Salvelinus Malma Research Articles

INFLUENCE OF SUSPENDED FLUVIAL SEDIMENTS ON THE RIVER ICHTHYOCENE

Published data on direct and indirect impacts of suspended matter on freshwater fish are overviewed, both for short-term (hours) experiments and long-term (weeks and months) monitoring in natural conditions. Lethal or paralethal concentrations of the suspended matter are determined for 18 species from 8 families. Accumulation effect of the permanent concentration is observed for charr Salvelinus malma in the laboratory experiment. The most common fish families of the freshwater ichthyofauna in Russia are ranked by threshold of their sensitivity to suspended matter in the order: sturgeon and catfish (1000 mg/L) — carp (250 mg/L) — perch (100 mg/L) — salmon (10 mg/L, with paralethal concentration 25–35 mg/L). Fish mortality is estimated in dependence on the suspended matter concentration and time of exposure, by species. Environmental consequences of the suspended sediments impact are assessed for fish communities of the rivers of Kamchatka, the Lena River, and the Selenga River.

Substituting fishmeal with extruded soybean meal in diets did not affect the growth performance, hepatic enzyme activities, but hypoxia tolerance of Dolly Varden (Salvelinus malma) juveniles

Extruded soybean meal (ESBM) showed increased digestibility of crude protein, amino acids and fat, better oil retention capacities, attenuated anti-nutrient factor effects and improved its nutritive value compared with raw soybean meal, indicating a promising application prospects for ESBM in fish culture. This study aimed to evaluate the effects of substituting fishmeal with ESBM on growth performance, hepatic antioxidant capacity and the resistance to hypoxia stress on juvenile Dolly Varden (Salvelinus malma). Five hundred and forty fish were randomly assigned to six groups fed with iso-nitrogenous and iso-energetic diets with ESBM for replacement of 0% (control), 10% (G1), 20% (G2), 30% (G3), 40% (G4) and 50% (G5) fishmeal. After an 81-day feeding trial, groups fed ESBM substituted diets (G2 to G5) showed no significant differences in survival rates, final body weights, weight gain rates, feed conversion ratios, specific growth rates, hepatosomatic indexes and condition factors with the control group (G0), reflecting normal food intake and growth performance. The hepatic enzyme activities of total antioxidant capacity, catalase and superoxide dismutase were not affected by ESBM substituted diets, showing no harmful effects on ROS eliminating abilities. Hepatic HSP70 expression levels had increased 1.3 times for G5 group, reflecting a less tolerance to hypoxia for fish fed diets with high substituting level of ESBM. In conclusion, replacing, despite 50%, fishmeal with ESBM in diets had no detrimental effects on growth performance and hepatic enzyme activities, but lowering the hypoxia tolerance of juvenile Dolly Varden (Salvelinus malma).

Decoupling of otolith and somatic growth during anadromous migration in a northern salmonid

We assessed the fish length – otolith length relationship (FL–OL) in Dolly Varden (Salvelinus malma malma) to verify proportional growth. A decoupling was detected during first ocean migration where fish growth was occurring at a greater rate than otolith growth. Because of this decoupling, the application of traditional back-calculation models overestimated the size-at-age in premigratory char. We developed modified back-calculation equations from existing traditional models to account for this decoupling based on discontinuous piecewise regressions. The new biological intercept breakpoint method (BI–BP) provided the most accurate representation of fish size-at-age throughout all life history stages when compared with known size-at-capture values in fish. The decoupling indicates that factors other than somatic growth are important for otolith accretion. Physiological changes during smoltification likely alter calcium uptake and thereby affect calcium deposition rates on otoliths during this short but biologically critical time period of life history. It is probable that species exhibiting similar complex ontogenetic shifts in life history will likely exhibit decoupling to some extent in the FL–OL relationship.

Spatiotemporal Variation and Size‐Selective Predation on Hatchery‐ and Wild‐Born Juvenile Chum Salmon at Marine Entry by Nearshore Fishes in Southeast Alaska

