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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.

The behavior of organisms can affect their vulnerability to human induced selection, including recreational angling. Angling is expected to select fish with bold behavior, which may be linked to low stress responses through stress coping styles. Brown trout ( Salmo trutta ) is an intensively fished salmonid, and thus provides a relevant model to study artificial human-induced selection by angling. We used a selection experiment with fish possessing high or low vulnerability to angling to understand the consequences on traits related to stress coping styles and metabolic rate. We produced selection lines in two populations of brown trout –one wild and one reared in captivity for several generations- and reared the offspring in common garden conditions. We then assessed minimum and average metabolic rates, boldness and sensitivity to stress in juveniles at the age of 1 year. Angling selection had population-specific effects on risk taking-related latency and exploration tendency, and populations differed on average in several measured traits, which could be due to a combination of genetic and non-genetic effects. Our study provides evidence for angling induced selection in fish personality and suggests that metabolic rate and stress sensitivity might also be affected. The results can be explained by contrasting frequencies of proactive and reactive stress coping style in the two populations. Significance statement Hunting and fishing by humans, as any predation, can select individuals with bold behaviors, which potentially leads to an increase in shyness in prey populations. Because this is expected to occur in many fish stocks, we experimentally tested the consequences of angling vulnerability in brown trout in their offspring. Angling selection had different effects on a wild and a hatchery population of brown trout, making hatchery juveniles from low vulnerability parents more willing to take risks and have a faster metabolism than offspring from highly vulnerable parents, but having only a weak effect on in juveniles from the wild population. Our study implies that angling selection can lead to accumulating behavioral, stress sensitivity and metabolic change over time. Whether this will manifest in increased shyness may depend on the background of the population.

The conservation and management of endangered species requires information on their genetic diversity, relatedness and population structure. The main genetic markers applied for these questions are microsatellites and single nucleotide polymorphisms (SNPs), the latter of which remain the more resource demanding approach in most cases. Here, we compare the performance of two approaches, SNPs obtained by restriction-site-associated DNA sequencing (RADseq) and 16 DNA microsatellite loci, for estimating genetic diversity, relatedness and genetic differentiation of three, small, geographically close wild brown trout (Salmo trutta) populations and a regionally used hatchery strain. The genetic differentiation, quantified as F-ST, was similar when measured using 16 microsatellites and 4,876 SNPs. Based on both marker types, each brown trout population represented a distinct gene pool with a low level of interbreeding. Analysis of SNPs identified half- and full-siblings with a higher probability than the analysis based on microsatellites, and SNPs outperformed microsatellites in estimating individual-level multilocus heterozygosity. Overall, the results indicated that moderately polymorphic microsatellites and SNPs from RADseq agreed on estimates of population genetic structure in moderately diverged, small populations, but RADseq outperformed microsatellites for applications that required individual-level genotype information, such as quantifying relatedness and individual-level heterozygosity. The results can be applied to other small populations with low or moderate levels of genetic diversity.

A better understanding of the environmental and genetic contribution to migratory behavior and the evolution of traits linked to migration is crucial for fish conservation and fisheries management. Up to date, a few genes with unequivocal influence on the adoption of alternative migration strategies have been identified in salmonids. Here, we used a common garden set-up to measure individual migration distances of generally highly polymorphic brown trout Salmo trutta from two populations. Fish from the assumedly resident population showed clearly shorter migration distances than the fish from the assumed migratory population at the ages of 2 and 3 years. By using two alternative analytical pipelines with 22186 and 18264 SNPs obtained through RAD-sequencing, we searched for associations between individual migration distance, and both called genotypes and genotype probabilities. None of the SNPs showed statistically significant individual effects on migration after correction for multiple testing. By choosing a less stringent threshold, defined as an overlap of the top 0.1% SNPs identified by the analytical pipelines, GAPIT and Angsd, we identified eight candidate genes that are potentially linked to individual migration distance. While our results demonstrate large individual and population level differences in migration distances, the detected genetic associations were weak suggesting that migration traits likely have multigenic control.

Candidate genes associated with migration have been identified in multiple taxa: including salmonids, many of whom perform migrations requiring a series of physiological changes associated with the freshwater–saltwater transition. We screened over 5,500 SNPs for signatures of selection related to migratory behavior of brown trout Salmo trutta by focusing on ten differentially migrating freshwater populations from two watersheds (the Koutajoki and the Oulujoki). We found eight outlier SNPs potentially associated with migratory versus resident life history using multiple (≥3) outlier detection approaches. Comparison of three migratory versus resident population pairs in the Koutajoki watershed revealed seven outlier SNPs, of which three mapped close to genes ZNF665-like, GRM4-like, and PCDH8-like that have been previously associated with migration and smoltification in salmonids. Two outlier SNPs mapped to genes involved in mucus secretion (ST3GAL1-like) and osmoregulation (C14orf37-like). The last two strongly supported outlier SNPs mapped to thermally induced genes (FNTA1-like, FAM134C-like). Within the Oulujoki, the only consistent outlier SNP mapped close to a gene (EZH2) that is associated with compensatory growth in fasted trout. Our results suggest that a relatively small yet common set of genes responsible for physiological functions associated with resident and migratory life histories is evolutionarily conserved. peerReviewed

