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Many salmonids, including brown trout (Salmo trutta), demonstrate alternative migration strategies under different environmental conditions, and as such, they are assumed to be predominantly facultative. Through experimental breeding for two generations, we produced purebred, crossed, and backcrossed groups of phenotypically resident, migratory, and hybrid strains of brown trout originating from a single watershed, and raised them in common- garden conditions. We examined the spring smolt migration tendency of the crosses in outdoor circular channels using passive integrated transponder telemetry at ages 2 and 3 years and found consistent and individually repeatable interstrain differences in migration distance and migration activity. The crossbred fish displayed intermediate behaviour, while later release to the migration channels with food augmentation affected the temporal dynamics of migration but not the total distances migrated. Migration tendency was positively associated with physiological smoltification and fish growth metrics. These results show that some earlier results interpreted as phenotypic plasticity may instead reflect genetic differences within and among populations. The intrinsic differences in reaction norms for both growth and migration tendency require novel management attention for effective conservation strategies. Key words: adfluvial, crossbreeding, food availability, growth rate, resident, 1 Introduction Animal migrations have evolved to maximize fitness in heterogeneous environments with spatiotemporal distributions of resources and risks of mortality (Taylor and Taylor 1977; Gross et al. 1988; Alerstam [...]

Chironomids are keystone primary benthic consumers with semi‐aquatic life cycles. They support aquatic and terrestrial consumers at higher trophic levels by conveying dietary nutrients, such as fatty acids. In this study, we combined field sampling and laboratory experiments to examine the effects of environmental parameters, including diet, on fatty acid composition and metabolism in chironomid larvae and imagines. Results from 53 lakes showed that lake size, depth, dissolved organic carbon (DOC) concentrations, and trophic state had only marginal effects on the content of long‐chain polyunsaturated fatty acids (LC‐PUFA) in chironomids. Compound‐specific stable hydrogen isotope analyses confirmed that chironomids actively bioconvert dietary fatty acid precursors to LC‐PUFA in all lake types, independent of nutrient or DOC concentrations. Moreover, fatty acid‐specific stable carbon isotope data indicated that the diet of chironomids was subsidized, particularly in oligotrophic lakes in spring, by terrestrial C18 fatty acid precursors that were converted to LC‐PUFA. Data from feeding experiments further confirmed that decreased dietary availability of LC‐PUFA enhanced the conversion of dietary short‐chain precursors to LC‐PUFA. These results suggest that chironomids are PUFA regulators that can sustain LC‐PUFA levels under varying environmental conditions. Furthermore, our results indicate that they bioconvert terrestrial low‐quality material to high‐quality resources, which, via chironomid emergence, support terrestrial food webs. Chironomids are abundant and widespread, and thus, the trophic transfer of LC‐PUFA can have significant implications for the fitness and production of upper trophic level consumers in both aquatic and terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Understanding the role of variation in host resistance and the multitude of transmission modes of parasites infecting hosts with complex behavioral interactions is essential for the control of emerging diseases. We used a discrete stage model to study the invasion dynamics of crayfish plague—an example of a detrimental disease—into a naïve host population that displays within‐population variation in resistance of environmental infections and juvenile classes that are safe from contacts with adults. In the model, infection sources include four age classes of crayfish, contaminated carcasses, and free‐dwelling zoospores. Disease transmission occurs via environment with a threshold infection density and through contacts, cannibalism, and scavenging of disease‐killed conspecifics. Even if the infection is fatal, coexistence of the host and the parasite can be facilitated by variance of resistance and survival of the hiding juveniles. The model can be applied in the control of emerging diseases especially in crayfish‐like organisms. [ABSTRACT FROM AUTHOR]