AbstractJuvenile Pacific salmon Oncorhynchus spp. experience high mortality at marine entry, yet our quantitative understanding of predation during this critical period is limited. We evaluated spatial, temporal, and size‐based patterns of predation on hatchery‐ and wild‐born juvenile Chum Salmon O. keta by two abundant predators in Southeast Alaska estuaries: the Pacific Staghorn Sculpin Leptocottus armatus and Dolly Varden Salvelinus malma. For the predators we sampled, Chum Salmon comprised 4.5% of the diet by weight for Pacific Staghorn Sculpin (n = 937) and 19.6% of the diet by weight for Dolly Varden (n = 448), with 88% of the individual Chum Salmon consumed originating from hatcheries. Variation in occurrence of Chum Salmon in diets was driven by date, site, and local Chum Salmon density. The quantity of Chum Salmon consumed by Pacific Staghorn Sculpin varied with predator length, Chum Salmon density, and the proportion of hatchery fish present; however, date was the only important predictor for Dolly Varden. The mean length of Chum Salmon in the diets of both predators was significantly shorter than that of concurrent hatchery releases or seine catches, suggesting size‐selective predation on smaller individuals. This pattern indicates that hatchery strategies of releasing larger individuals may reduce the initial vulnerability of hatchery salmon to estuarine predators.

Permafrost Hydrology Drives the Assimilation of Old Carbon by Stream Food Webs in the Arctic

Permafrost thaw in the Arctic is mobilizing old carbon (C) from soils to aquatic ecosystems and the atmosphere. Little is known, however, about the assimilation of old C by aquatic food webs in Arctic watersheds. Here, we used C isotopes (δ13C, Δ14C) to quantify C assimilation by biota across 12 streams in arctic Alaska. Streams spanned watersheds with varying permafrost hydrology, from ice-poor bedrock to ice-rich loess (that is, yedoma). We measured isotopic content of (1) C sources including dissolved organic C (DOC), dissolved inorganic C (DIC), and soil C, and (2) stream biota, including benthic biofilm and macroinvertebrates, and resident fish species (Arctic Grayling (Thymallus arcticus) and Dolly Varden (Salvelinus malma)). Findings document the assimilation of old C by stream biota, with depleted Δ14C values observed at multiple trophic levels, including benthic biofilm (14C ages = 5255 to 265 years before present (y BP)), macroinvertebrates (4490 y BP to modern), and fish (3195 y BP to modern). Mixing model results indicate that DOC and DIC contribute to benthic biofilm composition, with relative contributions differing across streams draining ice-poor and ice-rich terrain. DOC originates primarily from old terrestrial C sources, including deep peat horizons (39–47%; 530 y BP) and near-surface permafrost (12–19%; 5490 y BP). DOC also accounts for approximately half of fish isotopic composition. Analyses suggest that as the contribution of old C to fish increases, fish growth and nutritional status decline. We anticipate increases in old DOC delivery to streams under projected warming, which may further alter food web function in Arctic watersheds.

Features of the Changes in External Morphology and Axial Skeleton in Juvenile Salmonid Fishes (Salmonidae) Associated with Smoltification

Changes in external morphological characters and relative lengths of vertebral centra from different regions of the vertebral column are analyzed during smoltification in wild juveniles of five salmonid fish species: Atlantic salmon Salmo salar, brown trout S. trutta, mikizha Parasalmo mykiss, coho salmon Oncorhynchus kisutch, and northern Dolly Varden Salvelinus malma. The changes in the body proportions and external morphology are similar in different salmonid species, but the patterns of differentiation of the vertebral column’s postanal part are different. In Atlantic salmon, all vertebral centra of the postanal part are subject to elongation; in mikizha and brown trout, a small number of the centra are elongated only in the anterior region of the postanal part; in coho salmon, the centra are elongated in the posterior region of the postanal part; in Dolly Varden, the centra are elongated in the middle region of the postanal part. Thus, despite observed universal changes in external morphology associated with smoltification in the family Salmonidae, the development of future marine migrants' phenotypes is species-specific due to different growth of various groups of vertebral centra in the vertebral column’s postanal part. The possible reasons for the species diversity in the growth of various groups of vertebral centra are discussed.

Aggressive interactions affect foraging and use of space in a drift foraging salmonid, Salvelinus malma (Salmoniformes: Salmonidae)

Abstract Although intraspecific interactions likely affect habitat choice and foraging behaviour in animals, our knowledge regarding how these factors interact is frequently limited to either lab or field studies, but not both. We observed pairs of dominant and subordinate drift-foraging Dolly Varden char (Salvelinus malma) in an Alaskan stream, and quantified intraspecific interactions and foraging behaviour. Dominant individuals had higher foraging rates, occupied slower holding velocities and were displaced shorter distances during bouts compared to subordinate individuals. Individuals initiated bouts more frequently from the downstream position, than from lateral or upstream positions. Dominant individuals were more likely to occupy the upstream position after a bout than subordinates, which ensures that dominants have the first opportunity to capture drifting prey.

