Reproductive strategies of Arctic charr Salvelinus alpinus (L.) forms in Kiryalta lakes,Transbaikalia, Russia

Lake Abaya and Lake Chamo are the two largest Ethiopian Rift Valley lakes; they are located close to each other, but have a strikingly different water transparency. We explain key differences in the structure and the functioning of the food web with variation in limnological variables and major pelagic food web compartments within and across both lakes. Data from a detailed comparative investigation of physical and chemical variables and zooplankton community characteristics during the wet and dry season from two consecutive years revealed major differences in key limnological variables between Lake Abaya and Lake Chamo. The most pronounced differences were related to water transparency and the amount of suspended solids in the water column. Lake Abaya is much more turbid, has lower phyto- and zooplankton biomass, and has considerably lower primary production than Lake Chamo. Based on our results, we infer that the profound differences in food web structure between both lakes probably result from differences in sediment load. Finally, our results indicate that conservation programs should focus on reducing sediment inflow from the catchments into the lakes.

     

Three sympatric forms of Arctic charr Salvelinus alpinus complex (Salmoniformes,Salmonidae) from Lake Kamkanda,Northern Transbaikalia

We studied morphology, size and age structure, growth, feeding, and variation at microsatellite loci of three forms of Arctic charr Salvelinus alpinus complex (dwarf, small, large) from mountain Lake Kamkanda in River Olekma basin, northern Transbaikalia. The forms differ in meristic and morphometric characters, external appearance and size. The small form distinctly differs from the dwarf and large forms in higher number and length of gill rakers. The forms differ in growth rate; however, differences in growth between the dwarf and the small forms are not as large as between sympatric dwarf and small charr from other Transbaikalian lakes. The large form is heterogeneous in growth rate. The small form matures one year earlier than the dwarf form and has a shorter life span. The dwarf form is a benthophage, the small form is a planktophage, and the large form is a predator. The dwarf form spawns in September, while the small form spawns in November-December, and there is no overlap in their spawning time. The three forms have clear genetic differences, which support their reproductive isolation. It is assumed that the three forms of Arctic charr originated within Lake Kamkanda on the basis of trophic polymorphism and spawning time displacement and attained a high degree of morphological and genetic divergence.     

Polymorphic segregation in Arctic charr Salvelinus alpinus (L.) from Vatnshlidarvatn, a shallow Icelandic lake

We studied the salmonid fish Arctic charr, Salvelinus alpinus , in a small and shallow landlocked lake in NW Iceland. The lake is productive but die only fish present is Arctic charr. Despite the apparent absence of discrete benthic and limnetic habitats for fish, two forms of Arctic charr are found in the lake. They show subde differences in morphology related to swimming performance and manoeuvrability, but differences in life history such as growth, and age and size at sexual maturation are more pronounced. Both forms have benthic feeding habits with one form consuming greater number of species than the other. We suggest that the segregation of these forms is based on the evolution of a specialist from a local generalist and that this has been made possible by the absence of a common fish competitor in similar lakes, the threespined stickleback Gasterosteous aculeatus.     

Sibling recognition in juvenile Arctic charr, Salvelinus alpinus (L.)

Juvenile Arctic charr, Salvelinus alpinus (L.), from two full sibling groups were studied concerning the possible existence of chemical cues with information about kinship. Each full sibling group was divided into two groups with the same number of specimens and placed in two separate aquaria. The division coincided with the start of exogenous feeding. Preference tests were performed about 7 and 10–13 months after the division. Due to the increasing size of experimental fish, two different sizes of apparatus were used. The first series of experiments was performed in a small Y-maze fluviarium and the second series in the large standard fluviarium. The momentary positions of one fish at a time in the test area were recorded by time-lapse photography with a 16-mm film camera and filtered flashlight (no transmittance <670 nm). The fish were given a choice between two water qualities; thus the following comparisons were made: (i) unconditioned water ν. water scented by siblings from the same aquarium; (ii) unconditioned water ν. unfamiliar non-siblings; (iii) siblings from the same aquarium ν. unfamiliar non-siblings; (iv) siblings from a separate aquarium ν. unfamiliar non-siblings; (v) siblings from the same aquarium ν. siblings from a separate aquarium. The test fishes preferred water scented by siblings over non-siblings, even though the siblings were taken from a separate aquarium. Nevertheless, they were attracted to water scented by unfamiliar non-siblings in preference to unconditioned water. No preference was shown between chemical cues from siblings taken from the same and a separate aquarium.     