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Kalavarojen käyttö ja hoito pysyvät kestävällä pohjalla, kun päätökset perustetaan mahdollisimman luotettavaan ja ajantasaiseen tietoon. Tietoa tarvitaan toiminnan kaikissa vaiheissa, mutta erityisesti silloin, kun asetetaan tavoitetilaa ja osatavoitteita sekä myöhemmin, kun on aika arvioida toimenpiteiden tuloksellisuutta. Tässä luvussa esitellään alueelliseen käyttöön soveltuvia tiedonhankintamenetelmiä sekä annetaan ohjeita aineistojen keruuseen ja tulosten tulkintaan. nonPeerReviewed

Anssi Vainikka on väitöskirjassaan selvittänyt vaikuttavatko särjen ja suutarin ornamenttien tuottoon kytketyt hormonit niiden immuunipuolustuskykyyn. Vastoin ennakko-oletuksia, testosteronin tai estradiolin ei havaittu alentavan immuunipuolustuskykyä. Myöskään ornamenttien ja immuunipuolustuskyvyn mittareiden väliltä ei löytynyt seksuaalivalinnan teorioiden ennustamia positiivisia yhteyksiä. Korkea testosteronipitoisuus oli kuitenkin yhteydessä koirassuutarin hyvään kuntoon ja ornamentit kertovatkin koiraan hyvästä elinkyvystä. Testosterone is known to enhance reproductive success, but has also been proposed to suppress immune defence. Prior to spawning, male roach (Rutilus rutilus L.) produce testosterone-associated breeding tubercles those have been found to signal parasite load and parasite resistance. Tench (Tinca tinca (L.)) is sexually dimorphic throughout the year, and in addition to their large pelvic fins males produce ventral protuberances of unknown function during breeding. The indicator value of male tench ornaments, immunosuppressivity of testosterone, cortisol and oestradiol in roach and tench, and the level of stress during spawning in roach were studied. A study of crucian carp (Carassius carassius (L.)) aimed to link individual’s behavioural decisions to somatic growth, reproductive effort and future survival. In these studies, cortisol but neither testosterone nor oestradiol was found to have immunosuppressive effects. Neither did an immunological challenge decrease the concentration of testosterone. Although testosterone was positively related to the condition factor in tench, it was only weakly associated to the expression of male ornaments. High spawning-time prevalence of epidermal papillomatosis in male roach was suggested to result from sex-differences in spawning stress. Body depth gain in crucian carp was associated to growth in a manner dependent on predator presence, but the behavioural decisions of an individual did not correlate with measures of growth or reproductive effort. I suggest that stress steroids contribute to the honesty of sexual signalling in the studied cyprinids, whereas testosterone in both sexes may act as a condition-dependent hormone having a positive effect on sexual signalling and primary sexual traits, but being metabolically costly at high levels.

KORTET, RAINE, VAINIKKA, ANSSI, RANTALA, MARKUS J., TASKINEN, JOUNI (2004): Sperm quality, secondary sexual characters and parasitism in roach (Rutilus rutilus L.). Biological Journal of the Linnean Society 81 (1): 111-117, DOI: 10.1111/j.1095-8312.2004.00275.x, URL: https://academic.oup.com/biolinnean/article-lookup/doi/10.1111/j.1095-8312.2004.00275.x

