Leif Asbjørn Vøllestad

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• PhD
• Professor (Full) at University of Oslo

Selective harvest of large individuals should alter natural adaptive landscapes and drive evolution toward reduced somatic growth and increased reproductive investment. However, few studies have simultaneously considered the relative importance of artificial and natural selection in driving trait changes in wild populations. Using 50 years of indiv...

Migrations between different habitats are key events in the lives of many organisms. Such movements involve annually recurring travel over long distances usually triggered by seasonal changes in the environment. Often, the migration is associated with travel to or from reproduction areas to regions of growth. Young anadromous Atlantic salmon (Salmo...

There is an increasing concern about the potential for size-selective harvest to impair population persistence. Yet little is known about the relative contribution of the evolutionary (shifts in life history) and demographic effects (decreased population density and size truncation) of harvesting to changes in fitness. Using medaka (Oryzias latipes...

Anguillid eels were once considered to be the classic example of catadromy. However, alternative life cycles have been reported, including skipping the freshwater phase and habitat shifting between fresh, brackish, and saltwater throughout the growth phase. There is a lack of knowledge regarding these alternate life strategies, for example, the pr...

Managers and stakeholders increasingly ask whether predation is a driving force behind the poor status of many species, and whether predator control is likely to be a successful management action to intervene. We review existing literature on Atlantic salmon Salmo salar predation and predator control, as well as general ecological theory on the rol...

We present haplotype-resolved whole-genome assemblies from one individual European river lamprey (Lampetra fluviatilis) and one individual brook lamprey (Lampetra planeri), usually regarded as sister species. The genome assembly of L. fluviatilis consists of pseudo-haplotype one, spanning 1073 Mb and pseudo-haplotype two, spanning 963 Mb. Likewise...

The Norwegian freshwater fish fauna is depauperate, containing 32 naturally occurring species. Knowledge about the distribution of some of these species is still limited. We used eDNA for mapping the local distribution of freshwater fish in rivers and streams in the Haldenvassdraget watercourse. A total of 45 locations were sampled during June 2021...

We present haplotype-resolved whole-genome assemblies from two individuals of the sister species the European river lamprey (Lampetra fluviatilis) and the brook lamprey (Lampetra planeri). The genome assemblies for L. fluviatilis consists of pseudo-haplotype one, spanning 1073 megabases and 963 megabases for pseudo-haplotype two. For L. planeri, th...

It is increasingly recognised that ecology and evolution may interact on contemporary time scales and result in ongoing eco-evolutionary dynamics at population- community- and ecosystem levels. Therefore, an eco-evolutionary perspective is needed to better understand how fish populations may respond to ongoing and future climate change. This chapte...

The fishes are an extremely diverse and interesting group of vertebrates, and provide protein and joy to humans throughout the globe. When I was asked if I could write an essay about my career as a fish ecologist my first thought was: what is there to write about? After some thought I decided to give it a try. I describe how I ended up studying fis...

Hydropower (HP) has become the most important renewable energy source worldwide during the last century. However, the impacts on aquatic ecosystems may be considerable. In the Northern Hemisphere, salmonid fishes are often affected by hydropower‐related temperature alterations. As their metabolic processes are entirely dependent on water temperatur...

Climate change is anticipated to cause species to shift their ranges upward and poleward, yet space for tracking suitable habitat conditions may be limited for range‐restricted species at the highest elevations and latitudes of the globe. Consequently, range‐restricted species inhabiting Arctic freshwater ecosystems, where global warming is most pr...

The state of sea trout in 1251 Norwegian watercourses was assessed based on a scoring system for human pressures, abundance data, and local knowledge. Over 16,000 km of rivers and lakes were available to sea trout in these watercourses, spanning from the temperate to Arctic regions. Sea trout were classified to be in a good or very good state in fe...

Brown trout Salmo trutta populations are common in small boreal streams in Scandinavia. Populations are often small and isolated. In this chapter, I summarized studies conducted for 8 years on a population of small-sized brown trout living in a small Norwegian boreal stream exposed to harsh winters (>5 months of ice cover) and low water levels duri...

Incidental capture of non-target species by fisheries, also referred to as bycatch, is a major concern for the management of marine megafauna species. In Norway, it has been estimated that 555 harbor seals (Phoca vitulina) get entangled and drown in gillnets every year. The majority of these bycatch events occur in large-mesh gillnet fisheries targ...

