The global mean temperature is predicted to increase by up to 5 °C during this century. For fish, being ectotherms, temperature is one of the most important environmental factors, influencing them in a number of different ways, including effects on physiological traits, timing of life history events and behavior. Atlantic salmon has been shown to grow faster after being incubated at warmer temperatures. One possible explanation for this could be that the increased incubation temperature causes decreased metabolic rates. The aim of this project was to examine whether this is true. Atlantic salmon eggs were incubated in three different temperature regimes: natural temperature conditions, heated water and a mixed temperature treatment, where eggs were incubated in increased temperature until the beginning of January and after that subjected to natural temperature conditions. Ventilation rate, a proxy for metabolism, was measured for fish from each treatment group, as well as fish length and weight. The results revealed significantly lower ventilation rates of the fish from the heated temperature treatment, but not of the fish from the mixed temperature treatment. This suggests that an increased incubation temperature causes lowered rates of metabolism in Atlantic salmon, and that the change occurs later than early January. Because of differences in size and life stage between fish from the different groups however, the results are uncertain and call for further investigations. A lowered metabolic rate will affect the fish’s behavior. A further development might therefore be to study fish survival in the wild in relation to a fish’s metabolic rate. / Jordens medeltemperatur beräknas öka med upp till 5 °C det här århundradet. För fiskar, som är ektotermer, är temperatur en av de viktigaste abiotiska faktorerna och påverkar dem på en mängd olika sätt, bland annat genom förändring av fysiologiska attribut, tidpunkter för steg i livscykeln och beteende. Lax har visats växa snabbare efter att ha blivit inkuberade i varmare vattentemperatur. En möjlig förklaring till det kan vara att en förhöjd inkuberingstemperatur orsakar en lägre metabolism. Det här projektet syftade till att undersöka om så är fallet. Ägg från lax inkuberades i tre olika temperaturförhållanden: naturliga temperaturförhållanden, förhöjd temperatur och en blandad temperaturbehandling, där ägg inkuberades i förhöjd temperatur till början av januari, varefter de utsattes för naturliga temperaturförhållanden. Gälslagsfrekvens, som fungerar som en indikator för metabolism, mättes på fisk från varje behandlingsgrupp, samt fiskarnas längd och vikt. Resultaten visade signifikant lägre gälslagsfrekvenser hos fiskarna från behandlingen med förhöjd temperatur, men inte hos fiskarna från behandlingen med blandad temperatur. Detta indikerar att en förhöjd inkuberingstemperatur orsakar en lägre metabolism hos lax, och att förändringen sker senare än tidiga januari. På grund av skillnader i storlek och livsstadier hos fiskarna från de olika grupperna är resultaten dock osäkra, vilket gör att ytterligare studier behövs. En lägre ämnesomsättning påverkar fiskars beteende. En uppföljning kan därför vara att studera fiskars överlevnad i det vilda i relation till deras metabolism.

