Anadromous Charr Research Articles

Emergence of Potential Anadromous Arctic Charr (Salvelinus alpinus) Habitats in the Svalbard Archipelago After the End of the Little Ice Age

AbstractGlaciers in the Svalbard Archipelago are retreating rapidly in response to climate change. This retreat leads to the alteration of the hydrological and thermal regimes of freshwater ecosystems. In this delicate context, existing anadromous Arctic charr (Salvelinus alpinus) populations are at severe risk and might disappear from the archipelago. However, the retreat of glaciers also promotes the formation of new lake systems that might be suitable for colonization by anadromous Arctic charr. These systems may provide a substantial opportunity for the establishment of new populations of anadromous charr, potentially buffering the decline in existing systems. To date, there is a lack of information on the number of recently deglaciated lake systems that have emerged since the end of the Little Ice Age (ca. 1920) that might be suitable for charr colonization. Therefore, the goal of this paper is to provide an initial assessment of the number of these lakes. To this end, and in accordance with previously published research, this study assesses whether a recently deglaciated lake system is potentially open to colonization based on gradient, river length, and lake surface area. Depending on the applied threshold (four in total), up to 24 lake systems are classified as potentially open to colonization by anadromous Arctic charr, with Spitsbergen emerging as a potential hotspot for colonization. The findings of this paper might serve as basis for new studies and for implementing proactive management and conservation strategies to protect anadromous charr populations.

Diverse migration patterns of anadromous white-spotted charr Salvelinus leucomaenis revealed from otolith microchemistry

Anadromous migration of salmonid fish has been extensively studied, primarily focusing on the dichotomous framework of anadromy and residency. However, there remains a limited understanding of intermediate migratory behaviors within the anadromous framework. Our study aimed to classify the lifetime migration patterns of the anadromous white-spotted charr Salvelinus leucomaenis within and among populations using otolith annuli and Sr:Ca ratios. Initially, the migratory histories of anadromous charr were divided into two stages: “virgin sea-run stage” and “veteran sea-run stage”. The former was further categorized into three types: ocean entry at age ≥1+ years old, early descending, and brackish use. The latter was grouped into four types: annual migrants, frequent migrants, retired migrants, and ocean residents. We found that the proportion of migration patterns varied among rivers, with multiple patterns coexisting within the same river. Migration patterns typically involving 1–5 years spent in freshwater rivers followed by annual oceanic migrations were the most abundant, although diverse patterns were also observed. In the virgin sea-run stage, some individuals experienced the ocean at age 0+ years or brackish environments before their first sea entry. In the veteran sea-run stage, we found individuals who had resided in either the ocean or rivers for over a year. Retired migrants, characterized by stopping oceanic migration at a certain age and subsequently spending time in rivers, were exclusive to southern rivers. Conversely, ocean residents who spend one or more years in the ocean were more frequent in northern regions. Consequently, the lifetime migration patterns of anadromous white-spotted charr may exhibit stronger ocean dependency at higher latitudes. The implications of this study highlight the complexity and flexibility of migratory behaviors within and among white-spotted charr populations.

Variation in personality shaped by evolutionary history, genotype and developmental plasticity in response to feeding modalities in the Arctic charr

Animal personality has been shown to be influenced by both genetic and environmental factors and shaped by natural selection. Currently, little is known about mechanisms influencing the development of personality traits. This study examines the extent to which personality development is genetically influenced and/or environmentally responsive (plastic). We also investigated the role of evolutionary history, assessing whether personality traits could be canalized along a genetic and ecological divergence gradient. We tested the plastic potential of boldness in juveniles of five Icelandic Arctic charr morphs ( Salvelinus alpinus ), including two pairs of sympatric morphs, displaying various degrees of genetic and ecological divergence from the ancestral anadromous charr, split between treatments mimicking benthic versus pelagic feeding modalities. We show that differences in mean boldness are mostly affected by genetics. While the benthic treatment led to bolder individuals overall, the environmental effect was rather weak, suggesting that boldness lies under strong genetic influence with reduced plastic potential. Finally, we found hints of differences by morphs in boldness canalization through reduced variance and plasticity, and higher consistency in boldness within morphs. These findings provide new insights on how behavioural development may impact adaptive diversification.

