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The landlocked salmon (Salmo salar m. sebago) endemic to Lake Saimaa, Finland, is critically endangered and severely threatened by low genetic diversity and inbreeding. To explore the possibility of increasing the genetic diversity of threatened salmon populations by controlled hybridization (genetic rescue), we studied sperm motility and offspring pre- and posthatching survival in hybridization crosses of landlocked salmon with two geographically close anadromous salmon populations (Rivers Neva and Tornio) relative to the pure-bred populations. While some degree of gametic incompatibility between landlocked and Tornio salmon cannot be ruled out, there were no indications of outbreeding depression in survival traits in these first-generation hybridizations. Instead, prehatching survival of landlocked salmon eggs fertilized with Neva salmon sperm and posthatching survival of anadromous salmon eggs fertilized with landlocked salmon sperm were higher than survival in pure-bred landlocked salmon. These differences might imply genetic rescue effects (hybrid vigor), although there were also strong maternal effects involved. Our results on early viability point to the possibility of applying genetic rescue to the landlocked salmon population by hybridization with an anadromous population.

Certain spawning areas of the critically endangered Lake Saimaa landlocked Atlantic salmon (Salmo salar m. sebago) have been recently restored by excavator- and helicopter-scattered gravel, but the success of applied methodologies has remained open. Here, we monitored the spawning-related movements and redds occurrence of transported semi-wild and hatchery-reared salmon in the restored River Ala-Koitajoki, eastern Finland, using radiotelemetry and snorkeling. Nearly all fish accepted the newly restored spawning habitats in the river that maintains a low flow rate (only 4 m3·s−1). The movements of females released up to 2 weeks before spawning time were restricted mainly to the closest rapids from the release site, and most of the movements were directed downstream. Semi-wild and hatchery background fish exhibited similar mobility, which was more variable among males. A majority of redds were found in restored areas, and both helicopter- and excavator-scattered gravels were accepted as spawning substrates. Our results indicate that natural reproduction of the studied landlocked salmon population can be successfully returned to its original spawning river by restoration of habitats and transfer of spawners.

Several Finnish populations of salmonids have been maintained exclusively by stocking hatchery-reared fish for several generations, and it is crucial to know whether domestication has affected fitness-related traits and to assess how the developmental environment influences fish phenotypes. Here, we focused on Lake Saimaa landlocked salmon (Salmo salar m. sebago) and studied the role of the early rearing environment in trait formation by comparing juveniles (fingerlings) from three backgrounds: (i) semi-wild (stocked as alevins), (ii) standard hatchery, and (iii) enriched hatchery conditions We compared juvenile morphology, swimming performance, and capability of feeding on natural prey in early winter. We found no differences between standard and enriched hatchery conditions. Semi-wild fish consumed more prey items, but wet mass of stomach contents did not differ among backgrounds. Swimming endurance was comparable among backgrounds. Semi-wild fish had slenderer body shape and longer fins than hatchery-reared fish. The lack of performance differences between hatchery juveniles and their semi-wild conspecifics is possibly due to reduced phenotypic plasticity caused by extremely low levels of genetic diversity in this population.

Nonanadromous Atlantic salmon (Salmo salar) exhibit a combination of variation in life history, habitat, and species co-existence matched by few vertebrates. Distributed in eastern North America and northern Europe, habitat ranges from hundreds of metres of river to Europe’s largest lakes. As juveniles, those with access to a lake usually migrate to feed and grow prior to reproduction. Prey such as smelt (Osmerus mordax, Osmerus eperlanus) and vendace (Coregonus albula) facilitate large body size (50–85 cm at maturity) and persistence in high-diversity (>20 fish species) environments; small-bodied salmon (10–30 cm at maturity), relying on insects as prey, coexist with few (fewer than five) other fishes. At maturity, weight varies more than 400-fold (17 to 7200 g) among populations, fecundity more than 150-fold (33 to 5600), and longevity almost fivefold (3 to 14 years). Landlocked salmon are managed to support sustainable fishing, achieve conservation and restoration targets, and mitigate threats; successes are evident but multiple challenges persist. Extraordinary variability in life history coupled with extensive breadth of habitat and species co-existence render landlocked Atlantic salmon singularly impressive from a biodiversity perspective.

Through the recent increases in abundance, pikeperch (Sander lucioperca) has not only become a valuable target for recreational and commercial fishing, but also the most important top predator in many lakes. Generally oligotrophic Lake Hoytiainen (283 km²) sustains one of the most economically valuable pikeperch stocks in Finland, and its annual fisheries yield (up to 5.5 kg/ha) is exceptionally high among Finnish lakes. Here, we followed seasonal movements of fish using conventional tagging, and studied short‐term and long‐term diet of pikeperch by stomach content and stable isotope analyses to examine if the movements were motivated by prey availability. A clear seasonal migration pattern was observed: in summer, 80% of the tag recoveries were obtained from the shallow and mesotrophic northern and western areas, whereas in autumn and winter, the deep and oligotrophic southern area dominated in the recaptures. The diet of pikeperch consisted of the most abundant fish species in the lake, perch (Perca fluviatilis) and roach (Rutilus rutilus), as well as insects. Stable isotope analysis indicated a shift from a dominance of pelagic food sources to littoral food sources during the growing season of pikeperch. Our results suggest that the pikeperch migrations facilitate efficient material transfer from the mesotrophic part while the deeper and oligotrophic part offers a favourable overwintering environment.

