Animals rely on lipids as a major fuel for endurance exercise because they pack more joules per gram than any other fuel. However, in contrast to mammals, information on how the mobilization of lipids from endogenous stores is managed to meet the needs of energy metabolism in swimming fish is sparse. Information on in vivo rates of lipid mobilization in swimming fish has been limited to relatively low exercise intensities and has only been investigated in a single species. Therefore, the goal of my thesis was to address this paucity of information by quantifying lipolytic rate in rainbow trout during graded exercise and fatty acid mobilization in Atlantic salmon during prolonged endurance exercise. In the first part of my work, I hypothesized that like mammals, rainbow trout stimulate lipolysis above resting levels to a peak with increasing work intensity, but subsequently lower its rate at high intensities when ATP production from carbohydrates becomes dominant. To test this hypothesis, I measured the rate of appearance of glycerol (Ra glycerol) in the blood (resulting from the breakdown of triacylglycerol (TAG)) of trout at rest (control) and during graded exercise from rest to Ucrit. Results showed that Ra glycerol in trout averaged 1.24 ± 0.10 µmol kg -1 min-1 and that this rate was unaffected by exercise of any intensity. These experiments revealed that rainbow trout do not modulate lipolysis during exercise. Furthermore, I calculated that baseline lipolytic rate was much higher in trout than in mammals and that this rate is in constant excess of the requirements of energy metabolism. My second investigation focused on measuring fatty acid mobilization in Atlantic salmon. To date, the majority of studies on energy metabolism in salmonids have used rainbow trout as the ubiquitous model for salmonids. I postulated that domesticated rainbow trout may be far less impressive athletes than their wild anadromous form and other salmonids. In this regard, I proposed that studying energy metabolism in Atlantic salmon (even those from aquaculture) may help to deepen our understanding of the physiology of true long-distance migrant fish. To study the effects of prolonged endurance exercise on the mobilization of fatty acids from endogenous stores in these fish, I monitored the rate of appearance of fatty acids (Ra NEFA calculated from Ra Palmitate) in the blood during 72 hours of sustained swimming. I found that contrary to what has been previously described in rainbow trout, Ra Palmitate (and by proxy, Ra NEFA) is reduced by approximately 64% (from 0.75 ± 0.12 µmol kg-1min-1 to 0.27 ± 0.06 µmol kg-1min-1 and from 19.3 ± 7.8 µmol kg-1min-1 to 6.9 ± 2.0 µmol kg-1min-1 for Ra Palmitate and Ra NEFA, respectively) during prolonged endurance exercise in Atlantic salmon. However, like in trout, even this reduced rate of fatty acid mobilization exceeds the requirements of energy metabolism at rest and during swimming. While further experiments will be necessary, I speculated that this reduction in Ra NEFA may be caused by a partial inhibition of lipolysis to reduce the energetic cost of TAG:FA cycling and optimize fuel budgets during prolonged endurance exercise. This thesis provides the first in vivo measurements of lipolysis during graded exercise in salmonids and the first in vivo measurements of fatty acid mobilization in Atlantic salmon. From the results mentioned above, I concluded that salmonids mobilize lipids in constant excess of the requirements for energy metabolism, possibly to allow for rapid reorganization of membrane phospholipids in response to changing environmental conditions. However, more anadromous and migratory phenotypes may rely on a tighter control of lipolysis to minimize the costs of substrate cycling and conserve energy on limited fuel stores.

The earth’s climate is rapidly changing. With climate change currently altering the environment, water temperature is an important environmental factor that will have various effects on fishes since they are ectotherms. As the changes are expected to be greatest during winter, when salmonid fishes incubate their eggs, one might expect substantial effects on egg development. In this experiment pairs of fish, matched by length, were compared. For each pair, one fish had experienced ambient cold temperatures (cold treatment) during embryogenesis and the other elevated temperatures (warm treatment, ca. 4-5 oC). The fish were tested in stream. Aggressive interactions were recorded and dominance was determined by scoring each fish’s position relative to where food was delivered from and the amount of food taken. Salmon from the cold treatment had a strong tendency to have a higher dominance score than salmon from the warm treatment. The individual with the highest dominance score was not consistently larger or smaller than the individual with the lower dominance score. The results support the hypothesis that salmonids exposed to a cold environment during embryogenesis will be more dominant. Due to climate change, it is expected that water temperature will continue to rise in the future, which in turn will alter the fish’s behaviour. / Jordens klimat förändras snabbt. Med klimatförändringar som för närvarande förändrar miljön är vattentemperaturen en viktig miljöfaktor som kommer att ha olika effekter på fiskar eftersom de är ektoterma. Eftersom förändringarna förväntas vara störst under vintern, när laxfiskar inkuberar sina ägg, kan man förvänta sig betydande effekter på äggutvecklingen. I det här experimentet jämfördes fisk par, matchade med längd. För varje par hade en fisk upplevt kalla vattentemperaturer (kall behandling) under embryogenesen och de andra förhöjda temperaturerna (varm behandling, ca 4-5 oC). Fisken testades i strömakvarie. Aggressiva interaktioner registrerades och dominans bestämdes genom att poängsätta varje fisks position i förhållande till var mat levererades från och mängden mat som tagits. Lax från den kalla behandlingen hade en stark tendens att ha högre dominanspoäng än lax från den varma behandlingen. Individen med högsta dominanspoäng var inte konsekvent större eller mindre än individen med lägre dominanspoäng. Resultaten stöder hypotesen att salmonider utsätts för en kall miljö under embryogenes kommer att vara den mer dominerande. På grund av klimatförändringen är det förväntat att vattentemperaturen fortsätter att stiga i framtiden, vilket i sin tur kommer att förändra fiskens beteende.