Efficient control of sea lice is a major challenge for the sustainable production of farmed Atlantic salmon (Salmo salar (Linnaeus, 1758)). These marine ectoparasites feed on mucus, skin and blood of their hosts, thereby reducing the salmon’s growth rate and overall health. In the northern hemisphere, the most prevalent species is Lepeophtheirus salmonis (Krøyer, 1837). In 2006, global costs of sea lice infections are estimated to have exceeded €300 million, with the majority spent on a limited number of chemical delousing agents. Emamectin benzoate (EMB; SLICE®), an avermectin, has been widely used since its introduction in 2000, due to its convenient administration as an in-feed medication and its high efficacy against all parasitic stages of L. salmonis. However, over-reliance on a single or limited range of medicines favours the emergence of drug resistance and, as a result, the efficacy of this compound in treating L. salmonis has decreased in recent years, as reported from e.g. Chile, Norway, Scotland and Canada. Declining efficacy underlines the need for an improved understanding of the molecular mechanisms underlying EMB drug resistance in L. salmonis. Elucidation of these mechanisms would allow for improved monitoring tools, earlier detection of developing resistance, extended usability of current delousing agents and development of new parasiticides. The work described in this thesis sets out to examine the molecular mechanisms underlying EMB resistance in L. salmonis. In earlier studies, research in nematodes and arthropods has linked drug efflux transporters belonging to the family of ATP-binding cassette (ABC) transporters to ivermectin (IVM) resistance, a parasiticide with high chemical similarity to EMB. ABC transporters such as permeability glycoprotein (P-gp), transport a wide range of substrates, including drugs, and have been suggested to provide a potential molecular mechanism through which EMB resistance might be mediated in sea lice. As an example of such mechanisms, increased expression of P-gp is one of the causative factors for drug resistance in human cancer cells and avermectin resistance in nematode parasites such as Caenorhabditis elegans or Haemonchus contortus. Initial research involved screening for novel salmon lice P-gps that might contribute to EMB resistance. A novel P-gp, SL-PGY1, was discovered using a combined bioinformatic and molecular biological approach. The expression was compared in two well-characterised L. salmonis strains differing in their susceptibility to EMB (S = susceptible, R = resistant). Prior to EMB exposure, mRNA levels did not differ from each other, while, after 24 h exposure, a 2.9-fold increase in SL-PGY1 mRNA expression was observed in the R strain. SL-PGY1 appears not to be a major factor contributing to reduced EMB susceptibility, although it could play a role, as expression levels increased upon exposure to EMB. A further four additional drug transporters (ABC C subfamily) were also discovered showing high homology to multidrug-resistance proteins (MRP). The relative expression levels of each MRP was compared in the strains S and R, before and after exposure to EMB. No significant changes were found in their expression patterns. If ABC drug transporters mediate the efflux of EMB and thereby reduce the intracellular concentrations of the drug in exposed animals, the inhibition of those ABC drug transporters was expected to lead to higher intracellular levels of EMB. This could result in an enhanced toxic effect when EMB is co-administered with an inhibitor. Two known inhibitors of human P-gps and MRPs, cyclosporin A (CSA) and verapamil (VER), were co-administered with EMB. CSA increased the toxic effect of EMB in both tested strains, implying that the targets of CSA are expressed at comparable levels and that they may be part of the mechanism conferring EMB resistance. VER increased the toxic effect of EMB in the R strain, but had no significant effects on the S strain. This implies that the expression of factors inhibited by VER differs between the two L. salmonis strains. It is hypothesised that a number of ABC transporters with distinct, yet overlapping patterns of inhibitor specificity are affected by those inhibitors. The search for drug-resistance conferring genes was complemented with a systematic, genome-wide survey of ABC transporters in L. salmonis to find additional members of this important gene family. Next-generation high-throughput RNA sequencing (RNA-seq) was employed to assemble a reference transcriptome from pooled total RNA of salmon lice at different development stages. The transcriptome was assembled against the L. salmonis genome and annotated. Thirty-nine putative ABC transporters were found. Of further interest were transcripts of the subfamily B, C and G, as they contain drug-transporting ABC proteins. For the ABC B subfamily, one full (SL-PGY1) and three