Wild, adfluvial brown trout (Salmo trutta) are iconic targets in recreational fisheries but also endangered in many native locations. We compared how fishing and natural selection affect the fitness-proxies of brown trout from two pure angling-selected strains and experimental crosses between an adfluvial, hatchery-bred strain and three wild, resident strains. We exposed age 1+ parr to predation risk under controlled conditions where their behaviour was monitored with PIT-telemetry, and stocked age 2+ fish in two natural lakes for experimental fishing. Predation mortality (16% of the fish) was negatively size-dependent, while capture probability, also reflecting survival, in the lakes (38.9% of the fish) was positively length- and condition-dependent. Angling-induced selection against low boldness and slow growth rates relative to gillnet fishing indicated gear-dependent potential for fisheries-induced evolution in behaviours and life-histories. Offspring of wild, resident fish showed slower growth rates than the crossbred strains. Strain effects suggested significant heritable scope for artificial selection on life-history traits and demonstrated that choices of fish supplementation by stocking may override the genetic effects induced by angling. Si les truites brunes (Salmo trutta) adfluviales sauvages constituent des cibles prisees dans les peches sportives, elles sont toutefois menacees en de nombreux endroits dans leur aire de repartition. Nous avons compare l'incidence de la selection naturelle et par la peche sur des variables substitutives de l'aptitude de truites brunes de deux lignees pures selectionnees par la peche sportive et de lignees experimentales issues des croisements d'une lignee adfluviale produite en ecloserie et de trois lignees residentes sauvages. Nous avons expose des tacons de plus d'un an a un risque de predation dans des conditions controlees dans lesquelles leur comportement a ete surveille par telemetrie a l'aide de radio-etiquettes passives integrees (PIT) et avons empoissonne deux lacs naturels avec des poissons de plus de deux ans pour la peche experimentale. La mortalite par predation (16 % des poissons) presentait une relation negative avec la taille, alors que la probabilite de capture dans les lacs (38,9 % des poissons), qui reflete egalement la survie, presentait des relations positives avec la longueur et l'embonpoint. La selection induite par la peche a la ligne d'individus plus hardis et de taux de croissance plus eleves par rapport a la peche au filet maillant indique un possible effet des engins de peche sur l'evolution induite par les peches des comportements et des cycles biologiques. La progeniture de poissons sauvages residents presentait des taux de croissance plus faibles que celle de lignees hybrides. Les effets sur les lignees indiqueraient qu'il existe un potentiel de transmission hereditaire significatif pour la selection artificielle de caracteres du cycle biologique et demontrent que les choix de supplementation de poissons par l'empoissonnement pourraient supplanter les effets genetiques induits par la peche sportive a la ligne. [Traduit par la Redaction], Introduction Recreational fisheries impose significant mortality on freshwater fish populations (Lewin et al. 2006). To compensate for fisheries harvest and incidental mortality or to offset natural recruitment bottlenecks, many populations [...]

Behaviour that is adaptive in captivity may be maladaptive in the wild and compromise postrelease survival of hatchery fish. The understanding of behavioural variation displayed immediately after release could help to improve hatchery protocols and development of behavioural tests for assessing the fitness of fish reared for releases. We characterized the postrelease behaviour of common-garden-raised offspring of wild resident, captive-bred migratory, and hybrid brown trout (Salmo traita) in two experiments: in small artificial channels and in high and low densities in seminatural streams. The results from seminatural streams showed that hatchery fish were more likely to disperse downstream from the initial stocking site compared with hybrid and wild strain fish. The small-scale experiment did not reveal this ecologically pivotal difference in postrelease performance among strains, and individual responses were inconsistent between the experiments. Circadian activity patterns did not differ among strains. These detailed observations of postrelease behaviour reveal important intrinsic differences in dispersal traits among brown trout strains and suggest that selective breeding and crossbreeding can substantially affect these traits. Un comportement bien adapte a la captivite pourrait s'averer mal adapte dans la nature et compromettre la survie de poissons d'ecloserie apres leur lacher. La comprehension des variations comportementales presentees immediatement apres le lacher pourrait aider a ameliorer les protocoles d'ecloseries et la mise au point de nouvelles epreuves pour evaluer l'aptitude des poissons eleves pour etre relaches. Nous avons caracterise le comportement apres le lacher de progeniture elevee en jardin commun de truites de mer (Salmo trotta) residentes sauvages, migratrices elevees en captivite et hybrides dans deux experiences, a savoir : dans de petits chenaux artificiels et dans des cours d'eau semi-naturels, a forte et faible densites. Les resultats pour les cours d'eau semi-naturels montrent que les poissons d'ecloserie etaient plus susceptibles de se disperser en aval a partir du site d'empoissonnement initial que les poissons hybrides et de lignee sauvage. L'experience a petite echelle n'a pas fait ressortir cette difference cle sur le plan ecologique de la performance apres le lacher entre les lignees, et les reactions individuelles n'etaient pas coherentes d'une experience a l'autre. Les motifs d'activite circadienne des differentes lignees ne presentaient pas de difference. Ces observations detaillees du comportement apres le lacher revelent des differences intrinseques importants des caracteres associes a la dispersion entre differentes lignees de truites brunes et indiqueraient que la reproduction selective et le croisement peuvent avoir une incidence considerablement sur ces caracteres., Introduction Enormous numbers of captive-bred, hatchery-raised fish are released worldwide to support fisheries, enhance weakened natural populations, or introduce new fish populations (Cowx 1994). Yet the stockings too often fail [...]