Pour comprendre l'origine des variations d'histoire de vie des organismes, il fautétudier et mettre en évidence les stratégies d'histoire de vie et les processus évolutifsqui les gouvernent. Ce travail de thèse a pour objectif d'étudier les stratégiesd'histoire de vie et leur conditionnement par les caractéristiques individuellesen conditions naturelles. Les stratégies d'histoire de vie sont vues comme un agencementde normes de réactions et de compromis évolutifs. Cependant, l'étude desprocessus évolutifs en milieu naturel se heurte à des problèmes d'ordre méthodologique.En effet, le suivi exhaustif au cours du temps d'individus d'une populationest difficilement réalisable, voire impossible en conditions naturelles. Les méthodesde capture-marquage-recapture permettent une observation partielle des histoires devie et des traits d'histoire de vie. Ce travail se base sur l'idée que nos observationsne sont que la partie visible de processus sous-jacents qu'il est nécessaire de prendreen compte pour ne pas biaiser nos inférences statistiques. J'utilise la modélisation àstructure cachée pour 1) séparer le processus d'observation du processus dynamiqued'intérêt, 2) modéliser les histoires de vie complètes des individus, 3) intégrer dansun cadre unique et cohérent les décisions d'histoire de vie et les compromis évolutifset 4) représenter explicitement les mécanismes sous-jacents qui génèrent nos observations.Dans ce cadre, on peut alors intégrer les théories et concepts de la biologieévolutive dans l'analyse statistique des données d'observations. J'illustre ce travailpar l'étude du conditionnement des stratégies d'histoire de vie dans une populationnaturelle de saumon Atlantique sur le Scorff (Morbihan) à partir de données de CMR.Mes résultats mettent en évidence des décisions d'histoire de vie statut-dépendanteset des compromis évolutifs qui n'auraient pas pu être mis en évidence hors du cadrede modélisation proposé. / Understanding the origin of life history variations of organisms requires studying life historystrategies and evolutionary processes that drive them. This thesis aims at studying life historystrategies under natural conditions and how they are conditioned by individual characteristics.Life history strategies are seen as a combination of reaction norms and evolutionarytrade-offs. The study of evolutionary processes in the wild faces to methodological issues.Indeed, the exhaustive monitoring of individuals over time is often impossible in the wild.Capture-mark-recapture methods allow a partial observation of life histories and life historytraits. This work was based on the idea that our observations are only the visible part ofunderlying processes that need to be accounted for to limit the risk of flawed statistical inferences.I resort to hidden structure modeling to 1) separate the observation process fromthe dynamic process of interest, 2) model the full life histories of individuals, 3) integratewithin a single and coherent framework life history decisions and evolutionary trade-offs and4) explicitly represent the underlying mechanisms that generate our observations. Withinthis framework, one can confront theories and concepts in evolutionary biology with observationaldata through appropriate statistical tools. Finally, I illustrate this work by studying theconditioning of life-history strategies in a natural population of Atlantic salmon on the Scorffriver (Morbihan) using CMR data. My results highlight status-dependent life history decisionsand evolutionary trade-offs that could not be identified without our proposed modelingframework.

