J. Brian Dempson's research while affiliated with Northwest Fisheries Science Center and other places

Publications (130)

Preprint
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Complex traits often exhibit complex underlying genetic architectures resulting from a combination of evolution from standing variation, hard and soft sweeps, and alleles of varying effect size. Increasingly, studies implicate both large-effect loci and polygenic patterns underpinning adaptation, but the extent that common genetic architectures are...
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Gene flow between wild and domestic populations has been repeatedly demonstrated across a diverse range of taxa. Ultimately, the genetic impacts of gene flow from domestic into wild populations depends both on the degree of domestication and the original source of the domesticated population. Atlantic Salmon, Salmo salar, used in North American aqu...
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The escape of domesticated Atlantic salmon Salmo salar from aquaculture facilities represents a continued threat to the genetic and demographic stability of wild salmon stocks. Escaped farm-origin salmon have been shown to hybridize with wild conspecifics, yet the long-term genetic impacts are generally unknown. Theoretically, life history variatio...
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We describe observations of Sea Lamprey (Petromyzon marinus) and Striped Bass (Morone saxatilis) incursions into Labrador, Canada. While P. marinus have been periodically observed in similar latitudes, their numbers have conspicuously increased in estuarine environments in 2020. In contrast, M. saxatilis were not observed from Labrador until 2017 b...
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Using non-lethal tissue biopsies, we investigated somatic energy, lipid composition, and condition in post-spawned Atlantic salmon (kelts, n = 69) returning to sea in the spring and explored contrasts as a function of previous migration- and spawning history, length and sex. Using mark-recapture analysis, we also explored linkages between spawning...
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Arctic charr Salvelinus alpinus are a commercially and culturally valued species for northern Indigenous peoples. Climate shifts could have important implications for charr and those that rely on them, but studies that evaluate responses to ecosystem change and the spatial scales at which they occur are rare. We compare marine-phase habitat use, lo...
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The post-glacial colonization of Gander Lake in Newfoundland, Canada, by Arctic Charr (Salvelinus alpinus) provides the opportunity to study the genomic basis of adaptation to extreme deep-water environments. Colonization of deep-water (> 50 m) habitats often requires extensive adaptation to cope with novel environmental challenges from high hydros...
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Declines in wild Atlantic salmon (Salmo salar) abundance throughout the north Atlantic are primarily attributed to decreases in survival at sea. However, comparing trends in marine survival among populations is challenging as data on both migrating smolts and returning adults are sparse and models are difficult to parameterize due to their varied l...
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A Correction to this paper has been published: https://doi.org/10.1038/s41558-021-01023-8.
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Atlantic salmon (Salmo salar) populations throughout the North Atlantic have declined in recent decades largely due to reduced marine survival, yet our understanding of marine distribution patterns and migratory routes remains limited. Here, we assigned archived individual samples (n = 3891) collected over a half century (1968–2018) throughout the...
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• Warming temperatures resulting from climate change may alter the distribution and abundance of many freshwater fish species, especially those in northern latitudes. Owing to interspecific differences in temperature adaptations and tolerances, warming may lead to changes in the fish community as a result of shifts in the abundance of co‐existing s...
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Despite widespread biodiversity losses, an understanding of how most taxa will respond to future climate change is lacking. Here we integrate genomics and environmental modelling to assess climate change responses in an ecologically and economically important Arctic species. Environmentally associated genomic diversity and machine learning are used...
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Warming water temperatures, combined with increased mortality following catch and release, could have synergistic consequences if rivers remain open to catch and release at high water temperatures, and catchability of fish remains similar across water temperatures. Here archived data for Atlantic salmon, Salmo salar L., were used to (a) quantify th...
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Human activities have the potential to accelerate population-level decline by contributing to climate warming and decreasing the capacity of species to survive warming temperatures. Here we build a predictive model to test interactions between river warming and catch-and-release mortality in recreational fisheries for Atlantic salmon (Salmo salar L...
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The resiliency of populations and species to environmental change is dependent on the maintenance of genetic diversity, and as such quantifying diversity is central to combatting ongoing wide spread reductions in biodiversity. With the advent of next‐generation sequencing, several methods now exist for resolving fine‐scale population structure, but...
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Combining detailed temporal and spatial catch data, including catch per unit effort, with a high-resolution microsatellite genetic baseline facilitated the development of stock-specific coastal migration models for the four largest Atlantic salmon (Salmo salar) populations, Målselv, Alta, Tana and Kola rivers, contributing to the Barents Sea mixed-...
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Acoustic and archival telemetry were used to study the marine movements of 115 anadromous Arctic Char, Salvelinus alpinus, at two sites in southern Labrador, Canada, in relation to daily variation in temperature and depth use, body size, and their effects on marine activity patterns. Although evidence varied between locations, Arctic Char generally...
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Migratory behaviour may vary according to the life history and demographic attributes of fish and lead to the spatial segregation of distinct population segments during the non-breeding season. In adult Atlantic salmon, spawning history differences are associated with intra-population variation in marine movements, but the degree of connectivity in...
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Anadromous Arctic charr, Salvelinus alpinus, migrate back to freshwater in late summer to spawn and/or overwinter. While seasonal movement patterns during the freshwater residency period are generally understood, specifics of the short temporal activity patterns remain poorly characterized. This study used temperature and accelerometer sensing tele...
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Owing to the iteroparous nature of Atlantic salmon, a seaward migrating cohort may consist of juveniles and adults that differ in size, maturity, experience, and in the motivation and consequences of migratory movements. Few studies have investigated the role of ontogeny in shaping intra-population variability in movement patterns among Atlantic sa...