Lake enrichment and the status of Windermere charr, Salvelinus alpinus (L.)

All English populations of Arctic charr, Salvelinus alpinus (L.), are found in the Lake District (northwest England). There are at least four races of charr in Windermere, the largest lake in England; the North and South basins of the lake each contain two distinct races that spawn in autumn and spring respectively. The spring spawners in both basins probably represent less than 15% of the total population in the lake.
Changes in the population density of charr in the lake are described briefly and examined in relation to the trophic status of the lake. Other factors that could possibly affect the charr population are reviewed, especially the influence of climate change.     

Reproduction,condition and food of adult arctic charr (Salvelinus alpinus,L.) in Lake Pavin (Massif Central,France)

RésuméTo determine the role and the importance of adult fish predation directly and indirectly in the food web of oligomesotrophic Lake Pavin, reproduction, condition, and feeding activity of the dominant adult chctic charr (Salvelinus alpinus, L.) were studied. Fish were caught by gillnets of different mesh sizes once a month from April to December 1992. The gonad cycle showed that the spawning period occurred between October to December. Relative fecundity is about 2509 ovules per kg of female fish and ovule mean diameter is 4.7 mm ( 0.6 mm). Seasonal variations of the sex-ratio (Max. in April = 2.67 and Min. in October=0.19) indicated the intralake migrations of females and males. The condition coefficients showed higher values for females than males; the maximum was observed in summer for both sexes and the minimum in April and in October for males and females, respectively. Low values of the condition were also observed during the spawning period. High feeding activity was recorded in spring and in December after reproduction; low feeding activity was observed in October during reproduction. Asellus aquaticus was quantitatively the dominant prey from April to September; during the sp awning period, S. alpinus consumed its own eggs, particularly in large quantity in December. Daphnia longispina was numerically the dominant prey all over the studied cycle and the electivity (Ivlev Index) of arctic charr on the latter prey ranged from +s+0.79 to +0.16. During April, more than 15 500 individuals of D. longispina per kg of fish were found in the gut contents. The selective predation of S. alpinus on benthic (A. aquatics) and zooplankton prey (D. longispina) indicated that the fish immigrate during their feeding activity from benthic/littoral to the pelagic area.Afin de d terminer le rôle et l'importance de la prédation directe et indirecte de l'omble chevalier adulte (Salvelinus alpinus, L.) dans le réseau trophique du lac Pavin, milieu oligo- mésotrophe, nous avons étudié la reproduction, deux facteurs de condition et l'activité alimentaire de ce poisson qui est l'espéce dominante dans ce lac. Les poissons ont été capturés par des filets maillants de différent vide de maille selon un pas d'échantillonnage mensuel d'avril á décembre 1992. Le cycle du développement des gonades montre que la période de reproduction se déroule entre octobre et décembre. La fécondité relative calculée est de 2509 ovules par kg de femelles et le diamétre moyen d'un ovule est de 4,7 mm ( 0,6). Les variations saisonniéres du sex-ratio (Max. en avril = 2,67 et Min. en octobre=0,19) indiquent le déplacement actif et successif des femelles et des mâles. Les variations saisonniéres des coefficients de condition indiquent une copulence plus importante des femelles par rapport aux mâles avec des valeurs maximales en été pour les deux sexes et des valeurs minimales en avril et en octobre pour les mâles et les femelles respectivement. De faibles valeurs des facteurs de condition ont été observées pendant la période de reproduction pour les deux sexes. L'activité alimentaire de l'omble chevalier est intense au printemps et au mois de décembre aprés la fraie et faible au mois d'octobre pendant la reproduction. Asellus aquaticus est, en termes de biomasse, la proie dominante d'avril á septembre. Pendant la période de reproduction, S. alpinus se nourrit de ses propres oeufs sur les zones de frayéres et en décembre la quantité d'oeufs consommée par le Salmonidé est importante. Daphnia longispina est, en termes d'abondance, la proie dominante tout au long de cette étude et l'indice d'électivité (Indice d'Ivlev) de l' ombre chevalier vis-á-vis de cette proie varie entre + 0,79 et + 0,16.De plus, au mois d'avril, plus de 15 500 D. longispina par kg de poisson ont été enregistrées dans les contenus stomacaux. La prédation sélective de S. alpinus sur des proies benthiques (A. aquaticus) et zooplanctoniques (D. longispina) indique que le poisson effectue des déplacements en fonction de son activité alimentaire de la zone littorale/benthique á la zone pélagique.     