Both the ability to gain a high dominance status and having an efficient immune defence are favourable qualities that typically increase fitness in social and host-parasite interactions. Individuals with a high dominance status are predicted to gain fitness-related benefits from prior access to limited, defensible resources, such as food and matings. Immune defence mechanisms, on the other hand, have evolved to minimize the fitness costs of parasitic infections. The relative significance of a high dominance status and strong immune defence for individual fitness is, however, affected by the quality of the environment. The aim of this thesis is to improve the understanding of environmentally determined variation in dominance status, immune defence and their consequences for individual fitness. I use the native noble crayfish (Astacus astacus), the invasive signal crayfish (Pacifastacus leniusculus) and the highly virulent, invasive Aphanomyces astaci, the causative agent of the crayfish plague, as my study models. I first experimentally test theoretical predictions on how major ecological factors, including food availability, predation risk and population density, influence behavioural decision-making in fight contests, especially with regard to the maintenance of dominance hierarchies between size-matched crayfish. Using natural noble crayfish subpopulations with different crayfish plague history, I then explore whether variation in immune defence and crayfish plague resistance is potentially explained by local adaptation to the disease, or alternatively by geographical divergence. By keeping noble crayfish experimentally under constant environmental conditions, I finally determine whether seasonal variation in immune defence is endogenously regulated. My results show that individuals that had achieved dominant status in non-resource fight contests have an advantage in monopolising a limited, defendable food resource in a future contest. Furthermore, I find evidence that as population density increases, the division of the resource between dominants and subdominants becomes more unequal. Generally, my results suggest that due to ecological factors the dominance status of individuals can be more dynamic than theory predicts, especially when the contestants have similar fighting ability. For example, in line with the asset-protection principle, individuals having achieved dominant status in a non-predation risk contest increase their submissive behaviours in the presence of a predation threat, giving subdominants the opportunity to win a larger percentage of bouts in the predation risk contest. My results also reveal evidence for geographical variation in resistance to the crayfish plague and immune defence that is, however, independent of historical disease outbreaks in the study subpopulations. Furthermore, for the first time in invertebrates, my results demonstrate reproduction-related endogenous seasonal variation in the immune defence of noble crayfish. Overall, my results suggest that ecological factors, such as population density, predation risk and disease history, have to be taken in to account to better understand the causes and consequences of dominance status and immune defence in any individual species. Korkea dominanssistatus sekä tehokas immuunipuolustus ovat ominaisuuksia, jotka tyypillisesti parantavat yksilön kelpoisuutta sosiaalisissa tilanteissa ja isäntä-loissuhteissa. Teoria ennustaa, että yksilöt joilla on korkea dominanssistatus pääsevät paremmin käsiksi kelpoisuutta lisääviin, rajallisiin ja puolustettaviin resursseihin, kuten ruokaan ja parittelukumppaneihin. Toisaalta, immuunipuolustuksen mekanismien ajatellaan kehittyneen pienentämään loisinfektioiden kustannuksia. Korkean dominanssistatuksen ja tehokkaan immuunipuolustuksen suhteellinen merkitys yksilön kelpoisuuteen riippuu ympäristön laadusta. Väitöskirjani tavoitteena on parantaa ymmärrystä siitä, miten ympäristö vaikuttaa dominanssistatuksessa ja immuunipuolustuksessa havaittavaan vaihteluun, ja näiden piirteiden vaikutuksiin yksilön kelpoisuudelle. Työssäni käytän Suomen luontoon kuuluvaa alkuperäislajia, jokirapua (Astacus astacus), sekä vieraslajia, täplärapua (Pacifastacus lenisculus), ja hyvin virulenttia rapuruttoa aiheuttavaa oomykeettiä (Aphanomyces astaci). Ensimmäiseksi testaan teorioita siitä, miten ekologiset tekijät (esim. ravinnon saatavuus, saalistusriski, populaatiotiheys) vaikuttavat yksilön päätöksentekoon taistelutilanteissa, etenkin suhteessa dominanssihierarkioiden säilyvyyteen silloin, kun vastustajat ovat samankokoisia. Toiseksi tutkin rapuruttohistorialtaan eroavilla jokiravun luonnonpopulaatioilla, voiko immuunipuolustuksessa ja rapuruton vastustamisessa olevaa variaatiota selittää paikallisella sopeutumisella tautia vastaan tai maantieteellisillä eroavaisuuksilla. Pitämällä jokirapuja kontrolloidussa ympäristössä selvitin onko kausiluonteinen vaihtelevuus immuunipuolustuksessa sisäisen kellon säätelemää. Tulokseni osoittavat, että yksilöt, jotka saavuttivat korkeamman dominanssistatuksen taisteluissa ilman resurssia, pystyivät monopolisoimaan rajoitetun, puolustettavan resurssin seuraavissa taisteluissa. Lisäksi osoitin, että populaatiotiheyden kasvaessa erot resurssien jaossa dominanttien ja subdominanttien yksilöiden kesken kasvavat. Yleisesti tulokseni osoittavat, että ekologisten tekijöiden vaikutuksesta yksilön dominanssistatus voi muuttua dynaamisemmin kuin perusteoria ennustaa etenkin, kun vastustajilla on samankaltaiset taistelukyvyt. Esimerkiksi asset-protection teorian mukaisesti yksilöt, joilla oli korkea dominanssistatus saalistajien puuttuessa, lisäsivät subdominanttia käyttäytymistä saalistajien läsnäollessa. Tällöin saalistusriskikokeissa alhaisemman dominanssistatuksen yksilöt saivat paremmat mahdollisuudet voittaa taisteluita. Tulokseni osoittavat myös, että rapuruton vastustamisessa ja immuunipuolustuksessa on maantieteellistä vaihtelua, jota ei voitu selittää tutkittujen osapopulaatioiden rapuruttohistorialla. Lisäksi osoitan ensimmäistä kertaa selkärangattomilla, että immuunipuolustuksen vaihtelu on kausiluonteista sisäisesti säädeltyä ja mahdollisesti kytköksissä lisääntymiseen. Yleisesti, tulokseni osoittavat, että ekologiset tekijät, kuten populaatiotiheys, saalistusriski ja tautihistoria, on otettava huomioon, jotta ymmärtäisimme dominanssistauksen ja immuunipuolustuksen yksilöllisiä syitä ja seurauksia paremmin.