Search

The ecology of salmonids is tightly linked to their spawning habitats, but the link between spawning site selection and phenology is poorly understood. To address this, we studied the Arctic charr (Salvelinus alpinus) from the postglacial lake Thingvallavatn (Iceland) through a multidisciplinary approach involving aerial surveys, behavioural observations, temperature monitoring and embryo rearing experiments. Aerial footage revealed that most nests (i.e. redds) were established in shallow parts of the spawning area, and we reported through direct observations trends for stronger male–male competition and for more frequent courtship behaviours in shallow than in deep redds. While water depth did not correlate with temperature at the time of spawning, the temperatures recorded at the shallow redds were consistently lower in the two months following the video recordings, likely because of the proximity of glacial outlets. Laboratory experiments demonstrated that the temperature regimes in shallow waters can delay hatching with about a month, likely impacting the phenology of the offspring. The viability of the Arctic charr in Thingvallavatn may thus depend on physical features like groundwater springs and upwelling water flows acting as "temperature shelters". [ABSTRACT FROM AUTHOR]

Individual measurements of annual, or within-season growth were determined from tag-recaptured Arctic charr and examined in relation to summer sea surface temperatures and within-season capture timing in the Ungava and Labrador regions of Eastern Canada. Differences between two years of growth (2010-2011) were significant for Ungava Bay Arctic charr, with growth being higher in the warmer year. Growth of Labrador Arctic charr did not vary significantly among years (1982-1985). Regional comparisons demonstrated that Ungava Arctic charr had significantly higher annual growth rates and experienced warmer temperatures than Labrador Arctic charr. The higher annual growth of Ungava Bay Arctic charr was attributed to the high sea surface temperatures experienced in 2010-2011 and the localised differences in nearshore productivity as compared to Labrador. Within-season growth rates of Labrador Arctic charr peaked in June, declined towards August and were negatively correlated with the length of time spent at sea and mean experienced sea surface temperatures. A quadratic model relating growth rate to temperature best explained the pattern of within-season growth. Collectively, results suggest that increases in water temperature may have profound consequences for Arctic charr growth in the Canadian sub- Arctic, depending on the responses of local marine productivity to those same temperature increases. [ABSTRACT FROM AUTHOR]

Spawning is a key but often fragile event in the life cycles of fish populations. Nevertheless, it has been relatively little studied for lithophilic lacustrine species requiring hard spawning substrates, such as gravels or stones, largely devoid of fine sediments. Twelve demonstrated or putative spawning grounds of Arctic charr ( Salvelinus alpinus) in shallow and deep areas of the north and south basins of the eutrophicated lake of Windermere, UK, were described by hydroacoustic, physical and visual surveys. In addition, their current conditions were compared with their original qualitative descriptions made over 50 years ago. Spawning ground characteristics were found to be more complex than originally described, with considerable overlaps in depth ranges and only limited areas of appropriate hard substrates. Moreover, extensive gill netting surveys in recent years have found spawning Arctic charr at only seven of the original 12 demonstrated or putative spawning grounds, although several new spawning areas have also been found. The distribution of unsuitable fine sediments is widespread in the lake, particularly in the more eutrophicated south basin where suitable spawning habitat within the putative spawning areas is limited. Windermere faces a number of environmental problems including climate change and species introductions. However, the temporal and spatial patterns of the lake's eutrophication suggest that associated increases in fine sediments have been a major driver of the observed deterioration of Arctic charr spawning grounds and so may have also contributed to a marked decline recently observed in the local abundance of this species. [ABSTRACT FROM AUTHOR]

Two modal size groups of sexually mature Arctic charr ( Salvelinus alpinus) differing in shape and found at different depths in Lake Aigneau in the Canadian sub-Arctic are described and tested for genetic and ecological differentiation. Forms consisted of a small littoral resident, mean size 21.7 cm, and a large profundal resident, mean size 53.9 cm. Mitochondrial DNA analysis indicated that seven of eight haplotypes were diagnostic for either the littoral or profundal fish, with 66.6% of the variation being found within form groupings. Pairwise tests of microsatellite data indicated significant differences in nine of 12 loci and a significant difference between the forms across all tested loci. Molecular variation was partitioned to 84.1% within and 15.9% between forms and suggestive of either restricted interbreeding over time or different allopatric origins. Stable isotope signatures were also significantly different, with the profundal fish having higher δ13C and δ15N values than the littoral fish. Overlap and separation, respectively, in the range of form δ13C and δ15N signatures indicated that carbon was obtained from similar sources, but that forms fed at different trophic levels. Littoral fish relied on aquatic insects, predominantly chironomids. Profundal fish were largely piscivorous, including cannibalism. Predominantly empty stomachs and low per cent nitrogen muscle-tissue composition among profundal fish further indicated that the feeding activity was limited to the winter when ice-cover increases the density of available prey at depth. Results provide evidence of significant differences between the modal groups, with origins in both genetics and ecology. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We investigated how Arctic charr young respond behaviourally to olfactory cues from skin-damaged conspecifics, charr-fed pikeperch, and the combination of food-deprived pikeperch and skin-damaged conspecific cues in a two-channel Y-maze fluviarium test arena. Significant antipredator responses were found to skin-damaged conspecifics in three behavioural traits, to charr-fed pikeperch in two traits and to the combination of pikeperch and skin-damaged conspecific cues in all six behaviours investigated. The combination of predator and conspecific cues significantly increased spatial avoidance and cautiousness to approach the source of scent compared with odours from charr-fed predators. The results suggest that damage-released alarm cues exist in charr, and they strengthen the antipredator responses in conspecifics. As the charr used different behaviours and levels of response in the presence of different cues, they seem to have sophisticated skills to distinguish between different odour combinations and be able to adjust their behaviour according to the current predation risk level. [ABSTRACT FROM AUTHOR]