Temperature‐dependent competition between juvenile salmonids in small streams

Abstract Biotic interactions affect species distributions, and environmental factors that influence these interactions can play a key role when range shifts in response to environmental change are modelled. In a field experiment using enclosures, we studied the effects of the thermal habitat on intra‐ versus inter‐specific competition of juvenile Dolly Varden Salvelinus malma and white‐spotted charr Salvelinus leucomaenis, as measured by differences in specific growth rates during summer in allopatric and sympatric treatments. Previous laboratory experiments have shown mixed results regarding the importance of temperature‐dependent competitive abilities as a main driver for spatial segregation in stream fishes, and no study so far has confirmed its existence in natural streams. Under natural conditions in areas where the two species occur in sympatry, Dolly Varden dominate spring‐fed tributaries (cold, stable thermal regime), whereas both species often coexist in non‐spring‐fed tributaries (warm, unstable thermal regime). Enclosures (charr density = 6 per m2) were placed in non‐spring‐fed (10–14°C) and spring‐fed (7–8°C) tributaries. In enclosures placed in non‐spring‐fed tributaries, Dolly Varden grew 0.81% per day in allopatry and had negative growth (−0.33% per day) in sympatry, whereas growth rates were similar in allopatry and sympatry in spring‐fed tributaries (0.68 and 0.58% per day). White‐spotted charr grew better in sympatry than in allopatry in both thermal habitats. In non‐spring‐fed tributaries, they grew 0.17 and 0.79% per day and in spring‐fed tributaries 0.46 and 0.75% per day in allopatry and sympatry, respectively. The negative effect of inter‐specific competition from white‐spotted charr on Dolly Varden thus depended on the thermal habitat. However, there was no strong evidence of a temperature‐dependent effect of intra‐ and inter‐specific competition on white‐spotted charr growth. Multiple factors may shape species distribution patterns, and we show that temperature may mediate competitive outcomes and thus coexistence in stream fish. These effects of temperature will be important to incorporate into mechanistic and dynamic species distribution models.

Is Dolly Varden in Arctic Alaska Increasing in Length in a Warming Climate?

AbstractThe body condition, abundance, and size of several vertebrate taxa occupying the Alaskan and Canadian Arctic have increased in this rapidly changing environment. Presently, anecdotal stakeholder reports suggest that anadromous populations of Dolly Varden Salvelinus malma in Arctic Alaska are attaining greater maximum sizes than reported in the past. However, growth analyses have not been conducted for any substantial period of time. To qualitatively examine one facet of growth, we reviewed scientific journal articles, gray literature, and unpublished data for reported maximum lengths of Dolly Varden from the Chukchi and Beaufort seas collected over the past ∼50 y (1969–2015). Regression analyses of maximum length of Dolly Varden from 1969 to 2015 support the observations that the maximum size of this species is likely increasing in a changing Arctic. These results, coupled with the lack of comprehensive growth data, highlight the importance of long-term monitoring of organismal responses to a changing environment and provide valuable direction for future research on this important subsistence resource for Indigenous peoples who inhabit the Arctic.

Mechanics of foraging success and optimal microhabitat selection in Alaskan Arctic grayling (Thymallus arcticus)

Most fishes residing in temperate streams in the Northern Hemisphere are drift-feeders. Despite this fact, little is known about the mechanisms of drift-feeding itself. We used Alaskan Arctic grayling (Thymallus arcticus), an abundant boreal drift-feeder, to examine the effects of water velocity on several aspects of drift-feeding behavior and test predictions of the Grossman et al. (2002) net energy intake model for microhabitat choice. Water velocity had a negative effect on prey capture, a positive effect on holding velocity, and little effect on reactive distance. We also found that dominance was a better predictor of prey capture success than size rank, although neither of these variables influenced holding velocity or reactive distance. The Grossman et al. (2002) model successfully predicted holding velocities of grayling in one Alaskan stream, but not another. Model failure might have occurred due to higher turbulence, increased predation, or interspecific competition with Dolly Varden (Salvelinus malma). These results help inform the study of habitat selection in drift-feeding fishes as well as management and conservation of Arctic grayling.

Seasonal changes in light availability modify the temperature dependence of secondary production in an Arctic stream.