Although hybridization between populations with low genetic diversity may induce heterosis, it can also lead to reduced fitness of hybrid offspring through outbreeding depression and loss of local adaptations. Using a half-sib mating design, we studied on brown trout (Salmo trutta) how hybridization of migratory hatchery-strain females with males from various strains would affect early mortality, growth and personality in F1 offspring. No differences in mortality or alevin body length were found between the crossing groups by the end of the yolk-sac stage. At later developmental stages, higher mortality and slower growth in one of the geographically distant hybrid groups indicated potential outbreeding depression. The personality component indicating boldness and exploration tendency showed fairly low genetic variation and no phenotypic differences among the crossing groups while the personality component related to freezing behavior indicated stronger freezing responses in the purebred and local cross strain when compared to the two other strains. However, the purebred hatchery strain possessed stronger additive genetic tendency for boldness and explorative behavior, and weaker genetic tendency for freezing behavior, when compared to the wild × hatchery hybrid group. Our results add to the cumulating evidence of risks related to the stocking of fish strains from non-native origins.

Enriched rearing has been demonstrated to shape the phenotype of hatchery-reared salmonids and improve their post-release survival in the wild, thus having an important applied value in conservation. However, it is unclear if rearing conditions or survival selection during the early life stages induce long-term fitness effects on adult phenotypes. Using a paired full-sib set-up, we investigated the influence of the environmental enrichment at the egg and fry stages on the milt quality and skin colouration of the adult brown trout (Salmo trutta L.). Overall, males had a higher number of skin spots than females. Notably, the total numbers of spots and black spots were significantly lower in fish raised in an enriched environment than in their full siblings reared in a conventional hatchery environment. However, neither sperm motility nor sperm swimming behaviour differed between full sib males reared in different environments. Our results suggest that rearing method may shape the colouration of brown trout, either by ecological carry-over effects or by selective survival during the rearing process. This, in turn, indicates that ecological conditions at early life can have long-prevailing phenotypically plastic or microevolutionary effects on the adult traits of fish. These effects should be taken into consideration to better understand the ecological role of rearing methodology in salmonid conservation.

Supplementing endangered fish populations with captive bred individuals is a common practice in conservation management. The aim of supplementary releases from hatchery broodstocks is to maintain the viability of populations by maintaining their genetic diversity. Landlocked Lake Saimaa salmon (Salmo salar m. sebago) has been critically endangered for the past half-century. As a result of anthropogenic disturbance, especially construction of hydroelectric power plants, the Lake Saimaa salmon has become completely dependent on hatchery broodstock. Recently, habitat restoration has been done in one of the former spawning rivers with the aim of creating a new natural spawning ground for the critically endangered population. Hatchery fish releases have also been revised so that in addition to juveniles, adult fish from the hatchery and from the wild have been released into the restored river. We assessed here if a restored river stretch can be used as a natural spawning ground and juvenile production area with the aim of improving genetic diversity of the critically endangered Lake Saimaa salmon. By constructing a pedigree of the released adults, and juveniles sampled from the restored river, we found that the majority of the released adults had produced offspring in the river. We also found that wild-caught spawners that were released into the restored river had much higher reproductive success than hatchery-reared parents that were released into the restored river at the same time. We found no significant differences in genetic diversity between the parent and offspring generations. Meanwhile, relatedness among different groups of adults and juveniles varied a lot. For example, while the hatchery-reared females were on average half-siblings, wild-caught females showed no significant relatedness. This highlights the importance of using pedigree information in planning the conservation and management of endangered populations, especially when artificial propagation is involved.

Composition of membrane lipids from the gills of juvenile Atlantic salmon (Salmo salar) in presmolt and smolt phases of development was compared among anadromous and non-anadromous populations. Three stocks migrating from spawning rivers to either lake (landlocked stock), brackish water or full strength sea water were grown under common garden conditions, and gill lipids and their acyl and alkenyl chains were examined in February (presmolts) and at the end of May (smolts) by mass spectrometry and gas-liquid chromatography. The most remarkable changes upon transition from the presmolt phase to the smolt phase were: (i) increase in the cholesterol/phospholipid ratio, (ii) decrease in the abundance of phosphatidylinositol (PI) content, (iii) increase in the amount of sulfatides, (iv) increase in phosphatidylcholine (PC) and phosphatidylethanolamine (PE) species with two highly unsaturated acyl chains, and finally (v) convergence of interstock differences in PC and PE species composition towards a similar lipid composition. Increases in the gill membrane content of cholesterol and sulfatides are discussed as pre-adaptation of salmon gills for salt-secretion, which may occur by increases in membrane microdomains (rafts) harboring ion channels and pumps. The decreases of PI were likely related to adjusting the gill membrane permeability to ions by diminishing prostanoid production. The similarity of those changes among three salmon stocks and the convergence of initially (presmolt phase) different PC and PE species profiles between the stocks towards similar lipid composition suggests that smoltification process of the gill epithelium is largely similar in anadromous and landlocked populations.

Animal personalities (sometimes referred also as coping styles) and their fitness consequences are currently among the most intensively explored subjects in behavioral ecology. To estimate the evolvability and adaptability of individually consistent behavioral variation, there is a crucial need to quantify the genetics underlying personality. Here, we experimentally studied the repeatability of various individual behaviors and then estimated heritability of formed boldness, exploration, and aggression components in juvenile brown trout Salmo trutta in standardized laboratory environment. Principal component analysis indicated that individually recorded behaviors were described by two personality axes: the first reflecting boldness, exploration, and aggression and the second tendency to freeze. These personality components, as well as the originally recorded behaviors, were statistically significantly repeatable over time. The latter PC, but not the first one, was statistically significantly heritable, though at low level (h 2 = 0.142 ± 0.096). These results suggest that additive genetic variation underlies phenotypically consistent behavioral patterns, proposing that any selection acting on behavior, stress tolerance, or correlated traits has a potential to induce evolution in fish personality.