Under hösten leker en inhemsk population av Atlantisk lax (Salmo salar) i Klarälven, Sverige, för att därefter vandra nedströms tillbaka till sjön Vänern. Vid älvens andra kraftverk sett från Vänerns mynning, Dejefors kraftverk, finns det planer på att ersätta ett av kraftverken mot ett nytt och det finns därför ett behov av att ta reda på hur laxens nedströmsvandring påverkas av det kraftverket som finns där i dag. Då alla kraftverk i Klarälven saknar fiskpassagelösningar är det extra viktigt att följa upp laxarnas passageöverlevnad under vandringen. Avsikten med denna studie var därför att ta reda på hur laxen rörde sig runt kraftverket, hur väl de klarade av att passera kraftverket beroende av vilken passageväg de tog och vilka faktorer som påverkade passageframgången. Under september 2020 fångades 40 laxindivider in när de var på väg uppströms inför leken. De mättes och märktes med telemetrisändare för att sedan transporteras uppströms och släppas ut nedanför kraftverket i Munkfors, varifrån deras nedströmsvandring förbi Dejefors kraftverk följdes och analyserades med hjälp av akustisk telemetri. Resultatet visade att det inte fanns någon signifikant skillnad mellan kön för när laxarna påbörjade sin nedströmsvandring. Kraftverket visade sig dock fördröja laxarnas nedströmsvandring då det tog längre tid för dem att passera kraftverket än vad det tagit dem att simma ner dit i den fritt strömmande delen av älven. Av de 31 laxar som anlände till Deje så passerade 27 av dem kraftverket, varav 13 individer överlevde (48 %). Överlevnaden var högre för individer som passerade via spillutskoven (10 av 12) än turbinerna (3 av 15). Det fanns en signifikant skillnad i mortalitet vid kraftverkspassage beroende på laxens längd och passageväg; långa individer hade en högre mortalitet (73 %) än kortare (25 %) och passagevägen hade en signifikant effekt på mortaliteten. Resultatet visar tydligt på ett behov av åtgärder för att förbättra överlevnaden hos lax vid passage av Dejefors kraftverk. Lösningar för att få fisken att helt undvika turbinerna och istället välja en annan passageväg vore troligen den bästa och effektivaste lösningen för att öka laxens överlevnad under nedströmsvandringen. / During autumn, the endemic Atlantic salmon (Salmo salar) migrate upstream to spawn in the river Klarälven, Sweden, after which they migrate downstream back to Lake Vänern. There are plans to remove one of the power houses in Deje, and replace it with a new power house, and before that happens it is important to study the downstream passage conditions at the site. As all power plants in Klarälven lack fish passage solutions, it is important to follow up the salmon passage survival during the migration. The purpose of this study was therefore to study how downstream migrating salmon negotiate the power plant, the route-specific passage survival and what factors that could affect their passage success. In September 2020, 40 upstream migrating salmon individuals were caught, measured and tagged after which they were transported and released below the power plant in Munkfors. Their downstream migration past Dejefors power plant was studied and analyzed using acoustic telemetry. The results showed that there was no significant difference between sexes in regards of downstream migration timing. However, the power plant turned out to delay downstream migrating salmon as it took longer time for them to pass the power plant than it took them to swim down the free-flowing part of the river. Of the 31 salmon that arrived in Deje, 27 passed the power plant, of which 13 individuals survived (48%). The survival rate was higher for individuals passing via spillways (10 of 12) than turbines (3 of 15). There was a significant difference in mortality rate at power plant passage depending on the length and passage route of the salmon. Large individuals suffered a higher mortality (11 of 15) than short (3 of 12) and a larger proportion of the salmon died when passing through the turbines than through spill gates. Based on the results, there was a clear need for improved survival rates for salmon passing the Dejefors power plant. The design of the turbines could be changed for increased survival, but at the same time other solutions that will make it possible for fish to avoid the turbines and instead choose another passageway would probably be a better and more efficient solution to increase the survival of the salmon during their downstream migration.