Light and temperature are key drivers of ecosystem productivity, but synchrony of their annual cycles typically obscures their relative influence. The coupling of annual light-temperature regimes also drives complementary seasonal cycles of energy supply (primary production) and demand (metabolism), perhaps promoting temporal stability in carbon (C) storage and food web production that may be difficult to discern in most ecosystems. Spring-fed streams in the Arctic are subject to extreme annual fluctuations in light availability but have relatively stable water temperatures, which allows assessment of the independent effects of light and temperature. We used the unusual annual light and temperature regimes of Ivishak Spring, Alaska, USA (latitude 69°N, annual water temperature range ~4-7°C) to test predictions about the effect of light availability on consumer productivity with minimally confounding effects of temperature. We predicted that (1) annual patterns of secondary production would follow patterns of primary production, rather than temperature, due to organic C limitation during winter darkness when photosynthesis is effectively halted, (2) C limitation would propagate from primary producers upward through several trophic levels, (3) the lack of temperature dependence during winter darkness would be expressed as anomalous Arrhenius plots of growth rates indicating decoupled production-temperature relationships, and (4) consumer diets would reflect C limitation during winter. As predicted, we found (1) lowest production by macroinvertebrates and Salvelinus malma (Dolly Varden char) at the lowest light levels rather than the lowest temperatures, (2) apparent winter C limitation propagated upward through three trophic levels, (3) anomalous Arrhenius plots indicating lack of temperature dependence of consumer growth rates during winter, and (4) lowest consumption of diatoms (by macroinvertebrates) and invertebrate prey (by S.malma) during winter. Together, these results indicate that light drives annual patterns of animal production in Ivishak Spring, with stable annual temperatures likely exacerbating C limitation of ectotherm metabolism during winter. The timing and severity of winter C limitation in this unusual Arctic-spring food web highlight a fundamental role for light-temperature synchrony in matching energy supply with demand in most other ecosystem types, thereby conferring a measure of stability in the metabolism of their food webs over annual time scales.

A spatially-explicit, individual-based demogenetic simulation framework for evaluating hybridization dynamics

Spatially-explicit individual-based simulation models provide a valuable tool for exploring complex ecological and evolutionary processes that are not easily empirically measured. Here, we present modifications of a spatially-explicit individual-based simulation model (CDMetaPOP) to accommodate a two-species system and simulations involving interspecific hybridization. We first describe how a hybrid (H) index is used to distinguish individuals of interspecific descent from those of either parental species. User-defined thresholds provide flexibility in the degree of admixture tolerated for classifying ‘pure’ individuals. We then detail relationships further informed by the H index, including individual growth, temperature-based fitness and selection, and mate preference behavior. Empirically derived species- and system-specific information can be incorporated into these relationships, for example, to produce differential growth among hybrids and parental species. Lastly, we demonstrate an application of this simulation framework by exploring the relative effects of temperature-based selection, mate preference behavior, and hybrid fitness on the rate and spatial extent of sympatric hybridization between two native riverine fish species, bull trout (Salvelinus confluentus) and Dolly Varden (Salvelinus malma), in the upper Skagit River system (United States and Canada). Results from this demonstration provide guidance for future empirical studies of bull trout, a federally threatened species. Understanding factors that contribute to the initiation and maintenance of hybridization, as well as the ecological and evolutionary consequences of this phenomenon, is of increasing importance given shifting species ranges due to large-scale landscape modification and a changing global climate. Our framework can be used to study a wide range of hybridization dynamics in any terrestrial or aquatic system, including comparisons of distinct environmental conditions or potential management responses.

Overwintering Habitat of American Dipper, <i>Cinclus mexicanus</i>, Observed in an Arctic Groundwater Spring Feeding on Dolly Varden, <i>Salvelinus malma</i>

Perennial groundwater springs along the Alaska and Yukon North Slope provide overwintering habitat for various organisms, including birds and fishes. We observed an American Dipper, Cinclus mexicanus, in the open water of a perennial spring situated in Fish Creek, Yukon, in Ivvavik National Park on 8 March 2018. The observation at Fish Creek was among the most northern documented sightings of an American Dipper during the winter in North America. Moreover, the observation was approximately 650 km farther north than where American Dippers have been documented overwintering in Yukon, making this the most northern Canadian observation documented for this species in any season. Additionally, the American Dipper was photographed feeding on a juvenile Dolly Varden, Salvelinus malma. Although American Dippers are known to feed on small fish, our observation was a novel documentation of a trophic interaction between both species during winter. The open-water habitat in Fish Creek, which is important for both species and has not been previously described, was short (~730 m long), shallow (mean = 20 cm deep), narrow (mean = 2.8 m wide), and cold (mean water temperature = 0.34ºC). While there is little information regarding the ecological interactions of American Dipper overwintering in the Arctic, we note that all observations in the North Slope area during winter occurred in river systems also used by Dolly Varden, which indicates that juvenile Dolly Varden could be an important source of food for American Dipper in winter.