We compared smolt physiology of Atlantic salmon stocks, that migrate from freshwater stream environments to a freshwater lake (Lake Saimaa, Finland), from the Neva River (Russia) to the brackish water of the Baltic Sea, and from the Teno River (Finland/ Norway) to the full-strength seawater of the Arctic Ocean. The three fish stocks were reared under common garden conditions, and ion homeostasis, seawater tolerance, activities of gill and kidney Na,K-ATPase and [3H]ouabain binding of gill and kidney tissues were determined at different phases of smoltification. Activity of gill Na,K-ATPase and number of gill [3H]ouabain binding sites reached peak values in May and were strongly suppressed in July. Osmolality and Na+, Cl-, and Mg2+ ion concentrations of blood plasma decreased during smoltification. αla and αlb isoforms of gill Na,K-ATPase decreased and increased, respectively, during smoltification. Although small differences appeared at some points in time, the seasonal pattern and magnitude of changes in...

We examined whether gene expression in the young salmon (Salmo salar) gill differs in relation to the salinity of their migration habitat by comparing three salmon stocks: (1) fish that migrate from a river system to Lake Saimaa, (2) fish that migrate to the brackish waters of the Baltic Sea, and (3) fish that migrate to the full-strength salinity of the Arctic Ocean. Transcripts of the gill tissue were measured at three successive developmental stages (parr, smolt and postsmolt) using the cDNA microarray in fish reared under common conditions. The changes in gene expression were qualitatively and quantitatively similar in the three stocks irrespective of the salinity of the natural growing habitat. This suggests that the parr—smolt transformation in the gill tissue of the landlocked fresh-water salmon stock is similar to the seawater migrating salmon. The transformation of the gill to a hypoosmotic organ in the freshwater salmon has been retained in evolution, possibly due to its adaptive role as a signa...

In the Koitajoki River, Eastern Finland, there exists a self-sustaining population of river-spawning densely rakered whitefish (Coregonus lavaretus pallasi). The population has been classified as near-threatened due to overexploitation and possible hybridization with the lake-spawning sparsely rakered whitefish form. Thus, knowledge of habitat use, movements, and migrations is important for threat assessment and management decisions. We employed conventional tagging and acoustic telemetry to provide information on movements and home range of the Koitajoki River whitefish. We tagged mature individuals at their spawning areas and followed fish movements by tag recoveries and continuously recording fixed receiving stations. The maximum movement distances were 40–50 km both upstream and downstream from the releasing site. There were indications of a clear seasonal migration pattern and spawning-site fidelity; riverine habitats were mainly occupied for spawning and overwintering, while feeding and growth mainly took place in lacustrine environments within several lakes of the river system. Due to their migratory nature, whitefish is vulnerable to environmental disturbances and overfishing in a large geographic area.

The hatchery environment often favours completely different traits than natural selection in the wild. Consequently, hatchery-reared fish are usually larger and more aggressive than their wild counterparts. Increased growth rate and aggression are predicted to be beneficial in feeding competition in hatcheries, but not necessarily in nature, where food resources are spatially and temporally more variable. We compared the growth, condition and mortality of landlocked Atlantic salmon (Salmo salar L.) juveniles in a common hatchery environment and when feeding on natural prey in semi-natural channels. We found that the growth and survival probability of the fish in the hatchery was negatively associated with their performance in the semi-natural channels. Furthermore, we found tendencies for directional selection (linear selection differential and gradient: P

Female mate choice is considered an important evolutionary agent, but there has been an ongoing debate over the fitness consequences it produces, especially in species that have a resource-free mating system. We examined a potential fitness benefit resulting from the pre-spawning mate preference in Arctic charr Salvelinus alpinus, a salmonid fish with no parental care. The females were first allowed to discriminate behaviourally between two males presented to them in a free choice test. We then tested with controlled fertilizations whether the females would accrue indirect genetic benefits for their offspring, as measured by embryonic viability, if they had mated with the male they preferred. Both parental identities influenced offspring survivorship, but the females did not consistently prefer the male which gave her the higher reproductive success. Neither was the degree of male red breeding coloration associated with female preference or the observable genetic quality. In contrast, there was a negative relationship between female coloration and her offspring survivorship, suggesting a significant trade-off in resource investment between sexual ornamentation and reproduction. To conclude, the potential indirect fitness consequences arising from females' pre-spawning mate preference seem to be negligible in early stages of development of Arctic charr.

Genetic theories of sexual selection predict that most ornamental secondary sexual traits provide reliable indication of the genetic quality of their bearers. Accordingly, also the offspring of mates with elaborate mating display should perform better than those of less conspicuous counterparts. In this study, we used Arctic charr (Salvelinus alpinus) as a model species to investigate whether the variation in a carotenoid-based red breeding coloration (a sexually dichromatic trait) in different sexes would reflect differences in individual genetic variability, one measure of individual quality, and/or indirectly, be manifested in variation in the offspring’s early viability and growth. We created maternal half-sibling families by artificially fertilizing the eggs with milt from bright- and pale-coloured males and then held the resulting progenies under identical hatchery conditions. The expression of red coloration among parental fish was not associated with their genetic diversity estimates in either sex nor did offspring sired by bright males consistently differ in terms of embryo survival or endogenous growth efficiency from offspring sired by pale males. By contrast, maternal effects were notably strong and, additionally, the degree of female coloration was negatively linked to their reproductive potential. The more intensely coloured females had a smaller relative fecundity and they also produced offspring of lower viability, implying a significant trade-off in resource allocation between ornamentation and offspring. Our results indicate that the red breeding ornamentation of Arctic charr is likely to be informative rather among females than males when the reproductive quality is predicted on grounds of the number of offspring produced. Nevertheless, this study does not support the direct selection hypothesis in explaining the evolution of female ornamentation, but rather suggests that the less intense coloration of female charr compared to males may reflect inter-sexual differences in the trade-off between natural and sexual selection.

