Charr Populations Research Articles

Size, age and spawning frequency of landlocked Arctic charr Salvelinus alpinus (L.) in Svartvatnet, Svalbard

This contribution reports the analysis of a sample of landlocked Arctic charr collected with gillnets in Svartvatnet, Svalbard, 1964. This is the first scientific sample from a landlocked charr population from Svalbard. We found a very prominent modal group of large, old and sexually adult fish of both sexes. Their length ranged from 15 to 62 cm, but 92% of the fish were longer than 40 cm and 62% of them fell in the 45 to 54 cm interval. The age range was 7 to 31 years, but 93% were 14 years or older and represented 18 year-classes. The length-at-age of the charr seemed to increase steadily until they reached the size and age of the modal group. The growth rate decreased sharply after that. The mortality rates within the age span of the modal group seemed to be low. The ages at first spawning for most of the charr in the sample were between 7 and 9 years and spawning cycles of two years were indicated.

Evidence for Non-Anadromous Behaviour of Arctic Charr (<i>Salvelinus alpinus</i>) from Lake Hazen, Ellesmere Island, Northwest Territories, Canada, Based on Scanning Proton Microprobe Analysis of Otolith Strontium Distribution

Scanning proton microprobe analysis was used to determine the distribution of strontium (Sr) in otoliths from arctic charr (Salvelinus alpinus) of known non-anadromous, known anadromous, and unknown life histories. Strontium concentration patterns in otoliths of known non-anadromous charr were low and relatively flat (with little variation) from the core area to the outermost edge of the otolith, while patterns for known anadromous charr were characterized by a similar low, flat region for the first several years of life, followed by marked oscillatory increases and decreases in Sr content for the duration of the fish's life. Small and large forms of Lake Hazen charr of unknown life histories exhibited Sr profiles that were similar to those of the known non-anadromous charr, which strongly suggest that Lake Hazen charr are non-anadromous. These results indicate that Lake Hazen is a "closed" system with energy cycling primarily within the system; this conclusion suggests that a conservative approach would be appropriate for the management of the Lake Hazen charr population.

Habitat use, size and age structure in sympatric brown trout (Salmo trutta) and Arctic charr (Salvelinus alpinus) stocks: resistance of populations to change following harvest

Abstract– Habitat use and population dynamics in brown trout Salmo trutta and Arctic charr Salvelinus alpinus were studied in an oligotrophic lake over a period of 10 years. Previous studies showed that the species segregated by habitat during summer. While brown trout occupied the surface water down to a depth of 10 m, Arctic charr were found deeper with a maximum occurrence at depth 10–15 m. Following the removal of a large number of intermediate sized fish in 1988–89, habitat segregation between the species broke down and Arctic charr were found in upper waters, while brown trout descended to deeper waters. The following year, both species were most frequently found in surface waters at depths of 0–5 m. During the last four years, the species reestablished their original habitat segregation despite another removal experiment of intermediate‐sized fish in 1992–1994. The removal of fish resulted in an increased proportion of large (≥ 25 cm) fish in both species. Furthermore, the charr stock responded by reduced abundance and increased size‐at‐age. The results revealed plasticity and strong resistance to harvest populations of brown trout and Arctic charr. This is probably due to internal mechanisms of intraspecific competition within each population, which result in differential mortality among size classes.

Migration and life history variation in Arctic charr, Salvelinus alpinus

Migratory and non-migratory forms have been observed in many salmonoid fishes including Arctic salmonids and coregonids. To test the hypothesis that migratory populations of Arctic charr, Salvelinu...