half transporter transcripts were found. Only full transporters are known to transport drugs and SL-PGY1 is apparently not a major factor contributing to EMB resistance. Fourteen ABCC sequences were found – 11 MRPs and 3 homologues to sulfonylurea receptors. Of interest are MRPs, as they contribute to drug detoxification in humans and invertebrates. Four MRPs had been identified previously and their expression ratios did not differ between S and R strain parasites. Seven sequences belonging to ABCG subfamily were found. However, none of the L. salmonis ABCG transcripts identified showed sufficient homology to known drug transporters in other species. With the currently limited understanding of the mechanisms conferring EMB resistance, monitoring the susceptibility of L. salmonis subpopulations is essential. Dose-response bioassays are currently widely used. Tests with pre-adult II or adult parasites requires relatively large numbers of parasites (~150) to conduct this type of bioassay, which may not always be available. Addressing this issue, we tested the feasibility of a single-dose bioassay (requiring fewer test animals than dose-response bioassays) to discriminate between L. salmonis strains with differing EMB susceptibility. This alternative approach uses time-course toxicity analysis, where the toxic effect of EMB is monitored over time. After clearly defining the effect criteria, we found that it is possible to discriminate between those L. salmonis strains. However, while requiring fewer test animals, time course toxicity analysis is more labour-intensive, but the alternative design can be suitable under certain circumstances. The work reported here has provided new knowledge concerning the mechanisms of EMB resistance in sea lice. Several novel putative drug transporters have been identified, an important first step toward unravelling the complex interactions of genes involved in EMB resistance in this commercially important parasite.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Les poissons vivant au sein d’une rivière sont soumis à des variations circadiennes de température pouvant influencer la croissance, la digestion et le métabolisme standard. Les modèles bioénergétiques utilisant les fonctions métaboliques pour déterminer la croissance d’un poisson ont souvent été élaborés avec des poissons acclimatés à des températures constantes. Ces modèles pourraient sous-estimer l’énergie dépensée par un poisson soumis à des températures fluctuantes. En utilisant la respirométrie par débit intermittent, les objectifs de ce travail étaient : (1) de quantifier les différences entre les taux métaboliques standards de poissons acclimatés à une température constante (20.2 oC ± 0.5 oC) et à des fluctuations circadiennes de température (19.8 oC ± 2.0 oC; 19.5 oC ± 3.0 oC) et (2) comparer deux méthodologies pour calculer les taux métaboliques standards de poissons sujets aux fluctuations circadiennes de températures : respirométrie (a) en température constante ou (b) en température fluctuante. Les poissons acclimatés à des fluctuations circadiennes de température ont des taux métaboliques standards plus élevés que des poissons acclimatés à une température constante. À 20.2 oC ± 0.5 oC, les taux métabolique standards ont été de 25% à 32% plus bas pour des poissons maintenus à une température constante que pour des poissons gardés sous des fluctuations circadiennes de température. Les méthodologies utilisées pour estimer les taux métaboliques standards de poissons sujets aux fluctuations de température offrent des résultats similaires. / Fish that inhabits river are subjected to circadian fluctuations in water temperature. These fluctuations can influence growth, digestion and metabolic processes. Bioenergetic models are traditionally modeled using data recorded from fish kept at constant water temperatures. These models could underestimate the energy spent by fish subjected to fluctuating temperatures. Thus, with intermittent-flow respirometry, the objectives of this study were to: (1) quantify the differences between standard metabolic rates of fish acclimatized to a constant temperature (20.2 oC ± 0.5 oC) and two circadian fluctuating temperatures (19.8 oC ± 2.0 oC; 19.5 oC ± 3.0 oC) and (2) compare two methodology for calculate standard metabolic rates of fish subjected to circadian fluctuating temperatures: intermittent-flow respirometry with (a) constant temperature or (b) fluctuating temperatures. Fish held at circadian fluctuating temperatures have higher standard metabolic rates than fish acclimatized to a constant temperature. At 20.2 oC ± 0.5 oC, standard metabolic rates was 25% to 32% lower for fish held at constant temperature than for fish held under circadian fluctuations. However, results of the two different strategies used to calculate standard metabolic rates of fish subjected to circadian fluctuating temperatures did not differ.