Arctic charr are characterized by an extensive variability in growth and body size in natural waters. Although growth traits may involve a significant heritable component, most of this intraspecific variation presumably is environmentally induced and thus attributable to phenotypic plasticity. In the present study, size-at-age and length–weight relationship (body condition) were assessed for three Finnish Arctic charr populations of different geographical origins and extreme size forms (a stunted vs. two large-growing, predatory charr) held under standardized rearing conditions for 3 years (up to 37 months after hatching). In particular, our interest was to investigate whether the differences in growth between the large and the stunted charr as observed in the wild populations would diminish when the fish are offered suitable food in abundance. Population-specific mean body size and condition differed significantly in 0+, 1+, 2+ and 3+ fish. However, the identical rearing conditions resulted in the originally stunted charr reaching a comparable final mean size (317 mm/427 g) as the large charr populations (343 mm/510 g and 359 mm/497 g). Some individuals were of the same size as their parents at spawning already at the age of 0+ years. Furthermore, length–weight regression residuals of the stunted charr developed to a notably high level, indicating the largest final condition mean. The increase of size variation (CV of weight) in stunted charr lasted for over two growth seasons, whereas in large charr it remained stable since the end of the first summer. Variations in mortality and sexual maturation at age 2 seemed to be less relevant factors affecting overall growth performance. The study demonstrates an example of the high plasticity involved in the growth of fish: the stunted charr possess a tremendous capacity for growth in a benign environment, virtually corresponding to that observed in the large predatory populations.

Parasites cause significant economic losses in fish farming, and knowledge of the mechanisms underlying their effects on hosts is an essential prerequisite of preventative procedures for the parasite problem in hatcheries. One such mechanism is local adaptation of parasites, which should lead to higher infectivity of parasites in sympatric host–parasite combinations compared to corresponding allopatric combinations. In this study, we investigated the infectivity of two ubiquitous species of trematode eye flukes, Diplostomum sp. and Tylodelphus clavata, in their farmed salmonid fish hosts with respect to origin of the parasite and the host. First, we exposed two anadromous and one landlocked Atlantic salmon (Salmo salar) populations to controlled infection by Diplostomum sp. and natural infection by T. clavata. The anadromous salmon populations were local to Diplostomum sp. and non-local to T. clavata. In the case of the landlocked salmon, the population was non-local to Diplostomum sp. and local to T. clavata. Second, we exposed a landlocked population of Arctic charr (Salvelinus alpinus) to Diplostomum sp. cercariae from one non-local and two local parasite populations. The results indicated that eye fluke infectivity in both Atlantic salmon and Arctic charr was 1.5–2.6 times higher in local parasite–host combinations compared to those separated by greater geographical distance. This suggests that diplostomid parasites are able to adapt to local host populations, which may have significant implications such as high abundance and prevalence of the parasites in endangered fish stocks that are maintained in hatcheries.

Dominance status was determined among groups of four fish by using individuals from eight brown trout Salmo trutta populations. Subsequent growth of the fish was later recorded in larger groups. Seven months after the first set of trials, an additional set of dominance trials was performed by using the same fish. Social status affected subsequent growth; individuals having the lowest ranks grew less when compared to the higher ranking fish. Furthermore, the short term dominance hierarchy was rather stable between the two trials. This was especially the case with the lowest ranking fish, which tended to remain in the lowest position also in the second trial. The results suggest that the short term dominance trials done among few conspecifics reflect relatively well not only the subordinates' relative but also absolute social status.

– The morphology of three lake-resident Arctic charr, Salvelinus alpinus, populations was studied at two life-history stages in a common-garden experiment. The fish of the same year class were reared under standard hatchery conditions, and 27 morphometric variables (a truss network) were measured from the sampled individuals. Most of the total variation was explained by the overall body robustness, dimensions of the head and caudal peduncle length. After controlling for a body size, significant heterogeneity in body shape was found among populations at both ages. Independent of age, the populations were morphologically highly distinct, although some integration of characters could be found as the fish reached sexual maturity. Sexual divergence accounted for a large part of the within-population shape variation, the mature males having more robust bodies, larger head dimensions and longer pectoral fins compared with the mature females/immature fish. Although the cultured fish may not be totally representative of their wild counterparts, it is reasonable to expect that the observed morphological differences have a genetic basis, presumably reflecting adaptation to local environmental conditions experienced by the charr in their original habitat.

Standard metabolic rate (R(S)), specific growth rate (G) and aggressiveness were investigated in three Finnish populations of Atlantic salmon Salmo salar (Neva, Saimaa and Teno), which were reared in identical hatchery conditions. The populations differed in their geographical origin and native habitat. There was a significant difference between populations in R(S): the southernmost Neva population had higher values in R(S) than the northernmost Teno population. No difference was found in G or aggressiveness between the populations. G was found to have a significant positive association with aggressiveness and R(S) among the three populations, however, these results were not statistically significant after correction for multiple tests. There was no significant association between R(S) and aggressiveness. Higher metabolic rate of the most southern population Neva is suggested to be an adaptation to the more abundant food sources of the southern stream.