Comparing total mercury concentrations of northern Dolly Varden, Salvelinus malma malma, in two Canadian Arctic rivers 1986–1988 and 2011–2013

Given the importance of anadromous Northern Dolly Varden as a consumption staple for northern residents and the climate- and development-related impacts on total mercury (THg) concentrations, temporal changes in northern Dolly Varden THg concentrations were assessed between historical (1986–1988) and contemporary (2011–2013) periods from two rivers in the north-western Canadian Arctic. In the Rat River, mean THg changed from 79 ± 42 ng/g ww in 1986–1988 to 109 ± 44 ng/g ww in 2011–2013, while in the Firth River, THg changed from 126 ± 45 ng/g ww in 1986–1988 to 178 ± 47 ng/g ww in 2011–2012. Length adjusted values indicated increases in the Firth River were driven by the increased size of fish, but increases in the Rat River were not. After factoring in size, δ13C and δ15N, [THg] was found to be most influenced over time by fish size, but also significantly modified by temporal period and foodweb position. Relationships between log[THg] versus fork-length and log[THg] versus δ13C have remained constant over time in the Rat River, but not in the Firth River, while relationships between log[THg] versus δ15N have remained constant in the Firth River, but not in the Rat River. Changes in the significance and the slope of the relationships relating δ13C and δ15N to log[THg] suggests underlying bioaccumulative processes are temporally variant and will be sensitive to climate-driven changes in the aquatic environments within which fish live and feed.

Growth and reproductive characteristics of rarely observed resident female Dolly Varden (Salvelinus malma malma) in North America

Among North American populations of northern form Dolly Varden (Salvelinus malma malma) exhibiting partial migration, the resident female life history is rarely encountered. Between 2012 and 2016, three sexually mature females confirmed as residents using otolith strontium analysis were captured from three rivers in the western Canadian Arctic (< 1% of residents sampled). Size-at-capture and size-at-age, estimated using otolith back-calculation, were compared to resident males and anadromous females. Fecundity, egg diameter, and gonadosomatic index (GSI) were compared to anadromous female current-year spawners. Resident females (fork length range 220–360 mm) tended to be among the largest-sized residents (two were > 90th percentile). Early size-at-age of resident females either exceeded or were among the largest sizes compared to resident males and pre-smolt anadromous females. Residents had similar fecundity predicted for length and egg size (range 3.5–4.2 mm) compared to anadromous, although GSI (range 13.2–17.4%) was inconsistent among populations. Interestingly, one resident female attained a greater size-at-capture and fecundity than the smallest anadromous current-year spawner. Our results suggest that conditional mating tactics of Dolly Varden can be expressed by both sexes in multiple populations, and increases understanding of Dolly Varden life history diversity and bet-hedging strategies in partially migratory populations.

Foraging behaviour and optimal microhabitat selection in Yukon River Basin nonanadromous Dolly Varden Charr (Salvelinus malma)

AbstractSpecies conservation requires understanding the mechanistic processes of habitat selection and their effects on fitness. Nonetheless, there are few fitness‐based habitat selection models for aquatic organisms. We examined multiple aspects of foraging behaviour of nonanadromous Dolly Varden Charr (Salvelinus malma) in Panguingue Creek, Alaska, USA and applied these data to test a fitness‐based microhabitat selection model. Velocity negatively affected prey capture success, positively affected holding velocity, and had no effect on reactive distance. Dominance was a better predictor of prey capture success than length difference between competitors, but there was no relationship between these variables and holding velocity or reactive distance. We used the velocity–prey capture success relationship to parameterise the microhabitat habitat selection model and compared the predicted optimal holding velocity to the 95% confidence interval (24.9–29.3 cm/s) of holding velocities occupied by Dolly Varden (N = 29) in Panguingue Creek. The prediction of 24.0 cm/s fell just slightly (0.9 cm/s) outside the lower limit of the confidence interval; the model barely failed to predict holding velocity for this species in Panguingue Creek. Although this discrepancy fell within measurement error, model failure also may have been due to influence of high turbulence on fish holding velocities in the creek, low sample sizes imposed by permitting limitations, or field logistical issues. The relationship between velocity and prey capture success is an important aspect of drift feeder habitat selection. Our optimal holding velocity prediction for Dolly Varden should aid in the management and conservation of this species.