Status of arctic charr (Salvelinus alpinus) farming in Norway, Sweden and Iceland

This article describes the status of the Arctic charr (Salvelinus alpinus L.) aquaculture industry in Iceland, Norway and Sweden. The purpose of the work was to give an update on the status of Arctic charr farming in these countries based on information obtained from the industry itself. The data were collected using questionnaires designed for the purpose with key personnel in each country interviewing the farmers or farm managers. The questions were divided on topics focusing on different sides of the production, including farm characteristics, biological challenges and markets. The aim was to identify strengths and weaknesses in the production related to country and production technologies. The information may prove useful for decisions and prioritising future research and development work on removing bottlenecks and improving sustainable production of Arctic charr.     

Smolting characters in anadromous and resident Arctic charr, Salvelinus alpinus (L.)

Morphological differences, haematocrit value and chloride cells were examined in downstream migrating Arctic charr, Salvelinus alpinus (L.) from the Hals River, North Norway, and resident charr from Lake Storvann. Fish were classified as visual parr, silvery parr or smolt based on the degree of silvering and the Occurrence of lateral parr marks. On average, 47% of downstream migrating Arctic charr were classified as visual molts, but only 14% of the resident charr. Charr longer than 20 cm fork length were mainly classified as visual molts. Morphometrical analyses of body size and shape revealed that most of the variations could be explained in terms of variations in fork length. Length adjusted ratios of post-anal distances were significantly higher in migrating charr than in resident charr. The number of developed chloride cells, the cell nucleus diameter in the basin of secondary gill lamellae and blood haematocrit values were significantly higher among downstream migrating charr than in resident charr. However, morphological differences between anadromous and resident Arctic charr were not necessarily synchronized with the development of chloride cells.     

Quantitative protein requirements of Arctic charr, Salvelinus alpinus (L)

Arctic charr, Salvelinus alpinus , require diets with protein energy (PE): total energy (TE) ratios of at least 0.35 in order to maintain good rates of growth. The protein requirement is, therefore, similar to that of rainbow trout, Salmo gairdneri . Protein retention efficiency (PPV) declined as the protein content of the diet was increased, the relationship being described by the equation: It is suggested that charr will maintain good rates of growth if fed on diets used for commercial culture of rainbow trout and special formulations for charr should not be necessary.     

Chromosomes and constitutive heterochromatin distribution in Arctic charr,Salvelinus alpinus (L.) (Pisces: Salmonidae)

The chromosomes, together with their C and Q banding patterns, of Arctic charr from Loch Rannoch, Scotland are described. Q banding revealed fewer bands than C banding and variation between individuals for the number of C bands was found. These results suggest that subsets of heterochromatin exist and that there may be an individual variation in DNA content.     

Spawning coloration and sperm quality in a large lake population of Arctic charr (Salmonidae: Salvelinus alpinus L.)

The modern theories of sexual selection predict that male sexual ornaments may have evolved as reliable signals of male fertilization efficiency. However, among the studies of fishes with external fertilization, the results have yielded ambiguous evidence. In the present study, we present data on the phenotypic relationships between red spawning coloration and ejaculate quality (spermatocrit, sperm motility) from Arctic charr, Salvelinus alpinus. We studied two generations (F₁ and F₂) of males from a large lake population, reared in a standardized hatchery environment, to determine whether differential hatchery history, or duration of hatchery selection, affected the variation in ejaculate characteristics or abdominal coloration. After controlling for body length, there was no difference between the hatchery generations in these traits. However, the degree of redness increased with fish size. We found a positive correlation between sperm velocity and sperm longevity, indicating a functional integration between these sperm features across generations. Sperm velocity was also positively correlated with male redness. Therefore, the finding obtained in the present study suggests that the carotenoid‐based ornamentation in Arctic charr may provide information about differences between males in their fertilization potential. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 794–802.     