The connection between standard metabolic rate (RS) and parasite-induced cataract was investigated in this study. Oxygen consumption rate and cataract of 1 year-old fish in three Atlantic salmon Salmo salar stocks: Lake Saimaa, River Neva and River Teno reared at the same fish farm were examined. The measurements were carried out in winter, in spring before transporting the fish to the outside raceways and in autumn after the raceway period. Fish were exposed to natural Diplostomum spp. infection especially during the raceway period. The prevalence of cataract-bearing fish and cataract intensities (IC) differed between the populations. Most cataract-bearing individuals were found in the Saimaa stock and, in addition, the Saimaa stock had higher IC than Neva and Teno stocks. These findings support the theory of a parasite being most infective to local population. The RS, however, differed also between the stocks, the Teno stock had higher values compared to the Neva stock in winter. Furthermore, RS and cataract intensity had a statistically significant positive correlation in autumn. Therefore, the results also reveal a possibility that parasite infection affects RS of the fish. # 2008 The Authors Journal compilation # 2008 The Fisheries Society of the British Isles

Many populations of brown trout are managed by hatchery breeding and supportive release. Using a limited number of individuals as founders creates a bottleneck, which can lead to loss of genetic diversity in a population. In this study 17 populations of hatchery-reared brown trout were examined genetically using microsatellite markers. Genetic variation measured as gene diversity and allelic richness were analysed and the effects of effective population size of founders and time since founding on these parameters were explored. Allelic richness and gene diversity decreased with increasing time since founding of the stock, and there was a negative relationship between current effective population size and time since founding. Allelic richness was positively correlated with effective population size at founding. The results indicate that considerations concerning effective population size in hatcheries must be taken seriously to promote high levels of genetic variation among individuals and minimise loss of genetic diversity.

The metabolic rate (specific heat output) of individual eyed-stage eggs of Arctic charr Salvelinus alpinus (Linnaeus, 1758) originating from different families was measured with direct microcalorimetry. Metabolic rates varied between 2.3-7.9 microW ind(-1) and 0.06-0.22 microW mg(-1). Absolute heat output was unrelated to egg size, but size-scaled or specific heat output was negatively correlated with egg size, measured as diameter, dry mass or fresh mass. Metabolic rates varied significantly between families, suggesting that genetic and/or maternal effects affect embryonic metabolism in Arctic charr. Heat output increased almost linearly from 3.4 to 16.7 microW ind(-1) (0.09-0.67 microW mg(-1)) during the embryonic development. Although the metabolic rate varied between the families and egg metabolic rate increased during development, there was an unexpected disconnect between metabolic rate and hatching time.

A key question of evolutionary importance is what factors influence who becomes dominant. Individual genetic variation has been found to be associated with several fitness traits, including behaviour. Could it also be a factor influencing social dominance? We investigated the association between social status and the amount of intra-individual genetic variation in juvenile brown trout (Salmo trutta). Genetic variation was estimated using 12 microsatellite loci. Dominant individuals had higher mean heterozygosity than subordinates in populations with the longest hatchery background. Heterozygosity–heterozygosity correlations did not find any evidence of inbreeding; however, single-locus analysis revealed four loci that each individually differed significantly between dominant and subordinate fish, thus giving more support to local than general effect as the mechanism behind the observed association between genetic diversity and a fitness-associated trait. We did not find any significant relation between mean d 2 and social status, or internal relatedness and social status. Our results suggest that individual genetic variation can influence dominance relations, but manifestation of this phenomenon may depend on the genetic background of the population.

Semi-automated fluorescent genotyping of eight polymorphic microsatellite loci was used to assess the level of genetic diversity and population differentiation in Nordic stocks of non-anadromous Arctic charr, Salvelinus alpinus, of both wild and hatchery origin. Highly significant genetic heterogeneity was detected globally across wild and/or hatchery populations and even between populations from lakes separated by as little as six kilometres. The overall level of genetic differentiation among wild populations (FST= 0.360) was substantially higher than that observed between populations of anadromous Arctic charr in Canada using microsatellite data. Cavalli-Sforza and Edward's chord distance was used to construct a neighbour-joining tree and three population clusters were supported with relatively high bootstrap values which included the populations from north-west, north-east and southern Finland respectively. Use of Paetkau et al's individual assignment test further supported the strong differentiation of most populations as well as their classification into the three predicted geographical areas. No significant difference in average allele number or heterozygosity was observed between populations of wild and hatchery origin. However, the effects of hatchery rearing were revealed by a strong increase in the number of deviations from Hardy-Weinberg equilibrium as well as of linkage disequilibrium events in the hatchery stocks compared to natural populations. The population from Lake Saimaa, in south-east Finland, is completely reliant upon aquaculture assistance for its survival. The broodstocks of this population exhibited particularly low levels of genetic variability. Although the hatchery stocks of this population suffer from increased egg and alevin mortality and disease susceptibility, it remains to be determined if this is due directly to a lack of genetic variation as some abundant unstocked natural populations possessed similarly low levels of microsatellite variability.

By simulating all possible offspring genotypic combinations based on pair-wise matings in three vulnerable or endangered populations of salmonids (two Atlantic salmon Salmo salar and one Arctic charr Salvelinus alpinus), family level estimates of potential offspring genetic diversity were calculated using several commonly used genetic diversity estimators (d 2 EST, d 2 scaled-EST and H EST ). By using this approach. the genetic variability of offspring could be predicted accurately based solely on parental genotype data. In addition, significant associations between offspring genetic variability and fitness-related traits were observed in the two Atlantic salmon populations and these associations were consistent between fitness measures and either estimated or observed genetic diversity. This indicates that associations with offspring fitness measures can be predicted without genetic analysis of the offspring themselves.

Animals with determinate growth have shown little variation in individual growth patterns, but similar analyses for animals with indeterminate growth have been lacking. We analysed the amount of phenotypic variation in growth patterns across ages among individuals of a hatchery-based population of Arctic charr, Salvelinus alpinus, Salmonidae, using the infinite-dimensional model and including the effects of group size structure. There was little phenotypic variation in growth trajectories: individuals that were small (in relation to the mean) early in life were among the smallest 2.5 years later. If the genetic variation reflects phenotypic variation, not much evolutionary change can be expected. Our results show that there are ecological conditions that determine the strong covariation of size across ages, most likely size-related dominance behaviour, which can mask the true variation of growth patterns. Thus, social interactions can have strong evolutionary effects on traits not directly involved in the behavioural interactions.