Brown trout (Salmo trutta) exhibit highly diverse life histories varying from resident, slow-growing, and early maturing to migratory, fast-growing, and late maturing, even within single watersheds. We sampled 11 locations within the transboundary Finnish-Russian River Koutajoki watershed to evaluate genomic differences among mainstem and headwater sites, of which some are isolated by migration barriers. Restriction site associated sequencing (RADSeq) revealed that the most headwater localities supported unique, isolated populations with generally lower heterozygosity compared with the mainstem populations. The sampled migratory adults in the three main stems showed signals of admixture despite small but statistically significant genetic divergence, while the headwater populations, except for two, showed a high level of divergence and a lack of admixture. These results suggest that most of the headwater populations consist of resident brown trout and that the population genetic structuring is often maintained even in the absence of migration barriers. Our results have clear implications for fisheries management and conservation; each brown trout subpopulation represents an evolutionarily important unit with unique genetic makeup and life history variation. Les truites fario (Salmo trutta) presentent differents types de strategies de vie, variant entre des formes residentes a croissance lente et maturite retardee et des formes migrantes a croissance rapide et maturite precoce, qui peuvent coexister dans un meme bassin versant. Nous avons echantillonne 11 rivieres dans le bassin versant finno-russe de la riviere Koutajoki afin d'etudier les differences genomiques entre les populations presentes dans les cours d'eau principaux du systeme et les populations dans leurs affluents, parfois isolees par des obstacles a la migration. Le sequencage d'etiquettes associees a des sites de restrictions revele que la plupart des affluents contiennent des populations uniques et isolees presentant une heterozygotie generalement plus faible que celle des populations des cours d'eau principaux. Les adultes migrants echantillonnes dans les trois cours d'eau principaux presentent un melange genetique entre eux malgre une divergence genetique faible, bien que statistiquement significative, alors que les populations des affluents, a deux exceptions pres, presentent une grande divergence et une absence de melange genetique. Ces resultats donnent a penser que les affluents renferment majoritairement des populations residentes et que les structures genetiques sont souvent maintenues meme en l'absence d'obstacles a la migration. Notre etude est importante pour la conservation et la gestion des ressources halieutiques, soulignant le fait que chaque sous-population de truites fario represente une unite genetique independante avec ses propres strategies de vie. [Traduit par la Redaction], Introduction Salmonids from genera Salmo, Oncorhynchus, and Salvelinus are among the most famous and economically important migratory fishes (Quinn 2005; Harris and Milner 2007). Many species in genus Salmo perform [...]

Browning of surface waters, also known as brownification, is a process of decreasing water transparency, particularly in boreal lakes surrounded by intensively managed forests and wetlands. In this paper, we review the ecological consequences and ecosystem‐based management (EBM) of browning through a systematic review approach and adopt an interdisciplinary approach to formulating new governance of this complex phenomenon. To understand the effects of browning on the recreational value of freshwaters, we present primary survey data on public perceptions of recreational fishing tourists on water quality in Finland. We identify a need to develop EBM beyond the EU's Water Framework Directive (WFD) to fully account for the extensive implications of browning. We also highlight the need for a better understanding of the within‐lake microbial processes to estimate the browning‐associated changes in the greenhouse gas balance of lakes. Tourist perceptions of the quality of waterbodies in Finland were largely in agreement with the general proportion of waterbodies classified in a good or excellent ecological status class, but these perceptions may be detached from biological quality assessment criteria. Consequently, we suggest that the EBM of inland waters should improve the utilization of information on not only biogeochemical processes but also users' perspectives on aquatic ecosystems beyond the EU WFD. [ABSTRACT FROM AUTHOR]