Unravelling evolution-by-environment interactions on the gut microbiome is particularly relevant considering the unprecedented level of human-driven disruption of the ecological and evolution- ary trajectories of species. Here, we aimed to evaluate whether an evolutionary response to size- selective mortality influences the gut microbiome of medaka...

The knowledge about freshwater fish in Norway is limited. Does it matter? Norwegian freshwaters contain relatively few fish species. The different species are also very differently distributed. To properly manage and conserve this resource, knowledge on the species´ ecology is needed. Here, I summarize the published research on the 44 reported fres...

Brown trout (Salmo trutta L. 1758) and Arctic charr [Salvelinus alpinus (L. 1758)] tagged with acoustic transmitters migrated from fresh water to the sea mainly in May and June, but with large individual variation in migration timing. For S. trutta, large individuals (42–86 cm total length) migrated earlier in the season than small individuals (18–...

Norwegian freshwater systems are in general species poor. That is particularly the case for the freshwater fishes. Only 32 species are considered native, whereas an additional 12 species are non-native. Some of the non-native species are also considered to be invasive and have negative ecosystem effects. Freshwater fishes are exposed to numerous st...

Gut microbiome diversity and functions are jointly shaped by the host's genetic background and environmental conditions, but the consequences of this interaction are still unclear. Unravelling the effect of the interaction between evolution and environment on the gut microbiome is particularly relevant considering the unprecedented level of human-d...

Many anguillid eel species display facultative catadromy. Some eel spend their entire life cycle in marine coastal areas, but the geographical extent of this, especially at the extremes of their distributional ranges, is unknown. We analysed otolith Sr:Ca and Ba:Ca from yellow-stage European eel (Anguilla anguilla) sampled along the coast of Norway...

Saltwater and freshwater environments have opposing physiological challenges, yet, there are fish species that are able to enter both habitats during short time spans, and as individuals they must therefore adjust quickly to osmoregulatory contrasts. In this study, we conducted an experiment to test for plastic responses to abrupt salinity changes...

Saltwater- and freshwater environments have opposing physiological challenges, yet, there are fish species that are able to enter both habitats during short time-spans, and as individuals they must therefore adjust quickly to osmoregulatory contrasts. In this study, we conducted an experiment to test for plastic responses to abrupt sainity changes...

L'Abée-Lund J.H., Lo H. and Vøllestad L.A. 2022: Diel variation in activity and feeding in sympatric brown trout (Salmo trutta) and Arctic char (Salvelinus alpinus) throughout the ice-free season in a Nor-wegian lake. Boreal Env. Res. 27: 117-130. Most animals are active during distinct diel periods. Salmonid fishes may shift from being mostly diur...

Knowledge of the three‐dimensional behavior and activity patterns of mesopelagic fishes is crucial for understanding their role in ecological and biogeochemical processes in the ocean. We here show that the use of submerged stationary echosounders enables detailed analysis of three‐dimensional swimming behavior of small mesopelagic fishes in situ....

For species with individual variation in reproductive success, experience in breeding and the distribution of different breeders is important for population productivity and viability. Human impacts, such as climate change and harvesting, can alter this distribution and thus population dynamics. Here, we investigated the effect of spawning experience...

Freshwater species are particularly vulnerable to emerging threats linked to climate change because they are often already heavily impacted by habitat destruction, pollution, and exploitation. For many harvested populations of freshwater fish, these combined impacts have been mitigated for decades through stocking with captive-bred individuals. How...

Size-selective mortality due to harvesting is a threat to numerous exploited species, but how it affects the ecosystem remains largely unexplored. Here, we used a pond mesocosm experiment to assess how evolutionary responses to opposite size-selective mortality interacted with the environment (fish density and light intensity used as a proxy of res...

The movement patterns of three commercially important wrasse (Labridae) species inside a small marine protected area (~ 0.15 km²) on the west coast of Norway were analysed over a period of 21 months. The mean distance between capture and recapture locations varied between 10 and 187 m, and was species and season specific. The extent of movement was...

Long-term observations of ice phenology in lakes are ideal for studying climatic variation in time and space. We used a large set of observations from 1890 to 2020 of the timing of freeze-up and break-up, and the length of ice-free season, for 101 Norwegian lakes to elucidate variation in ice phenology across time and space. The dataset of Norwegia...

Freshwater acidification is characterised by elevated concentrations of aqueous aluminium. Global emissions of acidifying agents are reduced due to international agreements, and freshwater acidification has shifted from chronic to a more episodic character. The recovery of fish populations in acidified areas is likely to depend on the individual’s...