Ontogenetic niche shifts are ubiquitous in nature. However, in most species little is known about phenotypic plasticity in the timing of shifts and in the associated characters. Following a period of endogenous feeding on yolk, salmonid alevins emerge from their gravel nests into the open water and start feeding exogenously. We studied, by using replicated artificial nests, whether the responses of emerging Atlantic salmon (Salmo salar) alevins to chemical cues from two piscivorous fish predators and conspecific competitors are plastic. We hypothesised that the alevins should delay emergence in response to predator cues, whereas cues from competitors should induce earlier emergence. We found that chemical cues from predatory burbot (Lota lota) delayed emergence, whereas cues from brown trout (S. trutta) tended to induce earlier emergence. The earlier emergence in response to trout cues was associated with a smaller body size and more yolk resources remaining at emergence, but burbot cues did not alter these traits. Predator cues also influenced the daily pattern of emergence: more alevins emerged during the morning in the burbot treatment, and fewer alevins emerged during the afternoon in the trout treatment. Chemical cues from conspecific competitors had no effect on emergence patterns. The results indicate that salmon alevins exhibit flexible ontogenetic niche shifts in the timing of emergence in response to predator cues, and that the responses are predator-specific. As timing of emergence is a major determinant of territory acquisition, these responses are likely to have an impact on later fitness of the fry.

Summary 1. Studies focusing on the physiological variation between populations and its connection to fitness-related traits are rare, even though integrating these fields would increase knowledge on the evolution of traits. Standard metabolic rate (SMR) has been suggested to influence an individual’s social status and the level of aggressiveness, as dominant individuals tend to have higher SMR than subordinate individuals. 2. The SMR of juvenile Brown Trout (Salmo trutta) from four populations was measured, and the population-level relationship between SMR and aggressiveness, which is a fitness-related behavioural trait, was investigated. 3. SMR differed between the populations, but no differences were found in the amount of aggression. Nevertheless, a significant positive correlation between aggressiveness and SMR between the populations was found. 4. Unlike many previous studies on geographical variation of metabolic rate, SMR correlated negatively with the latitude of origin of the populations. 5. The results suggest that SMR and aggressiveness are correlated not only at the individual level as shown by previous studies, but also at the population level. The costs and benefits of high metabolic rate depend largely on the environment, and local differences in environmental conditions, as for example in food availability, may select for local differences in SMR.

Silvering of the skin, reduced condition factor, elevated gill Na + , K + -ATPase activity and well-developed capacity to regulate the osmotic and ionic balance in sea water were observed in I and 2 year old hatchery-reared Saimaa landlocked salmon Salmo salar m. sebago during April--June. Loss of hypoosmoregulatory ability and gill Na + ,K + -ATPase activity was observed earlier in 2 year than 1 year old fish. Coincident with changes associated with smolting both age groups showed diminished osmoregulatory capacity in fresh water. Slow growth during May-June may also be attributed to osmoregulatory difficulties in fresh water. These results support the suggestion that the developmental changes at smolting are seasonal and unrelated to any salinity changes and the idea of smolting as evidence of maladaptation of the fish to fresh water.

Aggressiveness of juvenile salmonid populations has been suggested to correlate positively with the time the fish spend in the stream. Consequently, resident populations are expected to be more aggressive than migratory populations. Aggressiveness and growth rate have been found to correlate positively at the individual level, but no studies have compared populations. We studied variation in aggressiveness and growth in 10 Finnish brown trout populations differing in their migratory behaviour (sea-run, lake-run and resident). Contrary to expectations, we found the sea-run populations to be more aggressive than the lake-run and resident populations. As all the study fish were reared under similar conditions, it is likely that the differences in aggression have a genetic basis. We also found a positive correlation between aggression and growth rate among the populations. This result supports earlier findings of a positive connection between aggressiveness and growth rate, but is, to our knowledge, the first time this phenomenon has been observed at the population level.

Familiarity is an important factor reducing aggressiveness among individuals. Because of the reduced energy and time expenditure due to lowered aggression, individuals would be expected to perform better in groups of familiar conspecifics as compared with individuals in groups of strangers. However, few studies have examined potential fitness consequences of familiarity. We created familiar (from tanks where several thousands of unrelated fish had been kept since fertilization) and unfamiliar (by combining fish from several tanks) groups of underyearling Arctic char (Salvelinus alpinus) and followed their performance for a 21-day period. Familiarity within groups enhanced survival and body condition of the fish. The fish in familiar groups also grew better in weight and in length. Furthermore, fa - miliar fish differed less in length variation after the experimental period compared with fish reared in unfamiliar groups. There was also a tendency towards similar difference in the variation of weight. These results provide direct evidence for beneficial fitness consequences of early familiarity in Arctic char. Resume : La familiarite est un facteur important de reduction de l'agressivite entre les individus. A cause de la dimi - nution des depenses d'energie et de temps due au declin de l'agressivite, les individus devraient fonctionner mieux parmi des groupes conspecifiques familiers que parmi des groupes d'etrangers. Peu d'etudes ont cependant examine les consequences potentielles de la familiarite sur le fitness. Nous avons cree des groupes d'Ombles chevaliers ( Salvelinus alpinus) de moins de 1 an, familiers (en gardant depuis leur fecondation des milliers de poissons non apparentes dans des aquariums) et non familiers (en melangeant des poissons de plusieurs aquariums) et nous avons suivi leur perfor- mance pendant 21 jours. La familiarite a l'interieur du groupe augmentait la survie et la condition des poissons; la croissance en masse et en taille etait amelioree. De plus, a la fin de l'experience, les poissons familiers affichaient moins de variation dans leurs tailles que les poissons non familiers; les variations de masses suivaient la meme ten- dance. Il s'agit donc d'une preuve directe des consequences benefiques sur le fitness d'une familiarite a un âge precoce chez les Ombles chevaliers. (Traduit par la Redaction) Seppa et al. 1385

