysed in a quantitative framework. Variations of mean size of juveniles in response to changes in population densities have frequently been observed in salmonids and it has been shown that body-size differences at the juvenile stage can persist through the sub-adult and adult stage. As fecundity and sexual maturation are often a function of body size, inter-cohort variations in individual growth may ultimately affect the reproductive output and, consequently, the amount of yearly recruitment. Here, we present a simulation analysis investigating the effects of density-dependent growth on the reproductive output and, ultimately, on the population dynamics of stream-dwelling salmonids. The demographic model used for the numerical analysis was parameterised using marble trout Salmo marmoratus as a reference species and explicitly accounted for the occurrence of major floods events causing the population to collapse to very low densities. Our simulations showed that density-dependent individual growth is a powerful mechanism to foster population resilience through compensatory recruitment. In addition, we argue that density-dependent growth also helps regulate recruitment at high population densities. We show that even slight variations in the growth trajectories of fish substantially affect the size and the dynamics of the population. © 2010 John Wiley & Sons A/S.


Vincenzi S.,University of California at Santa Cruz | Crivelli A.J.,Station Biologique de la Tour du Valat | Jesensek D.,Tolmin Angling Association | de Leo G.A.,University of Parma
Reviews in Fish Biology and Fisheries | Year: 2012

Translocation programs are a common strategy to increase the number of viable populations of threatened freshwater fishes. Yet, only in a minority of cases the success or failure of translocations has been assessed through a quantitative analysis of demographic traits, compensatory responses, life-histories and population dynamics of the threatened species. A paradigmatic case a translocation program combining both management- and research-oriented activities is represented by the Marble Trout Conservation Program, which started in 1993 in the upper reaches of the Soca, Idirjca and Baca river basins (Slovenia) for the conservation of stream-dwelling marble trout Salmo marmoratus. In order to enhance the viability of the species, two new populations were created in 1996 by stocking 500 marble trout aged 1+ in previously fishless streams (Gorska and Zakojska) within the core habitat of the species. The new populations have been systematically monitored for 15 years by individually tagging and sampling marble trout. Our analyses show that deterministic extinction of marble trout populations are unlikely and that high-magnitude environmental stochasticity (i.e., severe floods) is the only main cause of local population extinction, despite the high resilience to flood-induced massive mortalities exhibited by marble trout through compensatory mechanisms (e.g., relaxation of density-dependent body growth and survival at low densities). Fishless headwaters, probably characterized by a history of recurrent severe floods, should not be considered as candidate sites for the creation of new populations. Fewer individuals than originally reintroduced (i.e., 500 fish aged 1+ in each stream) might be sufficient to establish viable populations, since compensatory mechanisms are likely to regulate population size around stream carrying capacity in a few years. Besides enhancing the species viability, translocation programs can provide an excellent framework for the estimation of ecological traits (e.g., life-histories, demography, population dynamics etc.), identify potential vulnerabilities and thus guide well-formed management actions for the threatened species. © 2011 Springer Science+Business Media B.V.


Vincenzi S.,University of Parma | Crivelli A.J.,Station Biologique de la Tour du Valat | Jesensek D.,Tolmin Angling Association | Rossi G.,University of Parma | De Leo G.A.,University of Parma
Naturwissenschaften | Year: 2011

To understand the consequences of the invasion of the nonnative rainbow trout Oncorhynchus mykiss on the native marble trout Salmo marmoratus, we compared two distinct headwater sectors where marble trout occur in allopatry (MTa) or sympatry (MTs) with rainbow trout (RTs) in the Idrijca River (Slovenia). Using data from field surveys from 2002 to 2009, with biannual (June and September) sampling and tagging from June 2004 onwards, we analyzed body growth and survival probabilities of marble trout in each stream sector. Density of age-0 in September over the study period was greater for MTs than MTa and very similar between MTs and RTs, while density of trout ≥age-1 was similar for MTa and MTs and greater than density of RTs. Monthly apparent survival probabilities were slightly higher in MTa than in MTs, while RTs showed a lower survival than MTs. Mean weight of marble and rainbow trout aged 0+ in September was negatively related to cohort density for both marble and rainbow trout, but the relationship was not significantly different between MTs and MTa. No clear depression of body growth of sympatric marble trout between sampling intervals was observed. Despite a later emergence, mean weight of RTs cohorts at age 0+ in September was significantly higher than weight of both MTs and MTa. The establishment of a self-sustaining population of rainbow trout does not have a significant impact on body growth and survival probabilities of sympatric marble trout. The numerical dominance of rainbow trout in streams at lower altitudes seem to suggest that while the low summer flow pattern of Slovenian streams is favorable for rainbow trout invasion, the adaptation of marble trout to headwater environments may limit the invasion success of rainbow trout in headwaters. © 2010 Springer-Verlag.

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