There is a concern that the ecosystems around the world are suffering from fragmentation. Ecosystems such as rivers have lost their connectivity to a large extent due to hydroelectric dams with no or insufficient passways for the natural flow of organisms, matter and energy. The Atlantic salmon, Salmo salar, is anadromous, migrating up rivers to spawn as adults and downstream to the sea as juveniles to feed. Before entering the sea, juveniles go through a parr-smolt transformation which alters their behavior, morphology, and physiology. Using radio telemetry, we assessed how the degree of smoltification, in combination with migrational timing and the juvenile’s size, affected their migration. Overall migratory success was found to differ significantly across the range of smoltification, with more fully smoltified juveniles having the highest probability (94%) of reaching the sea. No relationship was found between smoltification status and average migrational speed or delays when passing a dam. Migrational timing was also correlated to migrational success, with earlier juveniles being 50 % more likely to reach the sea than those leaving 2-3 weeks later. All of the tagged juveniles (28) that passed the dam were delayed by an average of 1,32 km/h relative to their median speed in the river, and 18 of the juveniles made it down to the sea. No effect of migrational timing was found with average migrational speed or with dam delays however. Unexpectedly, larger lengths were correlated with slower average migration speeds and greater delays when encountering a dam. This new knowledge about the degree of smoltification and its relation to migration success can help river management to direct their efforts in the right direction to strengthen salmon populations. / Ekosystem som älvar och åar har i stor utsträckning förlorat konnektiviteten till följd av vattenkraftverk med otillräckliga passager för det naturliga flödet av organismer, materia och energi. Atlantlax Salmo salar är en anadrom fisk vars livscykel kräver att den vandrar mellan olika habitat. Den vandrar upp i vattendrag som vuxna för att leka och ut till havet som unga för att äta. De unga laxarna går igenom en utvecklingsprocess (smoltifiering) innan de simmar ut i havet vilket förändrar deras beteende, morfologi och fysiologi. Med hjälp av radiotelemetri bedömde vi hur graden av smoltifiering i kombination med timing och storlek påverkade deras nedströmsvandring. Vi såg en avsevärd skillnad inom dem olika smoltifierings graderna och en lyckad nedströmsvandring, de fullständigt smoltifierade fiskarna var mest sannolika att klara nedströmsvandringen (94%). Inget samband hittades mellan smoltifieringsgrad och genomsnittliga vandringshastigheten genom ån eller förbi ett vattenkraftverk. En lyckad nedströmsvandring var relaterad till tid och vi fann att de som vandrade tidigt hade 50% större chans att nå ut till havet än de som lämnade 2–3 veckor senare. Alla radiomärkta fiskar (28) som passerade vattenkraftverket vart försenade med -1,32 km/h jämfört med deras genomsnittliga hastighet, av 48 märkta fiskar klarade sig 18 ut till havet. Oväntat nog var längre längd relaterat till större förseningar både i medianhastighet och vid passage av en damm. Den här kunskapen om sambandet mellan smoltifieringsgrad och lyckad nedströmsvandring kan förbättra insatser som görs i åar och älvar för att optimera för djur och natur.

Vattenkraften har en negativ miljöpåverkan på flera sätt, inte minst genom fragmentering av vattendrag. Därför är det viktigt att studera åtgärder som potentiellt minskar vattenkraftens inverkan. Här undersöktes experimentellt avledningseffektivitet och tidsåtgång för nedströmsvandrande atlantlaxsmolt hos låglutande avledare i en strömränna. Smolten startade uppströms om anläggningen och registrerades ifall de besökte flyktöppningarna i passagelösningen för nedströmsmigrerande fisk. Inom båda huvudtyperna, α- och β-avledare, testades tre olika avledare vardera där α-avledarna bestod av galler med spaltvidderna 15, 18 och 30mm. β-avledarna innefattade två galler med spaltvidderna 15 och 30 mm samt ett kevlarnät med entumsmaskor. Resultaten visade att hos α-avledare hade spaltvidden hos gallret betydelse för effektiviteten mellan största och minsta gallret. Mellan β-avledarna med 15 och 30 mm spaltvidd hade spaltvidden ingen betydelse varken för avledningseffektivitet eller tid till passage. Däremot var entumsnätet mindre effektivt. Resultaten indikerade att β-avledare var generellt mer effektiva än α-avledare med högre avledningseffektivitet, möjligen på grund av olikheter i konstruktionerna av flyktöppningarna i anslutning till avledarna. Resultatet pekar också på att β-galler kan ge upphov till en beteenderespons hos smolten som inte registrerades hos α-galler. / Hydropower has a negative environmental impact in several ways, not least through fragmentation of watercourses. This makes it important to study measures that potentially reduce the impact of hydropower. Here, diversion efficiency (passage) and time spent migrating by Atlantic salmon smolts was tested experimentally in a flume equipped with low-slope diverters, simulating passage of a hydropower plant. The smolt were released upstream of the facility and were registered if they visited the entrance to the flume’s passage solution for downstream migrating fish. In both main types, α- and β-diverters, three different diverters were tested each, where the α-diverters consisted of bar racks with gap widths of 15, 18 and 30mm. The β-diverters included two bar racks with gap widths of 15 and 30 mm and a kevlar net with 25 mm meshes. The results showed that in α-diverters, the gap width of the racks was important for the efficiency between the largest and smallest gap widths. Between the β-diverters with 15- and 30 mm gap width, the gap width had no significance either for efficiency or time to passage. However, the one-inch net was less efficient. The results indicated that β-racks were generally more efficient than α-racks with higher diverting efficiency, possibly due to differences in the constructions of the escape openings adjacent to the diverters. The result also suggests that β-racks may give rise to behavioral responses in the smolt that was not registered in α-racks.

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Univ., Diss.--Trier, 2004. / Literaturverz. S. 355 - 379.