The comparative lake ecology of two allopatric Arctic Charr, Salvelinus alpinus, populations with differing life histories in Cumberland Sound, Nunavut

The lake ecology of high-latitude fishes is strongly influenced by seasonal feeding opportunities and environmental stochasticity in Arctic environments. Arctic Charr (Salvelinus alpinus (Linnaeus, 1758)) populations are prevalent throughout the Arctic and show multiple life history strategies across their range. Unlike Old World populations, the lake ecology of Arctic Charr populations on south Baffin Island remains poorly defined. We examined the comparative seasonal lake ecology of two differing Arctic Charr populations (anadromous and landlocked) in Cumberland Sound, Nunavut. Anadromous Charr showed no evidence of feeding occurring within freshwater once they began seaward migrations. Anadromous Charr achieve sexual maturation at a larger size and younger age than landlocked Charr. Landlocked Charr used more lake habitats than anadromous Charr with feeding opportunities as an apparent influence on habitat selection. Landlocked Charr fed year round. They adopted a cannibalistic feeding strategy in the winter but consumed a variety of prey items in the fall. Littoral habitat was found to be important to all sizes of Charr in both seasons. Smaller anadromous Charr (<350 mm) did not use the benthic habitat. The variable ecology and form demonstrated further emphasizes the phenotypic adaptability of Arctic Charr that allows its widespread distribution in the Arctic.

Temperature preference of juvenile Arctic charr originating from different thermal environments

Temperature preference of juvenile (age 1+) Arctic charr (Salvelinus alpinus L.) originating from four arctic and sub-arctic populations (Svalbard and mainland northern Norway), representing a range of habitats with different temperature conditions, was studied by use of a shuttle-box system which allowed individual fish to control their environmental temperature. Based on the assumption that adaptations to long-lasting differences in thermal environments would affect temperature preference, we expected that Arctic charr from the high arctic Svalbard would prefer a lower temperature than the charr from two well-studied sub-arctic mainland lakes (i.e. one anadromous charr population from Storvatn, Hammerfest and two sympatric resident charr morphs from Fjellfrosvatn, Malselv). There were, however, no significant differences in temperature preference among the four populations after 24 h exposure to the shuttle-box system, although the charr from the omnivore upper-water sympatric morph of Fjellfrosvatn used significantly longer time to reach a stable thermal preferendum than the fish of the other populations. The average temperature preference at the end of the trials ranged between 10.9 and 11.6 °C among the populations. The lack of population differences suggests that temperature preference is not a polymorphic trait under strong selection in Arctic charr.

Data limited assessment of selected North American anadromous charr stocks

Charr populations are particularly susceptible to change, either from the application of harvest or environmental conditions such as climate variation. As an alternative to conventional fishery analysis, we analyze the sustainability and viability of selected North American charr stocks using a number of approaches. We compare several methods for data limited situations to determine the allowable harvest of the Ekalluk River, Paliryauk River, Halovik River, Jayco Lake and Lauchlan River Arctic Charr including Cadima’s Maximum Sustainable Production Method, Hierarchical Bayesian Surplus Production Models, a Status Quo Total Allowable Harvest method, Long-term Average Catch methods and the Depletion-Corrected Average Catch method. Each method provided a similar outcome in terms of the relative importance of stocks to the fishery. The predicted sustainable harvest of larger stocks such as the Ekalluk and Jayco varied more according to the method applied than the other stocks studied. While not a replacement for more comprehensive fishery models these methods can be useful in data poor situations.

Long-term fasting in the anadromous Arctic charr is associated with down-regulation of metabolic enzyme activity and up-regulation of leptin A1 and SOCS expression in the liver.

The life strategy of the anadromous Arctic charr (Salvelinus alpinus) includes several months of voluntary fasting during overwintering in freshwater, leading to emaciation prior to seawater migration in spring. In this study we compared changes in condition, substrate utilization and liver metabolism between captive anadromous charr subjected to food deprivation during late winter and spring, and conspecifics fed in excess. In March, nine out of the 10 sampled fed fish had not eaten, indicating that they were in a voluntary anorexic state. In June, the fed fish were eating and all had higher body mass, condition factor and adiposity than in March. In fasted fish there were only small decreases in body mass, condition factor and adiposity between March and May, but all these parameters decreased markedly from May to June. The fasted fish were depleted in fat and glycogen in June, had suppressed activity of hepatic enzymes involved in lipid metabolism (G6PDH and HOAD) and seemed to rely on protein-derived glucose as a major energy source. This was associated with upregulated liver gene expression of leptin A1, leptin A2, SOCS1, SOCS2 and SOCS3, and reduced IGF-I expression. In an in vitro study with liver slices it was shown that recombinant rainbow trout leptin stimulated SOCS1 and SOCS3 expression, but not SOCS2, IGF-I or genes of enzymes involved in lipid (G6PDH) and amino acid (AspAT) metabolism. It is concluded that liver leptin interacts with SOCS in a paracrine fashion to suppress lipolytic pathways and depress metabolism when fat stores are depleted.