Growth and development of a bimodal length–frequency distribution during smolting in a wild population of white-spotted charr in northern Japan

Growth and development of a bimodal length–frequency distribution during smolting in a wild population of white-spotted charr in northern Japan

A phylogeographic survey of brook charr (Salvelinus fontinalis) in Algonquin Park, Ontario based upon mitochondrial DNA variation

Forty-nine populations of brook charr (Salvelinus fontinalis) from Algonquin Park lakes and rivers were analysed for mitochondrial DNA variation. Haplotypic distributions of wild fish in the Algonquin Park region of Ontario, Canada, predominantly reflect postglacial dispersal patterns into the region in spite of substantial hatchery plantings. Two major refugial groupings colonized this regions. Northern and eastern watersheds (Amable du Fond, Bonnechere, and northern Petawawa), were colonized primarily by haplotype 1 fish (B1 phylogenetic assemblage), while Oxtongue River, southern Petawawa, and York River populations were colonized predominately by fish from the B2 and A mtDNA phylogenetic assemblages. Fish with haplotypes in the A and B2 phylogenetic assemblages are common in the Lake Huron drainage. All watersheds in the Park drain into the Ottawa River, except the Oxtongue drainage (part of the Lake Huron watershed). This suggests that early glacial outflows south of the Algonquin Park region (Kirkfield-Trent) may have been colonized by fish that initially invaded 'Ontario island' (south-western Ontario), while fish which invaded northern Algonquin Park were derived from a different refugial grouping(s) which may have involved colonization both up the Ottawa River drainage, and/or from a more westerly (Mississippian) refugial grouping. A majority of the populations in Algonquin Park have been planted with hatchery reared brook charr since the 1940s. The Hills Lake or 'Domestic' strain was used almost exclusively for these plantings. Comparisons of mtDNA haplotypic distributions in hatchery and wild fish suggests that hatchery females had minimal spawning success and/or their progeny had poor survivorship in the wild.

Parasitological evidence for specialized foraging behavior in lake-resident Arctic char (Salvelinus alpinus)

Analyses of statistical associations between the stomach contents and endoparasites of Arctic char, Salvelinus alpinus, from a small (9 ha) lake in northern Quebec revealed that food items found in fish stomachs at the time of capture frequently consisted of intermediate hosts for the parasites infecting the fish. Thus the stomach contents of Arctic char infected by Diphyllobothrium ditremum, D. dendriticum, and Eubothrium salvelini tended to include copepods, while fish infected by the digenean Crepidostomum farionis more frequently contained insect larvae (ephemeropterans) and fish infected by the acanthocephalan Echinorhynchus lateralis most often had amphipods in their stomachs. Moreover, strong quantitative associations were evident between parasites utilizing intermediate hosts from either the benthic or the limnetic zone of the lake. This suggests that some degree of persistent feeding specialization was present among members of the Arctic char population over an extended period of time, with individual fish predominantly feeding upon prey organisms in either limnetic or benthic habitats. In this manner an allopatric Arctic char population may function analogously to more diverse fish communities, where specialist foraging behavior is developed to most efficiently exploit the food web.

Seasonal changes in hypoosmoregulatory ability in landlocked and anadromous populations of Arctic charr, Salvelinus alpinus, and Atlantic salmon, Salmo salar

Seasonal changes in hypoosmoregulatory ability were compared in landlocked and anadromous strains of Arctic charr and Atlantic salmon. Seawater adaptability was assessed using periodic 48 h seawater challenge tests with 25‰. seawater. The landlocked strains of Arctic charr, two from northern Sweden and one from Southern Norway, displayed similar seasonal changes in seawater adaptability as the anadromous strain. Seawater tolerance increased during spring and remained high until the end of July — early August after which it declined. The two strains of Atlantic salmon displayed different seasonal patterns in hypoosmoregulatory ability. The anadromous strain showed a pronounced seasonal pattern with maximal seawater adaptability in early June. In contrast, seawater tolerance in the landlocked strain improved steadily during spring and remained high until late autumn. During the period of enhanced seawater tolerance, hypoosmoregulatory ability increased significantly with body size in both Arctic charr and anadromous Atlantic salmon. The minimum size at which fish were able to regulate plasma sodium following seawater transfer at a level comparable to freshwater levels (<170 mmol I−1) differed significantly between anadromous Atlantic salmon (ca. 14 cm) and Arctic charr (ca. 22 cm). The results show that seasonal changes in hypoosmoregulatory ability are present in both Atlantic salmon and Arctic charr, and that these physiological traits are retained in the corresponding landlocked strains. However, the seasonal pattern of seawater adaptability as well as the minimum size at which seawater tolerance occurs differs between the two species.