The trout (Salmo trutta) has been divided into three forms: sea-run trout, lake-run brown trout, and resident brown trout. They differ in their living environment, migratory behaviour, growth and appearance. As local trout populations are often isolated, and gene flow between them is minimal, differentiation between populations can be expected. The morphology of 1-year-old trout from ten populations representing all three forms was studied in a common-garden experiment. The fish were reared under similar environmental conditions, and 20 morphometric characters were measured from each individual fish. Marked morphological differentiation was found, and differences between populations were greater than differences between forms. The results suggest that the differences have a genetic basis, and they are likely to indicate adaptation to local environmental conditions in the native habitat of the trout.

In order to provide guidelines for conservationand management of the severely declining LakeSaimaa (eastern Finland) European grayling(Thymallus thymallus, Salmonidae), weinvestigated the microgeographic geneticstructure of three populations from the watersystem using 17 microsatellite loci andmitochondrial DNA polymerase chainreaction-restriction fragment lengthpolymorphism analysis. Microsatellites revealedlow levels of intrapopulation genetic diversityand substantial divergence between populationssampled from spawning sites separated by aslittle as 55 kilometers. Mitochondrial analysisindicated the occurrence of two compositehaplotypes within Lake Saimaa. The nucleotidesubstitution estimates between the haplotypessuggested their separation to markedly predatethe late Pleistocene period. The populationsexhibited marked frequency differences for thetwo mitochondrial haplotypes, reinforcing theview of limited interpopulation gene flowwithin Lake Saimaa. An individual basedmicrosatellite Neighbor-Joining dendrogramdemonstrated clustering of all the specimensaccording to their sampling origin. Individualassignment tests revealed 100% assignmentsuccess of individuals into their population oforigin and 100% exclusion (p

Phenotypic plasticity in morphology is often considered adaptive. Stream-living fish encounter considerable spatial and temporal environmental variation in their native habitats, and the ability to ...

In stark contrast to other species within the Salmonidae family, phylogeographic information on European grayling, Thymallus thymallus, is virtually nonexistent. In this paper, we utilized mitochondrial DNA polymerase chain reaction-restriction fragment length polymorphism (mtDNA PCR-RFLP) and sequence variation to infer the postglacial dispersal routes of T. thymallus into and within northern Europe, and to locate geographically, potential evolutionarily distinct populations. Mitochondrial analyses revealed a total of 27 T. thymallus haplotypes which clustered into three distinct lineages. Average pairwise interlineage divergence was four and nine times higher than average intralineage divergence for RFLP and sequence data, respectively. Two European grayling individuals from the easternmost sample in Russia exhibited haplotypes more genetically diverged from any T. thymallus haplotype than T. arcticus haplotype, and suggested that hybridization/introgression zone of these two sister species may extend much further west than previously thought. Geographic division of the lineages was generally very clear with northern Europe comprising of two genetically differentiated areas: (i) Finland, Estonia and north-western Russia; and (ii) central Germany, Poland and western Fennoscandia. Average interpopulation divergence in North European T. thymallus was 10 times higher than that observed in a recent mtDNA study of North American T. arcticus. We conclude that (i) North European T. thymallus populations have survived dramatic Pleistocene temperature oscillations and originate from ancient eastern and central European refugia; (ii) genetic divergence of population groups within northern Europe is substantial and geographically distinct; and (iii) the remainder of Europe harbours additional differentiated assemblages that likely descend from a Danubian refugium. These findings should provide useful information for developing appropriate conservation strategies for European grayling and exemplify a case with a clear need for multinational co-operation for managing and conserving biodiversity.

The ability to distinguish among chemical cues from multiple predators is of key adaptive value for many prey fish. We examined the attractiveness and repulsiveness of chemical stimuli from different coexisting fish species fed on different diets on the behaviour of hatchery reared Arctic charr young in a Y-maze fluviarum, where the charr could choose between two sides either with control water or stimulus water with fish odour. We used stimuli from (1) matching sized conspecifics, large (2) Arctic charr, (3) salmon, (4) brown trout and (5) brown trout fed on Arctic charr fry. Other salmonids were given pellet food. Additional fish odour treatments included piscivorous (6) pike and (7) burbot. In the control trials both sides received control water. Arctic charr young were expected to respond adaptively to the stimuli from coexisting piscivorous fish. The charr most strongly preferred water with the odour of their matching sized conspecifics, which was the only fish odour they were familiar with before the experiments. They also showed significant preference for other salmonid odours, even though these fish are potential predators on small charr. Chemical stimuli from pike and burbot, on the contrary, were strongly avoided, and burbot odour even prevented the charr to swim and enter the lateral halves of the fluviarum. Moreover, odour from brown trout fed on Arctic charr fry was avoided when compared to stimuli from trout fed on pellets. Although the Arctic charr young were completely naive regarding piscivores, the fact that they could distinguish between different predator taxa and diets on the basis of chemical cues only reflects the long coevolutionary history of these fish populations.

We studied whether social environment in the form of different body size regimes in rearing groups affects the growth of juvenile Arctic char (Salvelinus alpinus) in hatchery conditions. Young-of-the-year Arctic char were divided into groups of three different compositions (a wide, a bimodal, and a narrow size-frequency distribution) in which individuals would be subjected to different dominance and competitive relationships. After a 9-month growth period the fish in the narrow size distribution had grown the fastest in both length and weight. Also, total biomass gains were highest for fish originating from the narrow size distribution treatment. The adjusted mean biomasses for wide, bimodal, and narrow size regime treatments were 5400, 5000, and 5900 g, respectively. Our results give support to the hypothesis that individuals in size-sorted groups should show enhanced growth compared with individuals originating from a wider size-frequency distribution where more aggressive interactions are to be expected.