Otoliths are inner‐ear structures of all teleost fish with functional importance for hearing and balance. The otoliths usually consist of aragonite, a polymorph of calcium carbonate, but may also take the form partly or entirely of vaterite, a different polymorph of calcium carbonate. Vateritic otoliths occur sporadically in wild fish, but with a h...

Understanding how populations are structured in space and time is a central question in evolutionary biology. Parasites and their hosts are assumed to evolve together, however, detailed understanding of mechanisms leading to genetic structuring of parasites and their hosts are lacking. As a parasite depends on its host, studying the genetic structu...

Long-term observations of ice phenology in lakes are ideal for studying climatic variation in time and space. We used a large set of observations from 1890 to 2020 of the timing of freeze-up and break-up, and the length of ice-free season, for 101 Norwegian lakes to elucidate variation in ice phenology across time and space. The dataset of Norwegia...

Background Earlier breeding is one of the strongest responses to global change in birds and is a key factor determining reproductive success. In most studies of climate effects, the focus has been on large-scale environmental indices or temperature averaged over large geographical areas, neglecting that animals are affected by the local conditions...

Exploring microbial communities using joint molecular approaches such as CARD-FISH and 16S sequencing.

Freshwater colonization by threespine stickleback has led to divergence in morphology between ancestral marine and derived freshwater populations, making them ideal for studying natural selection on phenotypes. In an open brackish–freshwater system, we previously discovered two genetically distinct stickleback populations that also differ in geomet...

Ecological and evolutionary effects of environmental variation on wild populations are of particular interest in a changing world. Large-scale environmental indices are classically used as environmental explanatory variables to study climate change effects on wild populations. However, these measures neglect the fact that individuals are affected b...

Temperature is a key environmental parameter affecting both the phenotypes and distributions of organisms, particularly ectotherms. Rapid organismal responses to thermal environmental changes have been described for several ectotherms; however, the underlying molecular mechanisms often remain unclear. Here, we studied whole genome cytosine methylat...

Evidence‐based management of natural populations under strong human influence frequently requires not only estimates of survival but also knowledge about how much mortality is due to anthropogenic vs. natural causes. This is the case particularly when individuals vary in their vulnerability to different causes of mortality due to traits, life histo...

Background: Long-term data from marked animals provide a wealth of opportunities for studies with high relevance to both basic ecological understanding and successful management in a changing world. The key strength of such data is that they allow us to quantify individual variation in vital rates (e.g. survival, growth, reproduction) and then lin...

Marine protected areas (MPAs) are increasingly implemented worldwide to maintain and restore depleted populations. However, despite our knowledge on the myriad of positive responses to protection, there are few empirical studies on the ability to conserve species’ mating patterns and secondary sexual traits. In male European lobsters (Homarus gamma...

The European eel (Anguilla anguilla) is critically endangered throughout its range. Knowledge about age distribution of future spawners (silver eels) is essential to monitor the status and contribute to the recovery of this species. Determination of age in anguillid eels is challenging, especially in eels from the northern part of the distribution...

The determinants of intraspecific stoichiometric variation remain difficult to elucidate due to their multiple origins (e.g. genetic vs. environmental) and potential interactive effects. We evaluated whether two size-selected lines of medaka (Oryzias latipes) with contrasted life-history strategies (small- and large-breeder lines with slow growth a...

Background: Studying variation in life-history traits and correlated behaviours, such as boldness and foraging (i.e., pace-of-life syndrome), allows us to better understand how these traits evolve in a changing environment. In fish, it is particularly relevant studying the interplay of resource abundance and size-selection. These are two environme...

Linking ecology and evolution can be challenging, particularly as these fields evolve rapidly tracking technological and theoretical developments. Thus, it is important for practitioners of different biological disciplines to understand new opportunities and challenges. Since theory and methods evolve, so will research programmes—often tracking opp...

Abstract Harvesting is often size‐selective, and in species with sexual size dimorphism, it may also be sex‐selective. A powerful approach to investigate potential consequences of size‐ and/or sex‐selective harvesting is to simulate it in a demographic population model. We developed a population‐based integral projection model for a size‐ and sex‐s...

Trout are one of the most culturally, economically, and ecologically important taxonomic groups of freshwater fishes worldwide. Native to all continents in the Northern Hemisphere, trout belong to seven genera, which are distributed across 52 countries. Despite their broad importance as societal icons and as indicators of biodiversity, many of the...