Le saumon Atlantique fait partie du patrimoine écologique et économique du bassin de l’Adour. Dans le cadre de la gestion actuelle du saumon dans ce bassin, l’origine natale des géniteurs, le taux de retour des individus d’origine piscicole, le taux de homing sur chaque sous-bassin ou encore le soutient par des géniteurs extérieurs au bassin de l’Adour sont des thématiques qui restent sans réponses. Ce projet propose donc de tester le potentiel de la géochimie des otolithes sur le saumon Atlantique du bassin de l’Adour. Nos travaux démontrent que la variation géographique de la composition chimique de l’eau dans 12 rivières colonisées par le saumon, associée à un enregistrement dans l’otolithe proportionnel à la signature géochimique du milieu de vie, permettent de discriminer l’origine géographique des individus. La combinaison des signatures élémentaires (Sr:Ca et Ba:Ca) et surtout l’isotopie du Sr (temporellement plus stable et sans fractionnement biologique) dans les otolithes améliore la précision du classement à l’échelle de la rivière de développement. En se basant sur la transmission de signatures géochimiques (élémentaires et isotopiques) transgénérationelles entre la femelle reproductrice et les otolithes des embryons produits par cette dernière, nous avons discriminé avec succès les individus nés en rivière de ceux nés en pisciculture. Le classement des géniteurs (180 individus) selon leur rivière natale a confirmé que le sous bassin du gave d’Oloron, et plus particulièrement le gave d’Ossau, reste le lieu qui produit le plus de saumon de retour. De façon non négligeable, le gave de Pau contribue lui aussi au renouvellement de la population (10 d’origine piscicole et 6 d’origine naturelle). 18 saumons sur 180 sont issus de l’alevinage (soit 10%); la majorité s’étant développée dans le sous-bassin du gave de Pau. Par ailleurs, nous avons mis à jour l’existence de périodes au cours de la vie des juvéniles (changements de milieu: sac vitellin—milieu extérieur et pisciculture—rivière) durant lesquelles l’enregistrement du Ba dans l’otolithe n’est pas en relation avec la chimie de l’eau. L’originalité de notre approche est d’avoir étudié l’influence des facteurs endogènes et environnementaux chez des poissons ayant vécu dans le milieu naturel ou ayant séjourné en milieu naturel contrôlé. Nos travaux mettent l’accent sur la complexité de l’intégration du rapport Ba:Ca dans l’otolithe et démontrent l’utilité des éléments traces et des isotopes du Sr comme « tag naturel » pour distinguer l’origine natale du saumon Atlantique. / The Adour basin holds one of the largest populations of Atlantic salmon in southern Europe exploited by commercial and sport fisheries. Determining the relative contributions of individual rivers and hatcheries to the Adour basin populations becomes crucial to understand key sources that contribute the most to its persistence. We successfully used Sr:Ca, Ba:Ca and 87Sr:86Sr ratios as natural tags for determining the natal origins of adults from 12 tributaries. Success in discriminating between fish from different sites was greatest using Sr isotopes since the latter remained relatively constant across years at a given location. Geochemical signatures from core regions of the otolith were also used to identify fish from hatchery or naturally spawned sources. The predominance of adults spawned in the Ossau River among returning adults corresponded with long-term juvenile production trends in the Ossau River. Despite the limited upstream accessibility of the Pau River, our study demonstrated that Atlantic salmon recruits can successfully leave this river to join the adult population in the Adour basin. We observed relatively clear separation between hatchery and wild juveniles using both Sr:Cacore (wild > 2.5 and hatchery < 0.80) and 87Sr:86Srcore (wild < 0.710 and hatchery > 0.710). The return of hatchery reared fish as adult spawners represented 10% of the total sampled fish we analyzed. Almost all adults, previously identified as belonging to the Ouzom River, were hatchery produced. Adults originated from the Pau River were either wild or hatchery reared fish. We also conducted field controlled experiments that characterized the elemental uptake process in juvenile Atlantic salmon otoliths during freshwater residency. Physiological effects influenced Ba deposition. Ba:Ca otolith profiles from hatchery-reared and field collected fish were characterised by a peak at yolk absorption mark. Hatchery-reared fish stocked in a river also displayed a peak of Ba:Ca following transfer which was not related to the water chemistry. Our experiment revealed a 20-day lag time between initial Ba:Cawater changes and Ba:Caotolith saturation. Results suggested that such effects should be considered during any attempts to determine rivers of origin of Atlantic salmon based on otolith elemental composition or reconstruct the movement of individual fish among and within streams.