The genetics of sympatric Arctic charr [Salvelinus alpinus (L.)] populations from Loch Rannoch, Scotland

Two morphologically and ecologically distinct forms of Arctic charr, Salvelinus alpinus , are found in Loch Rannoch, Scotland. The differences in morphology are adaptations to different modes of life, one being pelagic, the other benthic. Both forms have been the subjects of extensive genetic studies including cytogenetics, nuclear and mitochondrial DNA analysis, and protein electrophoresis. Significant differences between the two forms are revealed by some techniques but not others and provide evidence for the reproductive isolation of these two morphs. The findings are discussed in relation to the derivation of sympatry and the phylogenetics of Arctic charr.     

Parasites of arctic charr Salvelinus alpinus (Linnaeus) and their use in separating sea-run and non-migrating charr

Metazoan parasites of arctic charr, Salvelinus alpinus , from the Nettilling Lake–Koukdjuak River system, Baffin Island, were studied. Non-migrating charr hosted 9 species of parasites while sea-run charr hosted 15 species of parasites. Diphyllobothrium spp., Eubothrium salvelini , and Proteocephalus longicollis were found to be good indicators of non-migrating charr and Brachyphallus crenatus, Bothrimonus sturionis and Prosorhynchus squamatus were good indicators of sea-run charr. Using these parasites as biological tags, the proportion of charr caught by the commercial fishery at the outlet of the Koukdjuak River were determined to be approximately 80% sea-run and 20% non-migrating charr. Step-wise discriminant statistical analysis on morphic characters of charr, designated as sea-run and non-migrating by their parasites, showed these charr to differ morphologically.     

Holarctic phylogeography of Arctic charr (Salvelinus alpinus L.) inferred from mitochondrial DNA sequences

This study evaluated mitochondrial DNA (mtDNA) sequence variation in a 552-bp fragment of the control region of Arctic charr (Salvelinus alpinus) by analyzing 159 individuals from 83 populations throughout the entire range of the complex. A total of 89 (16.1%) nucleotide positions were polymorphic, and these defined 63 haplotypes. Phylogenetic analyses supported the monophyly of the complex and assigned the observed haplotypes to five geographic regions that may be associated with different glacial refugia. Most notably, a formerly defined major evolutionary lineage (S. a. erythrinus) ranging from North America across the Arctic archipelago to the Eurasian continent has now been partitioned into the Arctic group and the newly identified Siberian group. The Beringian group, formed entirely by specimens assigned to S. malma (Dolly Varden), encompassed the area formerly assigned to S. a. taranetzi. The latter, due to a unique haplotype, became the basal member of the Arctic group. Overall, the S. alpinus complex reflects divergent evolutionary groups coupled with shallow intergroup differentiation, also indicated by an analysis of molecular variance that attributed 73.7% (P < 0.001) of the total genetic variance among groups. Time estimates, based on sequence divergence, suggest a separation of the major phylogeographic groups during early to mid-Pleistocene. In contrast, colonization of most of today's range started relatively recently, most likely late Pleistocene during the last retreat of ice sheets some 10,000-20,000 years ago. This time scale obviously is too shallow for detecting significant variation on a smaller scale using mtDNA markers. However, other studies using nuclear microsatellite DNA variation strongly suggested ongoing evolution within groups by revealing strong population-genetic substructuring and restricted gene flow among populations. Thus, Arctic charr could serve as a model organism to investigate the linkage between historical and contemporary components of phylogeographic structuring in fish, and, with a global perspective of the distribution of genetic variation as a framework, meaningful comparisons of charr studies at a smaller geographic scale will now be possible.     

Morphological variation over ontogeny and environments in resource polymorphic arctic charr (Salvelinus alpinus)

SUMMARY Natural selection requires genetically based phenotypic variation to facilitate its action and cause adaptive evolution. It has become increasingly recognized that morphological development can become canalized likely as a result of selection. However, it is largely unknown how selection may influence canalization over ontogeny and differing environments. Changes in environments or colonization of a novel one is expected to result in adaptive divergence from the ancestral population when selection favors a new phenotypic optimum. In turn, a novel environment may also expose variation previously hidden from natural selection. We tested for changes in phenotypic variation over ontogeny and environments among ecomorphs of Arctic charr (Salvelinus alpinus) from two Icelandic lakes. Populations represented varying degrees of ecological specialization, with one lake population possessing highly specialized ecomorphs exhibiting a large degree of phenotypic divergence, whereas the other displayed more subtle divergence with more ecological overlap. Here we show that ecomorphs hypothesized to be the most specialized in each lake possess significant reductions in shape variation over ontogeny regardless of environmental treatment suggesting canalized development. However, environments did change the amount of shape variation expressed in these ecomorphs, with novel environments slowing the rate at which variation was reduced over ontogeny. Thus, environmental conditions may play an important role in determining the type and amount of genetically based phenotypic variation exposed to natural selection.     