1. Humans are influencing animal and plant populations both directly (e.g.through harvest) and indirectly by altering environments. For many exploitedspecies, stocking with captive-bred individuals is a common strategy tomitigate negative human impacts and sustain populations over time. However,accumulating knowledge of negative side effects of sto...

Salmonids represent an intriguing taxonomical group for investigating genome evolution in vertebrates due to their relatively recent last common whole genome duplication event, which occurred between 80 and 100 million years ago. Here, we report on the chromosome-level genome assembly of European grayling (Thymallus thymallus), which represents one...

Background Long-term data from marked animals provide a wealth of opportunities for studies with high relevance to both basic ecological understanding and successful management in a changing world. The key strength of such data is that they allow to quantify individual variation in vital rates (e.g. survival, growth, reproduction) and then link it...

Evidence-based management of natural populations under strong human influence frequently requires not only estimates of survival but also knowledge about how much mortality is due to anthropogenic versus natural causes. This is the case particularly when individuals vary in their vulnerability to different causes of mortality due to traits, life-hi...

Background Marine threespine sticklebacks colonized and adapted to brackish and freshwater environments since the last Pleistocene glacial. Throughout the Holarctic, three lateral plate morphs are observed; the low, partial and completely plated morph. We test if the three plate morphs in the brackish water Lake Engervann, Norway, differ in body si...

Whole genome duplication (WGD) has been a major evolutionary driver of increased genomic complexity in vertebrates. One such event occurred in the salmonid family ∼80 million years ago (Ss4R) giving rise to a plethora of structural and regulatory duplicate-driven divergence, making salmonids an exemplary system to investigate the evolutionary conse...

The European eel (Anguilla anguilla) population has been in decline at least since the 1960s and reliable regional information, particularly on the spawner production and escapement (i.e. the silver eel life stage), is a requirement of the EU stock recovery regulation. Two comparable time series exist in Burrishoole (Ireland) and Imsa (Norway), wit...

Whole genome duplication (WGD) has been a major evolutionary driver of increased genomic complexity in vertebrates. One such event occurred in the salmonid family ~80 million years ago (Ss4R) giving rise to a plethora of structural and regulatory duplicate-driven divergence, making salmonids an exemplary system to investigate the evolutionary conse...

Ten years of experience with national salmon rivers – does this management scheme work? Atlantic salmon are found in >600 Norwegian rivers; in a newly introduced national scheme the salmon in 52 rivers and 29 ords have been given particularly strong protection. e scheme includes 75% of the salmon resource, including most of the large and productiv...

Interactions between birds and fish are often overlooked in aquatic ecosystems. We studied the influence of Atlantic salmon and brown trout on the breeding population size and reproductive output of the white‐throated dipper in a Norwegian river. Acidic precipitation led to the extinction of salmon, but salmon recolonized after liming was initiated...

Removing individuals from a wild population can affect the availability of prospective mates and the outcome of competitive interactions, with subsequent effects on mating patterns and sexual selection. Consequently, the rate of harvest-induced evolution is predicted to be strongly dependent on the strength and dynamics of sexual selection yet, the...

Body size can have profound impacts on survival, movement, and reproductive schedules shaping individual fitness, making growth a central process in ecological and evolutionary dynamics. Realized growth is the result of a complex interplay between life history schedules, individual variation, and environmental influences. Integrating all of these a...

Gene expression changes have been recognized as important drivers of adaptation to changing environmental conditions. Little is known about the relative roles of plastic and evolutionary responses in complex gene expression networks during the early stages of divergence. Large gene expression data sets coupled with in silico methods for identifying...

Sufficient genetic diversity can aid populations to persist in dynamic and fragmented environments. Understanding which mechanisms regulate genetic diversity of riverine fish can therefore advance current conservation strategies. The aim of this study was to investigate how habitat fragmentation interacted with population genetic diversity and indi...

Freshwater fishes live in complex environments, and are commonly structured into completely or partly reproductively isolated populations. This population structure is influenced by the local geography, the geological history of the landscape and present-day human-mediated changes in the aquatic landscape as well as long-distance translocations of...

The wide geographical distribution of brown trout Salmo trutta demonstrates a species with considerable plasticity as well as adaptability in various life history traits. Plasticity is the ability to respond phenotypically to abiotic and biotic factors. The Norwegian rivers running into salt water situated at 58–71 °N, 5–30 °E vary significantly in...