Genetic Identity of Transplanted Arctic Char: Implications for Restocking Programs

Abstract The Sunapee char (Salvelinus alpinus oquassa), an endemic landlocked Arctic char of Sunapee Lake, New Hampshire, disappeared in the mid-1900s due to competition with introduced fishes. Sunapee char differed from other lacustrine North American Arctic char in their unique coloration, large size, and use of a midlake spawning shoal. Before their disappearance, Sunapee char were stocked in a series of small lakes in Idaho; stocked fish have become reproductively established in Sawtooth Lake. Because fish from Floods Pond, Maine, had been labeled “Sunapee trout,” due to their physical similarity to Sunapee Lake char, we wanted to examine the genetic similarity between these populations. If they were found to be identical, fish from Floods Pond might be usable as a source to reintroduce the subspecies into New Hampshire, Mitochondrial DNA (mtDNA) restriction fragment variation was used to compare Arctic char from Sawtooth Lake, Idaho, with Arctic char populations in Maine, Quebec, New Brunswick, and E...

Differences in response to liming in a lake-dwelling fish community

The Lake Fjorda water system in southern Norway consists of several lakes which exhibit a gradient in acidification. The system is inhabited by populations of brown trout, Arctic char, whitefish, perch, European minnows and Crucian carp. Populations of Arctic char, whitefish and brown trout were nearly wiped out in some of the locations, as a result of acidification, In 1985, Lake Fjorda was limed in order to improve water quality so the fish community would be recovered. Fish stock assessment by means of gill-net fishing in the epibenthic and pelagic zones was carried out before (1983) and three years after liming (1991–1993). Populations of Arctic char and whitefish have not recovered after eight years of liming. Brown trout are almost extinct and do not seem to be recovering. Perch were less affected by acidification, exhibiting good recruitment also before liming.

Piscivory and cannibalism in Arctic charr

Piscivory and cannibalism in Arctic charr, Salvelinus alpinus, were studied in three lakes in northern Norway: Guolasjavri, which contains only charr, Takvatn, where Arctic charr coexist with three-spined sticklebacks, Gasterosteus aculeatus and brown trout, Salmo trutta, and Stuorajavri, where whitefish, Coregonus lavarelun dominate a fish community containing six species. The prevalence of piscivory in the Arctic charr populations generally increased with increasing predator size. In all three lakes, many charr larger than 20 cm were piscivorous, but the extent of piscivory and cannibalism varied. The greatest prevalence of cannibalism was found in Guolasjavri, where 27% of charr greater than 20 cm in length had fed upon smaller conspeciflcs. In Takvatn, 5% of charr larger than 20 cm were cannibalistic, and an additional 9% had eaten three-spined sticklebacks. In Stuorajavri, up to 74% of the charr greater than 20 cm had eaten whitefish but cannibalism was not recorded. The possible role of cannibalism in population regulation within Arctic charr populations is considered.

Piscivory and cannibalism in Arctic charr

Piscivory and cannibalism in Arctic charr, Salvelinus alpinus, were studied in three lakes in northern Norway: Guolasjavri, which contains only charr, Takvatn, where Arctic charr coexist with three‐spined sticklebacks, Gasterosteus aculeatus and brown trout, Salmo trutta, and Stuorajavri, where whitefish, Coregonus lavarelun dominate a fish community containing six species. The prevalence of piscivory in the Arctic charr populations generally increased with increasing predator size. In all three lakes, many charr larger than 20 cm were piscivorous, but the extent of piscivory and cannibalism varied. The greatest prevalence of cannibalism was found in Guolasjavri, where 27% of charr greater than 20 cm in length had fed upon smaller conspeciflcs. In Takvatn, 5% of charr larger than 20 cm were cannibalistic, and an additional 9% had eaten three‐spined sticklebacks. In Stuorajavri, up to 74% of the charr greater than 20 cm had eaten whitefish but cannibalism was not recorded. The possible role of cannibalism in population regulation within Arctic charr populations is considered.