La fragmentation des habitats ainsi que la réduction de leur disponibilité sont des menaces importantes pour les écosystèmes, notamment aquatiques. La disponibilité et la qualité des sites de fraie du saumon Atlantique peut donc être limitante dans certaines rivières. Après la migration en rivière, les femelles saumon vont chercher à s'établir dans un des sites de fraie disponibles. La distribution spatiale des femelles va alors influer sur la distribution spatiale des mâles reproducteurs qui vont chercher soit à monopoliser plusieurs femelles (pour les mâles dominants), soit à les approcher en adoptant un comportement "furtif" (pour les mâles satellites). L'accès des mâles aux femelles va donc dépendre de la distribution spatiale des femelles et des déplacements des mâles dans la rivière. La distribution des femelles va également jouer sur la distribution spatiale des juvéniles, les concentrant à certains endroits. Cette concentration peut augmenter la mortalité densité-dépendante qui modifie la dynamique de la population. Cette thèse avait pour but d'évaluer comment l'utilisation de l'espace des potentiels reproducteurs, c'est à dire les individus matures, influence la dynamique de la population et la sélection sexuelle.Des séries temporelles de stock (oeufs déposés) et de recrutement (juvéniles) pour la population de saumon de la Nivelle ont été associées à des mesures de l'agrégation spatiale des nids creusés par les femelles. L'effet des déplacements et de la distribution des reproducteurs sur leur participation à la reproduction a notamment été testé via la reconstruction du réseau d'interactions sexuelles dans la Nivelle.J'ai ainsi démontré que l'agrégation spatiale des nids influa sur la variabilité du recrutement mais pas sur le recrutement moyen. Cette agrégation qui résulte de l'agrégation des femelles a également été liée au nombre de reproducteurs ayant engendrés des juvéniles. Le réseau d'interactions sexuelles a permis de mettre en évidence une structure sociale locale au sein de la population. Cette structure et les compétiteurs présents pouvaient par exemple diminuer le succès reproducteur des mâles. Notamment, les tacons matures qui participent à la reproduction avant de migrer en mer renforçaient la compétition sexuelle dont les mâles dominants faisaient l'objet. Enfin, ces mêmes tacons matures adoptèrent des comportements spatiaux du fait de leur statut de maturité avec des individus bougeant peu et des individus se déplaçant vers l'amont. Ces comportements spatiaux influaient leur participation à la reproduction, l'étendue des domaines de vie et les déplacements vers l'amont augmentaient la probabilité de rencontrer une femelle.Mes résultats m'ont permis de mettre en évidence l'effet de l'utilisation de l'espace des potentiels reproducteurs sur la dynamique de la population et sur la sélection sexuelle. Ainsi, en combinant différentes échelles spatiales et temporelles il a été montré que l'agrégation des femelles pouvait être bénéfique pour la dynamique de la population. Il semble que les femelles tendent à s'agréger d'abord sur les meilleurs sites de fraie avec une plus forte stabilité environnementale. Cette distribution des femelles affecta la capacité des mâles à monopoliser plusieurs femelles, une agrégation modérée permettant une monopolisation. La participation des mâles furtifs anadromes ou tacons matures était également dépendante de l'agrégation des femelles. Il apparait que la disponibilité d'habitats adéquats pour la reproduction semble limitante dans la Nivelle et notamment du fait de la présence de barrages. Ce manque semble affecter le système d'appariement de la population et la sélection sexuelle y opérant. Des mesures visant à améliorer la qualité des sites de fraie déjà disponibles ainsi que leur accessibilité pourraient être envisagées. / Habitat fragmentation and reduction in the availability of suitable habitats are significant threats to ecosystems in particularly for freshwater ones. For instance, accessibility, availability, and quality of breeding sites of Atlantic salmon, \textit{Salmo salar}, can be restricting in some rivers due to human activities and dams. Such threats may affect distribution of potential breeders because after their up-river migration, salmon females distribute within available breeding sites. Spatial distribution of females determines the spatial distribution of breeder males. Dominant males try to monopolise several females, whereas subordinate males adopt a sneaky behaviour. Access to females by males depends on the spatial distribution of females and on