Animals, including fish, display individually consistent behavioral differences that may affect an individual's vulnerability not only to predation, but also to fishing. Compared with complex natural environments, plain hatchery environments might induce development of behaviors that increase vulnerability to fishing, which would in turn have major implications for the management of stocks by supportive releases. We studied whether the vulnerability of hatchery-reared brown trout (Salmo trutta) to angling could be predicted by rearing method (standard versus enriched) or behavioral variation that was assessed using long-term observations of moving activity in groups. High moving activity in the beginning of the behavioral tests (i.e., exploration behavior) predicted increased vulnerability to angling independently of fish body size. Standard rearing promoted high exploration rate among fish, whereas enriched rearing promoted improvement in body condition in (semi-)natural conditions. However, the driving influence of hunger on vulnerability could not be ruled out, as the most explorative standard-reared fish appeared unable to maintain their body condition during the experiments. This study provides direct evidence that standard hatchery rearing method promotes behaviors that directly predict vulnerability to angling. Les animaux, y compris les poissons, presentent des differences de comportement individuelles coherentes qui peuvent avoir une incidence sur la vulnerabilite de l'individu non seulement a la predation, mais egalement a la peche. Comparativement aux milieux naturels plus complexes, les milieux d'aleviniere pourraient induire l'apparition de comportements qui accroissent la vulnerabilite a la peche, ce qui, du coup, aurait d'importantes consequences pour la gestion des stocks par lachers de soutien. Nous avons tente de determiner si le type de methode d'elevage (normale ou enrichie) ou les variations comportementales etablies a partir d'observations de longue duree sur l'activite de deplacement au sein de groupes permettaient de predire la vulnerabilite a la peche sportive des truites de mer (Salmo trutta) elevees en aleviniere. Une forte activite de deplacement au debut des essais comportementaux (c.-a-d., un comportement d'exploration) predisait une vulnerabilite accrue a la peche sportive, independamment de la taille du corps des poissons. L'elevage normal favorisait un taux d'exploration eleve chez les poissons, alors que l'elevage enrichi favorisait l'amelioration de l'embonpoint dans des conditions (semi-)naturelles. L'influence de la faim sur la vulnerabilite ne peut toutefois etre exclue, puisque les poissons issus de l'elevage normal presentant le comportement d'exploration le plus fort semblaient incapables de maintenir leur embonpoint durant les experiences. L'etude fournit des preuves directes du fait que la methode normale d'elevage en aleviniere favorise des comportements qui expliquent directement la vulnerabilite a la peche sportive. [Traduit par la Redaction], Introduction Research on ecological and evolutionary responses of wild animal populations to anthropogenic selection has been intensive during the last decade (Allendorf and Hard 2009; Darimont et al. 2009). Although [...]

Management of inland recreational fisheries would benefit from stock abundance and size structure data. Feasibly standardised angling methods such as ice fishing could produce representative catch‐per‐unit‐effort (CPUE) information on the abundance of different‐sized fish in small lakes. Here, we first used standard Nordic multimesh gillnets to obtain number‐per‐unit‐effort (NPUE), biomass‐per‐unit‐effort (BPUE) and size structure data on Eurasian perch (Perca fluviatilis) stocks in 11 small boreal lakes in summer. Second, the same lakes were ice‐fished by voluntary anglers using a pre‐defined, loosely standardised protocol to obtain angling‐based NPUE, BPUE, and length frequency distributions. Effects of environmental variables such as water oxygen concentration and light penetration on angling catch rates were controlled statistically. Neither perch Nordic gillnet NPUE nor BPUE corresponded to ice‐fishing CPUEs. However, the length distribution of the catch did not differ between methods. Our results imply that traditional ice fishing applying natural baits is relatively unselective for fish size and could produce valid length‐based indicators for management purposes while angling CPUE was poorly related to Nordic gillnet CPUE. [ABSTRACT FROM AUTHOR]