Racial differences in eggs and juveniles of Windermere charr, Salvelinus alpinus

At least four races of charr occur in Windermere, the largest natural lake in England: north basin and south basin autumn spawners, north basin and south basin spring spawners. This study examines racial differences between eggs and juveniles, and relates juvenile size and survival to egg size. There were no major differences between races for egg incubation times and the percentage of eggs hatching successfully, the latter being high (mean values 76–96%) with a negligible proportion of abnormal alevins (<0.8%). Although there were no significant differences in the lengths of the female parents, both eggs and alevins were significantly larger for the autumn spawners than the spring spawners. Size differences in alevins, especially live weight, were positively related to egg size but not female parent size. Mean percentage survival for juveniles attaining the independent feeding stage was higher for the progeny of autumn spawners (32%) than spring spawners (3%). Racial differences in the egg and alevin stages therefore appear to have a significant effect on subsequent survival, and could be ultimately responsible for the relatively small proportion of spring spawners (only 4–6%) in the Windermere population of charr.

Racial differences in eggs and juveniles of Windermere charr, Salvelinus alpinus

At least four races of charr occur in Windermere, the largest natural lake in England: north basin and south basin autumn spawners, north basin and south basin spring spawners. This study examines racial differences between eggs and juveniles, and relates juvenile size and survival to egg size. There were no major differences between races for egg incubation times and the percentage of eggs hatching successfully, the latter being high (mean values 76–96%) with a negligible proportion of abnormal alevins (&lt;0.8%). Although there were no significant differences in the lengths of the female parents, both eggs and alevins were significantly larger for the autumn spawners than the spring spawners. Size differences in alevins, especially live weight, were positively related to egg size but not female parent size. Mean percentage survival for juveniles attaining the independent feeding stage was higher for the progeny of autumn spawners (32%) than spring spawners (3%). Racial differences in the egg and alevin stages therefore appear to have a significant effect on subsequent survival, and could be ultimately responsible for the relatively small proportion of spring spawners (only 4–6%) in the Windermere population of charr.

The influence of physical watercourse parameters on the degree of anadromy in different lake populations of Arctic charr (Salvelinus alpinus (L.)) in northern Norway

AbstractThe influence of physical watercourse parameters on the degree of anadromy was studied in 15 lake populations of Arctic charr (Salvelinus alpinus (L.)) in northern Norway. The anadromy of the different populations was scored based on the following criteria; marine parasites. fish length and length at maturity. There were significant negative correlations between the anadromy scores and both the length of the outlet rivers of the different lakes and a migration barrier index for the different watercourses (combining migration distance and water velocity). It is hypothsized that these correlations were due to differences in energy expenditure for charr during upstream migration and/or differences in predation pressure on charr during river migration. Short rivers with relatively high water velocity seem to be the most preferable conditions for the anadromous life‐history strategy. There were no correlations between the degree of anadromy and mean river slope or minimum summer water discharge.

Influence of Parr Growth, Lake Morphology, and Freshwater Parasites on the Degree of Anadromy in Different Populations of Arctic Char (Salvelinus alpinus) in Northern Norway

Anadromy of nine lake populations of Arctic char (Salvelinus alpinus) in northern Norway was scored on the following criteria: prevalence of marine parasites, fish size, and size at maturity. In general, anadromy dominated in shallow lakes and residency dominated in deep lakes. The anadromy scores of the populations were significantly higher in lakes without a profundal zone compared with lakes with a profundal zone. There was also a significant negative correlation between the relative volume of the profundal zone (RPV) and the degree of anadromy and between RPV and mean parr length at ages 2+ and 3+. However, differences in parr growth could not explain all the observed variation in anadromy, and the correlation between mean parr length at ages 2+ and 3+ and the degree of anadromy in the different populations was not significant. In addition to the effect on parr growth, lake morphology seemed to influence the degree of anadromy through the relative size of different habitats, which in turn affects the number of available niches. The parr weight/length relationship and infection with the freshwater parasites Phyllodistomum umblae and Diphyllobothrium spp. did not affect the degree of anadromy.