males' displacements within a river. The spatial distribution of females generates the spatial distribution of juveniles, aggregating them at some breeding sites. The latter aggregation of juveniles may raise the density-dependent mortality with potential consequences on population dynamics. The thesis aims to assess how space use of potential breeders, namely mature individuals able to spawn or fertilise eggs, influence population dynamics and sexual selection.I combined different approaches and different temporal and spatial scales to potential effects of space use of potential breeders. Time series of stock (deposited eggs) and of recruitment (juveniles) for the salmon population of the Nivelle River were combined with measures of spatial aggregation of nests. The effects of displacements and spatial distribution of potential breeders on their participation in reproduction were tested through inferring the sexual network of the population.I found that spatial aggregation of nests improved the recruitment variability but did not affect the average recruitment. The spatial aggregation of nests resulting from female aggregation was also linked to the number of effective breeders through a U-shaped curve. Such relationships suggested mate monopolization dependent on the spatial aggregation of females. The negative effect of the spatial isolation of females on their number of mates also suggest such mate monopolization. Then, the inferred sexual network enabled me to highlight a local social structure within the population. The latter structure and social competitors impacted the reproductive success of anadromous males. The participation of mature parr was one of the factors diminishing the sexual competition faced by anadromous males. Finally, mature parr were more mobile and moved more upstream than immature parr. Spatial behaviours of mature parr were linked to their participation in reproduction, individuals exhibiting wider home ranges had a higher probability to encounter females.Altogether my results show that space use of potential breeders affect both population dynamics and sexual selection. Then, spatial aggregation of females and of their nests can be beneficial for population dynamics as shown by combining different temporal and spatial scales. Females seemed to aggregate within the best breeding sites with a better environmental stability. The spatial distribution of females affected the ability of males to monopolise several females and participation of sneaky males. The availability of suitable good breeding habitats seemed restricting in the Nivelle, potentially due to the presence of impassable upstream dams. The lack of suitable breeding sites seemed impacting the mating system of the population and the sexual selection operating in. Some management actions to improve the quality of breeding sites and their availability could be planned.

Les poissons vivant au sein d’une rivière sont soumis à des variations circadiennes de température pouvant influencer la croissance, la digestion et le métabolisme standard. Les modèles bioénergétiques utilisant les fonctions métaboliques pour déterminer la croissance d’un poisson ont souvent été élaborés avec des poissons acclimatés à des températures constantes. Ces modèles pourraient sous-estimer l’énergie dépensée par un poisson soumis à des températures fluctuantes. En utilisant la respirométrie par débit intermittent, les objectifs de ce travail étaient : (1) de quantifier les différences entre les taux métaboliques standards de poissons acclimatés à une température constante (20.2 oC ± 0.5 oC) et à des fluctuations circadiennes de température (19.8 oC ± 2.0 oC; 19.5 oC ± 3.0 oC) et (2) comparer deux méthodologies pour calculer les taux métaboliques standards de poissons sujets aux fluctuations circadiennes de températures : respirométrie (a) en température constante ou (b) en température fluctuante. Les poissons acclimatés à des fluctuations circadiennes de température ont des taux métaboliques standards plus élevés que des poissons acclimatés à une température constante. À 20.2 oC ± 0.5 oC, les taux métabolique standards ont été de 25% à 32% plus bas pour des poissons maintenus à une température constante que pour des poissons gardés sous des fluctuations circadiennes de température. Les méthodologies utilisées pour estimer les taux métaboliques standards de poissons sujets aux fluctuations de température offrent des résultats similaires. / Fish that inhabits river are subjected to circadian fluctuations in water temperature. These fluctuations can influence