Comparative transcriptomics of anadromous and resident brook charr Salvelinus fontinalis before their first salt water transition

Abstract Most salmonid taxa have an anadromous life history strategy, whereby fish migrate to saltwater habitats for a growth period before returning to freshwater habitats for spawning. Moreover, several species are characterized by different life history tactics whereby resident and anadromous forms may occur in genetically differentiated populations within a same species, as well as polymorphism within a population. The molecular mechanisms underlying the physiological differences between anadromous and resident forms during the first transition from freshwater to saltwater environments are only partially understood. Insofar research has typically focused on species of the genus Salmo. Here, using a 16,000 cDNA array, we tested the hypothesis that ana-dromous brook charr Salvelinus fontinalis are characterized by differences in their transcriptome relative to resident brook charr before the anadromous fish migration. Families originating from parapatric populations of anadromous and resident charr were reared in controlled environments mimicking natural temperature and photoperiod, and sampled in spring, while still in fresh water. While anadromous and resident charr showed similar transcriptome profiles in white muscle, they were characterized by striking differences in their gill transcriptome profiles. Genes that were upregulated in the gills of anadromous charr were principally involved in metabolism (mitochondrial electron transport chain, glucose metabolism, and protein synthesis), development (tissue differentiation) and innate immunity. We discuss the nature of these transcriptomic differences in relation to molecular mechanisms underlying the expression of anadromous and resident life history tactics and suggest that the anadromous charr express some of the molecular processes present in other migratory salmonids.

Hans Nordeng: a man of principles

Professor, cand. real. Hans Nordeng died in Baerum, Norway in May 2010, at the age of 91 years. He was an extraordinary man; an unconventional, creative and hard-working scientist, and a very gifted teacher and tutor. Most of his publications were based on many years of research, often combining extensive field work and carefully planned experiments and transplantations (Vollestad and Skurdal 1994). Several of them contributed significantly to the fields of fish ecology and evolution. He kept a glowing enthusiasm for fish biology until a great age, publishing his last paper when he was 91 (Nordeng 2009). He grew up in Salangen, Northern Norway, close to the river that was to become the primary research system of his career. As a young recruit at an under-officer school, he fought in the battle at the Narvik-Gratangen front of World War II in the spring of 1940. He started a military career after the war but later went to university as a grown-up man. After graduation, he held an assignment with the Institute of Marine Research in Bergen before taking up a lectureship at the University of Oslo, a position he kept for most of his active life. Then, after retiring fromOslo, he was appointed as a full professor at the University of Tromso, finally achieving the personal chair he so much deserved. He served in this position for 2 years. Hans Nordeng published several innovative and influential papers. Two of them will always be tied to his name. The first, published in Nature (Nordeng 1971), proposed a pheromone hypothesis to explain the population specific homing of anadromous fishes to their native river. It was based on transferring fertilized eggs of anadromous arctic charr (Salvelinus alpinus) from the Salangen River system to a hatchery at Voss, south-west Norway (south of the range of anadromous charr), rearing the fish to the smolt stage (4 years), flying them back to northern Norway and releasing them in the estuaries of the Salangen River and a neighbouring river. These fish had experienced no olfactory cues from their home river water during rearing. Yet almost all the fish that were released in Salangen and the majority of the fish released in the other river, returned to the Salangen River. This strongly suggested that population specific pheromones, possibly bound to the skin mucus, provided the olfactory cues for homing; not the river water itself. He established important co-operation with physiologists to test the hypothesis (Doving et al. 1974), and successive pheromone research included several other migratory fish species. The second paper (Nordeng 1983) was based on his long-term studies of three sympatric Environ Biol Fish (2011) 91:367–368 DOI 10.1007/s10641-011-9793-3