The complete mitochondrial genome of the hybrid fish Salvelinus fontinalis (♀) × Salvelinus malma sp. (♂)

The complete mitochondrial genome sequence of the hybrid fish Salvelinus fontinalis (♀) × Salvelinus malma sp. (♂) was sequenced. It was 16,623-nucleotide in length and consisted of 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes, and 2 non-coding regions (L-strand replication origin and control region), showing conserved gene arrangement with most vertebrates. The phylogenetic tree showed the hybrid salmon to be one of the Salvelinus and the relationships of S. fontinalis were closer. The complete mitochondrial genome sequence of S. fontinalis (♀) × S. malma sp. (♂) provided an important dataset for a better understanding of the mitogenomic diversities and evolution in salmon fish as well as novel genetic markers for studying population genetics and species identification.

Plasma insulin-like growth factor-1 is unrelated to female reproductive development in a wild population of Dolly Varden charr Salvelinus malma (Walbaum, 1792)

Insulin-like growth factors (IGFs) are endocrine agents that signal growth in fishes. Because of the interplay between growth and reproduction, endocrine control of the growth axis is thought to have a connection to the reproductive axis. Seasonal patterns and relationships between IGF-1, fish condition, and gonadal development were investigated in a wild population of female Dolly Varden charr Salvelinus malma (Walbaum, 1792) during the summer growing season prior to spawning. Fish were sampled from Florence Lake, Alaska on five sequential sampling trips during April–October 2006. Body and gonad morphometric measurements, and blood plasma samples were obtained for IGF-I quantification. IGF-I increased during summer with fish condition. The gonadosomatic index indicated a pattern of advancing reproductive development in one cohort of fish by August, which indicated impending spawning compared to an immature (non-reproductive) cohort. However, plasma IGF-I levels were not predictive of the sexually maturing cohort. We conclude that IGF-I is not a useful endocrine marker of advancing reproductive state in female Dolly Varden charr but does relate to fish condition during the summer growth period.

The Relationships of the Stone Charr Salvelinus malma kuznetzovi Taranetz, 1933 (Salmoniformes: Salmonidae) of the Kamchatka River Basin Inferred from DNA Sequence Data

The relationships of the stone charr Salvelinus malma kuznetzovi, an endemic taxon to the Kamchatka River basin, were inferred from analysis of the nucleotide sequences of the mitochondrial DNA control region (CR) and cytochrome b (Cytb) and cytochrome oxidase-1 (COI) genes, as well as the nuclear lactate dehydrogenase gene (LDH-C1). Genealogical analysis of mtDNA haplotypes confirmed the phylogenetic closeness of S. m. kuznetzovi, S. albus, and S. m. malma and showed that the above taxa represent the Beringian phylogenetic group of charr. The level of mtDNA divergence between S. m. kuznetzovi, S. albus, and S. m. malma did not exceed the intraspecific variation in Northern Dolly Varden populations. The existence of a cryptic Pleistocene refugium in the Kamchatka River basin has been substantiated; nevertheless, extensive and complex studies of charr of the Beringian group are needed.

Migration tactics affect spawning frequency in an iteroparous salmonid (Salvelinus malma) from the Arctic.

Otolith strontium and multi-year mark-recapture information were used to characterize associations between migration patterns and spawning frequencies in an anadromous Dolly Varden (Salvelinus malma) population (Rat River, Northwest Territories, Canada) that undertakes a long migration between freshwater spawning/overwintering (Fish Creek; a tributary to Rat River) and marine feeding habitats (Beaufort Sea) (~800 km round trip). Reconstructions of lifetime annual migration histories among otolith annuli was matched to information on reproductive status (current-year ‘spawner’ or ‘non-spawner’) that was known in two different, sometimes successive, years for each fish. Two migratory life histories were observed: fish either migrated annually after smoltification or periodically skipped an annual ocean migration to remain in freshwater and spawn. Different spawning frequencies were detected where fish not migrating annually tended to spawn in alternate years (84.6%) more often than those migrating annually (50%). Additionally, annually migrating fish had lower longevity (≤9 years vs. ≤13 years). The evaluation of differences in spawning frequency between sexes, independent of migration tactic, revealed males (84.6%) skipped spawning more often than females (51.2%) suggesting fitness trade-offs between life histories differ between sexes. Further, some fish returned from the sea considerably earlier than the majority of other current-year migrants. Our findings demonstrate intrapopulation diversity in migration behaviour and reproductive frequency.