Effects of stocking of piscivorous brown trout, Salmo trutta L., on stunted Arctic charr, Salvelinus alpinus (L.)

AbstractTo study the effects on a stunted freshwater population of Arctic charr, Salvelinus alpinus (L.), two groups of large (26–45 cm) individually tagged brown trout, Salmo trutta L., were released and recaptured with gillnets after 1, 7, 11 and 63 weeks. One group of trout was trained on a fish diet before release, and the other, reared on commercial dry pellets, served as a control. Specific growth rates in both groups were negative 1 week after release and approached zero after 63 weeks. Condition factor and internal fat content decreased during the experiment. Although only 11% of the trout stomachs examined contained fish prey, charr represented 79% of the total stomach weight content. Gillnet samples of charr before and 63 weeks after the release of trout indicated a decreasing population size of charr. Individual growth and mean length of charr increased after release of trout, especially for charr at age 4 years. After the release of trout, 35% of the charr were longer than 20 cm as compared with 6% before the release.

Growth and Sex Distribution in an Anadromous Population of Arctic Char in Northern Norway

Abstract Presmolt Arctic char Salvelinus alpinus in the River Halselva watershed, northern Norway, were analysed with respect to growth and sex distribution. Two main hypotheses were tested: (1) females dominate among the first-time sea migrants; and (2) age at smoltification depends on presmolt growth rate. Our results showed no significant difference in sex distribution of first-time migrants. There was a low frequency of early maturing males in the population, and no differences between the sexes with respect to early sexual maturation were observed. The first-time sea migrants showed a higher presmolt growth rate than the nonmigrating parr in Lake Storvatn, the only lake of the Halselva watershed. Based on both the low frequency of mature pan and the sex ratio in the smolt run, the population of Arctic char in the profundal zone in Lake Storvatn is predominantly anadromous fish. These fish migrate to sea at a greater age than the first-time migrants observed in the River Halselva and are thus “tempora...

Evolution of the life history of Arctic charr Salvelinus alpinus

Arctic charrSalvelinus alpinus life histories are very variable, both within and between localities. In some lakes we find more than one phenotype (in Lake Thingvallavatn there are four), each phenotype having a characteristic life history. In spite of this, the life histories of 44 populations of Arctic charr from throughout its range of distribution can be described accurately by a number of dimensionless indices made up from some common life-history descriptors (age and length at maturity, theoretical maximal length, instantaneous rate of natural mortality). This is contrary to what we previously have found for Brown troutSalmo trutta and we discuss this difference. We also test a new model which seeks to predict reproductive effort based on information on relative length at maturity (Lα)/Linf) and age at maturity. The model did not fit the observed reproductive investment data.

Growth and Age Distribution of a River-Dwelling and a Lake-Dwelling Population of Anadromous Arctic Char at the Same Latitude in Norway

Two populations of anadromous Arctic char Salvelinus alpinus at the same latitude (67°N) in Norway were studied from 1975 to 1989. River Beiarelva Arctic char stay for the entire freshwater portion of their lives in the main river in running water. The Saltdal Arctic char mainly spawn, and the young stay until smoltification, in a lake that drains to the River Saltdalselva. The river-dwelling Arctic char grow better and smoltify at a lower age and at a smaller size than the lake-dwelling fish. They also reach maturity at a lower age, but at the same size as the lake-dwelling Arctic char. In both rivers, Atlantic salmon Salmo salar and anadromous brown trout Salmo trutta are the predominant fish species. The study demonstrated that anadromous Arctic char may exist sympatrically with Atlantic salmon and brown trout in running water. In the watershed where a lake is available, most of the Arctic char stay in the fake in spite of the better growth and lower smolting age that they might attain in running water.