Maturation, growth and fecundity of Arctic charr, Salvelinus alpinus (L.), life-history variants co-existing in lake systems of Southern Baffin Island, Nunavut, Canada

Two life-history variants of Arctic charr (Salvelinus alpinus), anadromous and lake-resident, have been previously identified in lakes of Southern Baffin Island, Nunavut, Canada. In accordance with classical life-history theory, it is hypothesised that anadromous charr will delay maturation in both size and age, and have increased fecundity (per spawning event) in comparison with lake-resident charr. Sagittal otoliths and biological data were collected for both life-history variants within the three studied lakes: Iqalugaarjuit, Qasigiat and Qinngu. Sagittal otoliths were embedded in epoxy resin, cross-sectioned for age determination, and imaged for back-calculation (size and age). Back-calculated data in each lake were fit to von Bertalanffy growth models for each life-history variant and compared via analysis of residual sums of squares. Anadromous charr had greater mean size at maturity and experienced a delay in mean age at maturity in comparison with lake-residents. The relationship between size and fecundity or egg diameter did not differ between the two life-history variants. Growth models indicate that the overall growth coefficients of lake-resident and anadromous charr were different in all three studied lakes. The Brody growth coefficient for all lake-resident charr populations was greater than anadromous individuals indicating that maximum length was reached at a rapid rate, resulting in a smaller asymptotic length. Indirect evidence suggests that anadromous and lake-resident charr belong to one reproductive population. Future genetic analysis is necessary to further determine the degree of divergence between the life-history variants.

High lacustrine gillnet catchability of anadromous Arctic charr

Arctic charr is the only freshwater fish in most of the High Arctic, with both resident, anadromous, and landlocked populations present. The anadromous Arctic charr is particularly highly sought-after, and has been an important food source for people living in Arctic regions. A recent decline in harvest in many areas has been related to over-exploitation by extensive gillnetting. Very few studies, if any, have estimated the gillnet efficiency for harvesting anadromous Arctic charr. In this study, all anadromous Arctic charr ascending the lake, Linnevatn, in western Spitsbergen, Svalbard, were marked over a period of 5 weeks, in July–August 2008. Recaptures in the lake were obtained by gillnetting with three mesh sizes (39, 45, and 52 mm measured knot-to-knot) during three periods. The total number of anadromous charr in the lake was estimated by both Schnabel and Petersen mark-recapture methods. The catchability increased significantly with fish size. Anadromous charr in the length-class 40.0–56.9 cm captured by the legal mesh size in Svalbard lakes (52 mm) had a mean catchability of 0.0023 per gillnet per 2 h fishing effort, and the catch quota which is set at 40 charr for Linnevatn by the Governor of Svalbard, would have been filled by less than five gillnets, each used for 6 h. Although this short fishing time may give an overestimation of catchability due to the avoidance of gear saturation, the high catchability values still indicate that anadromous Arctic charr populations may be extremely vulnerable to gillnetting. Hence, in addition to catch quotas set for each population, a restriction on the number of gillnets allowed per harvester should also be considered.

Latitudinal variation in growth among Arctic charr in eastern North America: evidence for countergradient variation?

Biological data from 66 populations of Arctic charr, Salvelinus alpinus, from eastern North America were analysed to test the applicability of the countergradient hypothesis as an explanation of differences in seasonally adjusted growth rates. Samples were obtained along a 37° latitudinal gradient and partitioned among anadromous, normal lacustrine, and dwarf lacustrine Arctic charr morphotypes. Models relating length-at-age or age-specific growth rates to latitude were estimated for each morphotype. Length-at-age declined with latitude for anadromous and lacustrine charr. Age-specific growth rates also varied with latitude, particularly for normal lacustrine charr. Results of analyses provide support for the countergradient hypothesis in growth performance of normal lacustrine morphotypes, where northern populations compensate for the shorter growth season with a greater rate of growth than southern populations. Anadromous charr exhibited equivocal evidence of countergradient variation, while results for dwarf lacustrine Arctic charr populations were inconclusive owing to the limited range of ages, and latitudes for which data were available.