growth, digestion and metabolic processes. Bioenergetic models are traditionally modeled using data recorded from fish kept at constant water temperatures. These models could underestimate the energy spent by fish subjected to fluctuating temperatures. Thus, with intermittent-flow respirometry, the objectives of this study were to: (1) quantify the differences between standard metabolic rates of fish acclimatized to a constant temperature (20.2 oC ± 0.5 oC) and two circadian fluctuating temperatures (19.8 oC ± 2.0 oC; 19.5 oC ± 3.0 oC) and (2) compare two methodology for calculate standard metabolic rates of fish subjected to circadian fluctuating temperatures: intermittent-flow respirometry with (a) constant temperature or (b) fluctuating temperatures. Fish held at circadian fluctuating temperatures have higher standard metabolic rates than fish acclimatized to a constant temperature. At 20.2 oC ± 0.5 oC, standard metabolic rates was 25% to 32% lower for fish held at constant temperature than for fish held under circadian fluctuations. However, results of the two different strategies used to calculate standard metabolic rates of fish subjected to circadian fluctuating temperatures did not differ.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

There are five endemic populations of migratory Atlantic salmon (Salmo salar, Salmonidae) and brown trout (Salmo trutta, Salmonidae) remaining in Lake Vänern, whereof two are salmon and three are trout. There is one population of each species in Klarälven, also one of each in Gullspångsälven and there is a population of trout still remaining in Tidan River. Since the beginning of the 20th century endemic populations of salmon and trout have either vanished or declined dramatically due to the construction of hydropower in the rivers around the lake, and still today the future of the remaining populations remains uncertain. To manage salmonid fishes effectively more knowledge of their ecology throughout their different life-stages is needed. A large part of the Lake Vänern salmonoids lives are spent in the lake, where a mayor mortality factor is recreational fishing, especially angling. Estimation of fishing effort and catch is important in order to remain a sustainable fishery. In Lake Vänern commercial fishers are bound to report their catch, but anglers are not, -even though they are now thought to be responsible for the largest proportion of the catch. Angler interviews and access point surveys are the best ways to get accurate information in order to assess sport fish effort and catch. There are drawbacks of this method though that includes large costs, logistical problems and biased results due to the higher chance of interviewing the most avid anglers. To hand out mail-surveys is a kind of off-site survey that is less costly compare to interviews, but the drawbacks are bigger in getting correct information due to biased results from non-respondence. A study was conducted to compare an interview-survey with a mail-in survey, in which the interviews were conducted in Lillängshamnen, a port on the northern coast of Lake Vänern, and the mail-in surveys were distributed in different ports around the lake, though not in Lillängshamnen. This study shows a significant difference in catch per boat day between the interviews and mail-in survey. To find out more about how to develop the interview-survey there was also an analysis done on the correlation between weather and the number of interviews that were collected. One could find a negative correlation between numbers of interviews collected and the wind ratio, where very few interviews were collected once the wind speed measured more than 5-8 meters per second. There are improvements to be made both for the conduction of interviews and mail-in surveys, including more staff for conducting interviews at different ports and follow-ups on the non-respondents for the mail-in survey. / Av atlantlax (Salmo salar, Salmonidae) och öring (Salmo trutta, Salmonidae) finns idag fem endemiska populationer kvar i Vänern varav två är av lax och tre av öring. Det finns en klarälvsvariant av båda arterna, likaså finns det en gullspångsvariant av varje och sen finns även en öringpopulation kvar i Tidan. Sen början av 1900-talet har populationer av lax och öring utrotats eller minskat kraftigt till följd av vattenkraftens utbyggnad i vattendragen runt Vänern, och än idag är de resterande populationernas framtid oviss. För att kunna förvalta laxfiskarna på ett bra sätt krävs kunskaper om deras ekologi i dess olika livsstadier. En stor del av laxfiskarna runt