The Arctic charr Salvelinus alpinus (L.), or Torgoch (‘red belly’) in Welsh, is found in seven lakes in North Wales comprising three native populations (Bodlyn, Cwellyn and Padarn) and four translocated populations (Cowlyd, Diwaunedd, Dulyn and Ffynnon Llugwy). The Welsh charr populations have not been studied much, but the available data are summarised in this short review. Analysis of stomach contents of the native charr populations shows that they are planktivores feeding mainly on cladocerans and copepods. Adult fish attain a size of 14–24 cm (fork length) and fecundity is low (100–800 eggs per female). The available growth data reveal that Welsh charr grow at a similar rate and attain a size similar to most other planktivorous charr populations that have been studied in the UK. Genetic studies using allozymes indicate that the three native populations are distinct from each other. [ABSTRACT FROM AUTHOR]

In this study, we synthesised the views of 34 participants in a workshop to consider the status and future conservation and management of the Arctic charr ( Salvelinus alpinus L.). These are expressed as a series of resolutions deriving from a conference on Arctic charr conservation held in Perth, Scotland in June 2004. Agreed resolutions from the conference were as follows. (i) The unique diversity of Arctic charr should be recognised for the contribution it makes to biodiversity of northern aquatic communities. (ii) The recognition by the public, nongovernmental organisations and national governments of the importance of Arctic charr in northern ecosystems is an important step to the management and protection that should be pursued. (iii) The taxonomic status of highly variable charr populations requires to be reviewed. (iv) There should be a separate system, complementary to the taxonomic one, which systematically catalogues the biological diversity of S. alpinus. (v) The Arctic charr provides a unique natural resource to study the process of evolution and this requires the highest level of protection from anthropogenic effects. (vi) The status of conservation policy for Arctic charr needs to be urgently reviewed to take account of its unique position in the fauna. [ABSTRACT FROM AUTHOR]

Hydroacoustic surveys are an important tool for assessing the abundance of Arctic charr ( Salvelinus alpinus (L.)) in lakes, the requirement for which is increasing because of new environmental legislation. Consequently, survey demand is now such that assessments must be undertaken with the minimum of effort compatible with scientific validity. One major complication is seasonal variability in abundance, with which surveyors have attempted to deal by defining somewhat arbitrary seasonal sampling windows. The definition of more objective windows was pursued by analysing variations in the seasonal abundance of Arctic charr in Windermere, UK, recorded using day and night hydroacoustic surveys at monthly intervals from 1991 to 2001. Two alternative sampling windows for night surveys free of significant internal seasonal effects were revealed, i.e., December to September and September to December. It was also found that day surveys gave a useful, although lower, estimate of abundance as compared with night surveys. [ABSTRACT FROM AUTHOR]

From both a modern and a historical perspective there is little doubt that the Arctic charr, Salvelinus alpinus, in Britain and Ireland (as well as elsewhere) is a ‘difficult’ species. Historically 15 separate species have been recognised from populations in Britain and Ireland and there have been recent attempts to reassert these specific names. Here we review the evidence for the status of these ‘species’. We conclude that the evidence for these 15 being afforded full species status is poor. However, both historical and contemporary data show that Salvelinus alpinus (Linnaeus 1758) in Britain and Ireland exhibits levels of variability in form that is much greater than in other species. We argue that a comprehensive genotypic and phenotypic survey of charr populations in Britain and Ireland is required to determine the full extent of variability and the status of populations with a view of providing suitable protection. [ABSTRACT FROM AUTHOR]

Arctic charr, Salvelinus alpinus (L.), is one of the several northern fishes that show resource polymorphisms in postglacial lakes. Two reproductively isolated morphs of Arctic charr coexist in distinct ecological niches in the subarctic lake Fjellfrøsvatn, North Norway. Offspring of the two morphs (termed littoral charr and profundal charr) were reared separately but under identical conditions. Their feeding behaviour was compared experimentally using different kinds of live prey. The fishes had no experience with natural prey before the experiments. The littoral morph were more effective in eating live plankton ( Daphnia) and littoral benthos ( Gammarus), and had a higher attack rate against pleuston (surface prey, Gerris) compared with the profundal morph. The two morphs behaved in accordance with expectations from their in situ niche utilisation towards the three prey types. This indicates a case of incipient ecological speciation where divergence in resource utilisation in contrasting niches has evolved adaptations in feeding behaviour by natural selection. [ABSTRACT FROM AUTHOR]