The ecological interaction between arctic charr, Salvelinus alpinus (L.), and the plerocercoid stage of Diphyllobothrium ditremum

Six hundred and two arctic charr, Salvelinus alpinus , from a small lake (30 ha) were examined for infection with plerocercoids of Diphyllobothrium ditremum the only species of this genus present; 466 (77.4%) harboured the parasite in an overdispersed infection. The prevalence of infection increased with age and reached 100% at 7+ years for males and 8+ years for females. The rate of infection appeared to be related to the feeding biology of the charr which did not change within the age span studied. The rate of increase in density of infection (plerocercoids per fish) decreased with age as did the degree of overdispersion. It is concluded that the infection probably induces mortality in the fish population, and that such mortality is dependent on parasite density.     

Mitochondrial DNA analysis of Scottish populations of Arctic charr, Salvelinus alpinus (L.)

Mitochondrial DNA analysis of a total of 82 individuals from seven Scottish populations of Arctic charr ( Salvelinus alpinus L.) using restriction fragment length polymorphism and direct nucleotide sequencing of the cytochrome b gene revealed little variation within or between populations. One of 19 restriction enzymes showed a polymorphism that was present in three of the seven populations. Only one nucleotide substitution was detected in a 288 base pair segment of the cytochrome b gene examined in 26 fish. Approximately 4% of the mitochondrial genome was surveyed with these complementary procedures.     

Reproduction and development in the dwarf form of Arctic charr Salvelinus alpinus from Lake Davatchan, Transbaikalia

Biological characteristics in the deepwater dwarf form of Arctic charr Salvelinus alpinus from Lake Davatchan, Transbaikalia, are described. In nine from fifteen attempts of artificial insemination of eggs from a female by sperm from a male, developing eggs are obtained. Embryonic and larval development is described at the initial temperature 1.6–3.6°C and subsequent (from early gastrulation to the transition of larvae to exogenous feeding) average temperature 4.4 and 8.6°C. To take into account the data obtained previously (Pavlov et al., 1990, 1993b), the comparison of early ontogeny is conducted between the dwarf and small forms of charr from Lake Davatchan and the charr from Lake Leprindokan (two lakes are separated by the ridge 8 km in width). A substantial similarity in early ontogeny between the dwarf and small forms of charr from Lake Davatchan suggests that genes controlling development of the embryos and prelarvae until the transition of the young to exogenous feeding have not been subjected to natural selection determining a considerable differentiation between two forms and their reproductive isolation. Published in Voprosy Ikhtiologii, 2008, Vol. 48, No. 1, pp. 102–119. The article was translated by the author.     

The early ontogeny of digestive and metabolic enzyme activities in two commercial strains of arctic charr (Salvelinus alpinus L.)

The extent to which growth performance is linked to digestive or energetic capacities in the early life stages of a salmonid species was investigated. We compared two strains of Arctic charr known to have different growth potentials during their early development (Fraser and Yukon gold). Trypsin, lipase, and amylase activities of whole alevins were measured at regular intervals from hatching through 65 days of development. To assess catabolic ability, we also measured five enzymes representing the following metabolic pathways: amino acid oxidation (amino aspartate transferase), fatty acid oxidation (beta-hydroxy acyl CoA-dehydrogenase), tricarboxylic acid cycle (citrate synthase), glycolysis (pyruvate kinase), and anaerobic glycolysis (lactate dehydrogenase). The measurement of these enzyme activities in individual fish allowed a clear evaluation of digestive capacity in relation to energetic demand. We also compared triploid and diploid individuals within the Yukon gold strain. For the whole experimental period, diploid Yukon gold fish exhibited the highest growth rate (1.08+/-0.18% length/day) followed by triploid Yukon gold fish (1.00+/-0.28% length/day) and finally Fraser strain fish (0.84+/-0.28% length/day). When differences in enzyme activities were observed, the Fraser strain showed higher enzyme activities at a given length than the Yukon gold strain (diploid and triploid). Higher growth performance appears to be linked to lower metabolic capacity. Our results suggest that fish may have to reach an important increase in the ratio of digestive to catabolic enzyme activities or a leveling off of metabolic enzyme activities before the onset of large increases in mass.