Resilience and stability of north Labrador Arctic charr, Salvelinus alpinus, subject to exploitation and environmental variability

There are relatively few studies that have examined in detail the effects of long term exploitation on population characteristics of Arctic charr, Salvelinus alpinus, coincident with natural changes in environmental conditions. This is particularly the case for anadromous charr despite their widespread use and importance in areas such as northern Canada. Here, the response of north Labrador charr to major reductions in commercial exploitation following long periods of intense fishing is described for three stock complexes with emphasis on changes in size, growth, and age configurations. Changes in age and size distribution, specifically long-term declines in weight, are linked with periods of intensive exploitation and possibly with variability in the climate of the northwest Atlantic that resulted in identifiable diet shifts during the early 1990s. Despite observed changes in some metrics, populations have maintained relatively stable length compositions with variations in weight showing resilience to return to earlier configurations as exploitation was reduced and environmental conditions ameliorated. Results of the long-term investigations challenge traditional beliefs associated with the inability of all anadromous charr to withstand periods of intense exploitation.

Temporal and Spatial Habitats of Anadromous Brook Charr in the Laval River and its Estuary

Anadromy in brook charr occurs across the species’ range, but few studies have examined contiguous seasonal movements and habitat utilization of freshwater and estuarine environments. We used acoustic telemetry to track movements of anadromous brook charr for 1 year in the Laval River, Quebec. Fish entered the marine environment in May and June, inhabited shallow (<1.7 m), near-shore areas (<500 m from shore), and rarely ventured beyond the headlands of the bay. They were found where salinities were 1–34 ppt and temperatures 5–18°C. There was a strong tidal periodicity to observed movements with fish running up into bays as they became inundated at high tide and then returning to deep river channels in the bays at low tide. Between late July and early September, the charr returned to freshwater and spawned in the middle and upper sections of the river in October and November. Winter habitats were dispersed over 22 km of the river including two lakes. These detailed observations are an important contribution to our understanding of the evolutionary significance of anadromy in this species. The salinity and temperature co-tolerance provides insights into the species’ post-glacial dispersal, present-day distribution, and potential habitat maps for conservation, restoration, and enhancement programmes.

Growth and diet of anadromous Arctic charr after their return to freshwater

Abstract –The post smolt of anadromous Arctic charr (Salvelinus alpinus) from Lake Storvatn, northern Norway (70°39′48″), continued to feed and grow after their return to freshwater in late summer, but in late autumn (October) both their growth rate and feeding intensity ceased along with the drop in water temperature. In contrast, adult, sexually mature anadromous charr did not appear to feed during their freshwater residency. The stomach fullness of post smolts were similar to that of resident Arctic charr during early autumn, and their diets were similar, being dominated by pelagic prey such as surface insects,Holopediumsp.,Bosminasp. and chironomid pupae. Later in the autumn, the resident charr also included some more benthic prey, in particular gastropods, whereas the post smolts continued to feed predominantly on zooplankton and surface insects, but with a lower stomach fullness than the resident fish. This suggests that after arrival in freshwater, the post smolts continue their pelagic feeding behaviour displayed during the sea‐migration.

The growth history of anadromous white-spotted charr in northern Japan: a comparison between river and sea life

The growth history of anadromous white-spotted charr in northern Japan: a comparison between river and sea life

Seawater tolerance in captive high-Arctic Svalbard charr (Salvelinus alpinus): effect of photoperiod and body size

Anadromous Arctic charr (Salvelinus alpinus) returning after spending summer at sea were captured in a fish trap in the Dieset River on Spitsbergen (79°10′N), Svalbard. Fish selected for breeding were transported to Trondheim in mainland Norway. Eggs obtained from the charr were fertilized and incubated in total darkness. First-fed alevins and resulting parr were kept under continuous light until an age of 0+ and 1+ years, respectively. Some 1+ charr were kept as controls under a continuous short-day photoperiod (6L:18D) from autumn until the end of the experiment the following July. Charr aged 0+ and 1+ years old were exposed to a short-day photoperiod from October until January and a simulated natural photoperiod for 80°N from January until the end of the experiments. Challenge tests demonstrated a size-dependent seawater tolerance for charr with a body length less than 18 cm. Fish smaller than 12 cm did not survive the 96-h test period. The larger charr kept under simulated natural photoperiod developed increased hypoosmoregulatory capacity. Charr kept under short-day treatment showed a slight, short-lived increase in seawater tolerance. A 7-days seawater challenge test at the end of the experiment (July) demonstrated that the anticipatory seawater preparation in charr is influenced by photoperiod. We conclude that offspring from anadromous high-Arctic charr must achieve a threshold body size (>25 cm) before they can respond to photoperiod signals which trigger the development of the hypoosmoregulatory capacity typical for smoltifying salmonids.