Vänerns liv tillbringas i Vänern, där en mortalitetsfaktor består av fritidsfisket, då främst trolling. Uppskattning av ansträngning och fångst är viktigt för att hålla fisket i sjön på en hållbar nivå. Yrkesfisket måste rapportera all sin fångst men detta krävs inte av trollingfisket som idag tros stå för den största proportionen lax- och öringsfångst i Vänern. Genomförandet av intervjuer är en typ av plats- och åtkomstpunktsundersökning och är den bästa metoden att samla in korrekt information för att uppskatta sportfiskets ansträngning och fångst. Det finns dock nackdelar i form av stora kostnader, svår logistik och vinklade resultat då de mest entusiastiska fiskarna löper större chans att bli intervjuade. Att dela ut enkäter är en form av distansundersökning och även brevundersökning som kostar betydligt mindre än att genomföra intervjuer men brister vad gäller svarsfrekvens som i sin tur leder till vinklade resultat. En studie gjordes för att jämföra intervjuer med enkäter, där intervjuer genomfördes i Lillängshamnen på Vänerns norra kust och enkäter delades ut i olika hamnar runt hela Vänern, dock ej i Lillängshamnen. Denna undersökning visade att enkäter har en signifikant större fångst per båt än intervjuer. För att ta reda på mer om hur genomförandet av intervjuer skulle kunna förbättras undersöktes hur vädret påverkade antalet intervjuer som genomfördes. Man fick en negativ korrelation mellan antalet genomförda intervjuer och vindhastighet där ytterst få intervjuer genomfördes i vindhastigheter över 5-8 meter per sekund. Det finns förbättringspotential vad gäller både genomförandet av intervjuer och enkätundersökningar, bland annat mer personal till att kunna intervjua fler folk i olika hamnar och uppföljning på de enkäter som inte svarats på.

Fiskars passager genom vattenkraftverk är förenat med hög dödlighet. För att minska vattenkraftens påverkan på fiskbestånd har olika fiskledare utvecklats. I denna laboratoriestudie utvärderades tre typer av icke-fysiska fiskledare och deras effektivitet i att leda odlade smolt av Atlantlax (Salmo salar L.) till en önskad passage. Målet med denna studie var att undersöka om det var möjligt att leda odlade laxsmolt till en önskad passage med hjälp av bubblor, strobeljus eller en kombination av bubblor och strobeljus. Med relativt enkla medel och låg kostnad konstruerades fiskledare som bestod av en perforerad slang driven av en luftkompressor samt en ljusramp med fyra LED-lampor vilka blinkade simultant med 480 bpm. Fem replikat genomfördes för vardera behandling, bubblor, strobeljus och bubblor/strobeljus, samt sex replikat i kontrollen. Under en timmes behandling fick tio laxsmolt, märkta med PIT-tag, passera en av två antenner, varav den ena var utrustad med en fiskledare, under vandring i nedströms riktning i ett strömakvarium. Denna studie visade att fiskledare av samtliga tre metoder ledde smolt till en önskad passage under behandlingens första femton minuter. Vidare visade fiskledaren bestående av bubblor en fortsatt ledande förmåga över hela behandlingsperioden (60 minuter), medan fiskledarna av strobeljus- och bubbel/strobeljus inte visade en sådan effekt. / Passages by fish through hydropower plants are associated with high mortality. In order to reduce the impact of hydropower plants on fish stocks, a variety of fish guiding systems have evolved. In this laboratory study, three types of non-physical fish guiding systems were evaluated by their efficiency in leading cultivated smolt of Atlantic salmon (Salmo salar L.) to a desired passage. This study aimed to answer if it is possible to guide salmon smolt to a desired safe passage by using bubbles, strobe light or a combination of bubbles and strobe light. With relatively simple means and low cost, fish-guides were constructed consisting of a perforated tube driven by an air compressor and a light ramp with four LED lights, which simultaneously flashed at 480 bpm. Five replicates were performed for each treatment; bubbles, strobe light and bubbles / strobe light, as well as six replicates for the controls. During one hour of treatment, ten salmon smolt, marked with PIT tag, could pass one of two antennas, where one had a fish-guide in front of the antenna, while migrating downstream in a stream aquarium. This study showed that fish-guides of all three methods led smolt to a desired passage during the first fifteen minutes of treatment. Furthermore, the bubble method showed a continuous guiding capacity throughout the treatment period (60 minutes), while the strobe light and bubble/strobe light did not show such an effect.