Genetic variation and inheritance of random amplified polymorphic DNA (RAPD) markers were studied in 20 intra- and interspecific crosses between nonanadromous salmon (Salmo salar) and brown trout (S. trutta). Altogether 21 parent fish and 166 F1 individuals were studied. Three of the 40 primers tested produced screenable and reproducible DNA markers which separated nonanadromous salmon and brown trout. The inheritance of RAPD markers was strictly Mendelian and dominant in all types of crosses. Nonparental bands were not generated from DNAs of F1 individuals and it is suggested that the frequency of nonparental bands should be less than 0.03% of all bands. The amount of genetic variation was generally low since nonanadromous salmon were totally monomorphic and in brown trout three primers produced six polymorphic DNA fragments. Mean similarity ( s ) among 11 unrelated specimens of brown trout was 0.941 and between species ( s ) was 0.338. Among parents, 11 out of 27 and 14 out of 24 DNA fragments were unique for nonanadromous salmon and brown trout, respectively. It is concluded that the RAPD method is one of the most time-saving and the least expensive noninvasive method for detection of interspecific hybridization.

Cryopreservation of brown trout (Salmo trutta m. lacustris) and Arctic charr (Salvelinus alpinus) sperm was studied by modifying sperm extenders and the amount of egg yolk (10 or 20%) as a protective component. Glycerol and dimethylsulphoxide (5–25%) in a 0.3 M glucose solution were compared as cryoprotectants for Arctic charr sperm. Milt pellets (ca. 0.05 ml) frozen on dry ice (−79°C) were stored in liquid nitrogen (−196°C). Fertilization rates with cryopreserved sperm ranged from 31 to 85% of the controls (fresh sperm) for brown trout and from 25 to 75% for Arctic charr. The storage time did not change these values, and only a minor part of the variation was caused by the type of extender. In brown trout, the fertilization procedure had a pronounced effect on post-thaw fertility. The highest fertilization rate was achieved when the eggs were inseminated using the fertilization diluent of Billard (1977) and water was added 5–6 min after the sperm. Addition of egg yolk to the extenders increased the fertilization rates in brown trout. For protection of Arctic charr sperm, glycerol proved to be better than DMSO. The crycprotective potential of both agents was dependent on the concentration. The highest fertilization rate was obtained by combining the optimal glycerol level (20%) with either 0.3 M glucose or Mounib's (1978) media.

The parental influences on three progeny traits (survival to eyed-embryo stage, post-hatching body length and yolk-sac volume) of Arctic charr Salvelinus alpinus were studied under two thermal conditions (2 and 7 degrees C) using a factorial mating design. The higher temperature resulted in elevated mortality rates and less advanced development at hatching. Survival was mostly attributable to maternal effects at both temperatures, but the variation among families was dependent on egg size only at the low temperature. No additive genetic variation (or pure sire effect) could be observed, whereas the non-additive genetic effects (parental combination) contributed to offspring viability at 2 degrees C. In contrast, any observable genetic variance in survival was lost at 7 degrees C, most likely due to the increased environmental variance. Irrespective of temperature, dam and sire-dam interaction contributed significantly to the phenotypic variation in both larval length and yolk size. A significant proportion of the variation in larval length was also due to the sire effect at 2 degrees C. Maternal effects were mediated partly through egg size, but as a whole, they decreased in importance at the high temperature, enabling a concomitant increase in non-additive genetic effects. For larval length, however, the additive component, like maternal effects, decreased at 7 degrees C. The present results suggest that an exposure to thermal stress during incubation can modify the genetic architecture of early developmental traits in S. alpinus and presumably constrain their short-term adaptive potential and evolvability by increasing the amount of environmentally induced variation.

Temporal consistency of relative standard metabolic rate (rSMR) of individual Atlantic salmon Salmo salar juveniles in three stocks was investigated. The stocks differed in their geographical origin and natal habitat (fresh water, brackish water, seawater). Oxygen consumption measurements of hatchery-reared fish hatched in February 2005 were conducted three times: in early spring 2006, in autumn 2006, and in late spring 2007. The results partly disagreed and partly agreed with earlier studies, in which temporal consistency of SMR in juvenile salmonids have been addressed. In the first period from early spring to autumn, no correlation between rSMR statuses of individuals was found whereas in the second period from autumn to late spring, fish were mainly observed to maintain their relative SMR level indicating a significant repeatability of individual rSMR status over the latter period. Furthermore, a relationship between rSMR status and life history strategy was found: post-smolts and smolts had higher SMR than non-smolts.

Assignment of an individual to the population from which it most probably originated based on its multilocus genotype has been widely applied in recent years. In this study, individual assignment based on microsatellite data was used to identify a case of fishing competition fraud. Despite the fact that the true population of origin was most probably not among the reference populations, recent modifications of the assignment tests were used in confidently excluding (p < 0.0001) the possibility of a 5.5 kg salmon (Salmo salar) originating from the fishing competition location, Lake Saimaa (south-east Finland). In fact, the probability of the suspect salmon originating from one of the regions that supply most of Finland's fish markets was found to be over 600 times higher than it originating from Lake Saimaa. When presented with this evidence, the offender confessed to purchasing the salmon at a local fish shop and criminal charges were laid. This study emphasizes the potential practical application of the individual assignment procedure, in particular the usefulness of confidently excluding populations as the origin of an individual. A similar strategy could be also used, for example in suspected cases of illegal poaching, in order to assign or exclude individuals from originating from a claimed population.