Life-history Traits of Charr, &lt;i&gt;Salvelinus alpinus&lt;/i&gt;, from a High Arctic Watercourse on Svalbard

Three arctic charr (Salvelinus alpinus) morphs coexist within the Dieset watercourse (79°10'N, 11°20'E) on Spitsbergen, Svalbard. Small freshwater resident charr exhibited a very slow growth rate, while large freshwater resident charr grew at a rate comparable to that reported for cannibalistic charr elsewhere. First-time sea migrants of the anadromous charr were similar in size to their more southern-living Norwegian conspecifics, but on average two years older. The average number of sea runs before first-time spawning was 3.6 for males and 4.4 for females. Veteran migrants displayed growth comparable to that of anadromous charr from more southern populations. In all three morphs, sex ratio did not differ from unity. The short-lived small residents matured from an age of 4 years, 3 to 4 years earlier than did large residents and anadromous charr. The majority of small resident and anadromous charr spawn a maximum of three times, while large resident charr may spawn up to seven times. Although 69% of large resident charr were older than 15 years, only 5.7% of reproductive anadromous charr exceeded this age. This divergence may indicate different reproductive strategies between the two morphs. There was no evidence of reproductive isolation between these High Arctic charr morphs.

Comparison of growth, diet and food consumption of sea‐run and lake‐dwelling Arctic charr

Sea‐run post‐smolt Arctic charrSalvelinus alpinus, (15–26 cm) from Storvatn, northern Norway (70°39′48″N) had significantly higher average specific growth rates in two years (1·64 and 1·66) than the corresponding lake‐dwelling charr (0·53 and 1·20). The post‐smolts displayed fast compensatory growth in the first 2–3 weeks of their sea residency, but then almost stopped growing prior to their return to fresh water. Lake‐dwelling charr grew more evenly during the same time period. Thus, the anadromous charr may return to the lake after only 5–6 weeks in the sea, because the potential to maintain a high growth rate in the sea is reduced. The marine diet consisted mainly of the two crustacean plankton speciesCalanus finmarchicus, andThysanoëssa, sp. (88%), and less of fish (6%), insects (4%) and benthos (2%). The diet of lake‐dwelling charr consisted mainly of insects (58%, mostly chironomid pupae) and zoobenthos (29%), and less of zooplankton (13%) during the same time period. Although post‐smolts had the highest growth rates, they had significantly lower food consumption rates and higher frequencies of empty stomachs than the corresponding lake‐dwelling fish. Possible explanations for this paradox are discussed in relation to stomach evacuation rates, water temperature, feeding behaviour and the energy content of the food in the two environments.

Contrasts in osmoregulatory capacity of two Arctic charr, Salvelinus alpinus (L.), strains from northern Norway

The osmoregulatory capacities of two north Norwegian strains of Arctic charr, Salvelinus alpinus L., have been compared. Groups of fish were either held in fresh water from late-February to September, or were exposed to full-strength sea water (33–34‰) during the period (mid-May–late-June) at which anadromous charr would usually be at sea. The charr (4+ years old, 400 g initial body weight) used in the experiment were all hatchery-reared fish, either of an anadromous strain originating from the Hammerfest area (70°N), or of a landlocked strain originating from the Skjomen area (68°N). The growth of the two strains of charr was similar for fish held in fresh water. There were temporal changes in gill Na +/K +-ATPase activity and chloride cell numbers that seemed to be typical of a parr-smolt transformation, but charr of the landlocked Skjomen strain were not able to osmoregulate effectively and survive in sea water. Fish of the anadromous Hammerfest strain displayed increased gill Na +/K +-ATPase activity following transfer from fresh water to sea water in May. Charr of this strain were able to regulate plasma osmolality and plasma ion concentrations, and grew at similar rates to the fish maintained in fresh water. The results show that there are distinct differences in osmoregulatory capacity between fish of the anadromous Hammerfest strain and charr of the landlocked Skjomen strain.