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The marine portion of Atlantic salmon Salmo salar L. life history is not well understood, with many populations exhibiting declines in survival and growth linked to changes in the food web. Atlantic salmon of North American origin feed along the coast of West Greenland from August to November and are exposed to a variety of different ecosystems and...
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ABSTRACT: Genetic interactions (i.e. hybridization) between wild and escaped Atlantic salmon Salmo salar from aquaculture operations have been widely documented, yet the ability to incorporate predictions of risk into aquaculture siting advice has been limited. Here we demonstrate a model-based approach to assessing these potential genetic interact...
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Domestication is rife with episodes of interbreeding between cultured and wild populations, potentially challenging adaptive variation in the wild. In Atlantic salmon, Salmo salar, the number of domesticated individuals far exceeds wild individuals, and escape events occur regularly, yet evidence of the magnitude and geographic scale of interbreedi...
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Anadromous Arctic char (Salvelinus alpinus) migrate back to fresh water in late summer to spawn and (or) overwinter. Upon freshwater entry, feeding is reduced or absent, and movement activity is restricted. While the physiological responses to low temperatures (e.g., growth, metabolism) are understood, specifics of the use of thermal habitat for ov...
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The escape of Atlantic salmon (Salmo salar) from aquaculture facilities can result in both negative genetic and ecological interactions with wild populations, yet the ability to predict the associated risk to wild populations has remained elusive. Here we assess the potential of a spatiotemporal database of aquaculture facility locations, productio...
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Anadromous Arctic charr, Salvelinus alpinus, feed in the marine environment for several months during the summer and migrate back to fresh water in late summer to spawn and/or overwinter. While overwintering, anadromous Arctic charr are generally believed to reduce or cease feeding, and they are poorly described in their winter movement activity. T...
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Investigations on the marine feeding of Atlantic salmon (Salmo salar L.) in the Northwest Atlantic are limited compared with the Northeast Atlantic. Climate-induced changes to food webs in Atlantic salmon feeding areas have been noted, alongside increased mortality despite a cessation of most marine fisheries. As forage efficiency may be hampering...
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Body-element content was measured for three life stages of wild Atlantic salmon Salmo salar from three distinct Newfoundland populations as individuals crossed between freshwater and marine ecosystems. Life stage explained most of the variation in observed body-element concentration whereas river of capture explained very little variation. Element...
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The West Greenland Atlantic Salmon (Salmo salar) fishery represents the largest remaining mixed-stock fishery for Atlantic Salmon in the Northwest Atlantic and targets multi-sea-winter (MSW) salmon from throughout North America and Europe. We evaluated stock composition of salmon harvested in the waters off West Greenland (n = 5684 individuals) usi...
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Interceptory fisheries represent an ongoing threat to migratory fish stocks particularly when managed in the absence of stock specific catch and exploitation information. Atlantic salmon from the southern portion of the North American range may be subject to exploitation in the commercial and recreational salmon fisheries occurring in the French te...
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Nutrient transport across ecosystem boundaries by migratory animals can regulate trophic and biogeochemical dynamics of recipient ecosystems. The magnitude and direction of net nutrient flow between ecosystems is modulated by life history, abundance and biomass, individual behavior, and body element composition of migrating individuals. We tested c...
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The use of fish scales in stable isotope ecology studies is becoming increasingly prevalent, especially for rare species where non-lethal sampling methods are preferable. In studies of Atlantic salmon (Salmo salar L.) ecology, scale samples have been used to assess trophic interactions and migrations. The use of scales is complicated by their archi...
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Otolith-derived estimates of mean marine temperatures used by West Greenland 1SW Atlantic salmon (Salmo salar) of North American origin were determined for fish collected in 2009 and 2010. Otolith material corresponding to the second summer at sea was subsampled, via micro-milling, and analysed by mass spectrometry to produce stable oxygen isotope...
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Svenning, M-A., Kanstad-Hanssen, Ø., Lamberg, A., Strand, R., Dempson, J.B. & Fauchald, P. 2015. Incidence and timing of escaped farmed Atlantic salmon (Salmo salar) in Norwegian rivers; inferred from video surveillance, fish trap monitoring and snorkeling – NINA report 1104. 53 pp. Incidence of escaped farmed salmon The average incidence of escape...
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Fisheries targeting mixtures of populations risk the overutilization of minor stock constituents unless harvests are monitored and managed. We evaluated stock composition and exploitation of Atlantic salmon (Salmo salar) in a subsistence fishery in coastal Labrador, Canada, using genetic mixture analysis and individual assignment with a microsatell...
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Countergradient variation (CGV) is defined as genetic variation that counteracts the negative influences of the physical environment, minimising phenotypic variability along an environmental gradient. CGV is thought to have relevance in predicting the response of organisms to climate variability and change. To test the hypothesis that growth rate i...
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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 char...
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The identification of landscape or climatic correlates of genetic connectivity can reveal the processes that regulate spatial diversity and inform the management and conservation of exploited or endangered species. Increasingly, the role of local adaptation in regulating spatial structure is gaining recognition, though disentangling its influence f...
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Anadromous and non-anadromous Arctic charr (Salvelinus alpinus) from multiple sample sites in Labrador, Canada were used to investigate possible differences in total mercury concentration ([THg]) between 1977-78 and 2007-09. The mean [THg] of anadromous Arctic charr was 0.03μg/g wet weight (ww) in 1977-78 and 0.04μg/g ww in 2007-09, while mean conc...
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In an effort to address the decline in abundance of Atlantic salmon, Salmo salar L., in insular Newfoundland rivers, resource managers introduced a River Classification System (RCS) in 1999 to assist in the management and conservation of the resource. The RCS set daily and seasonal bag limits in the recreational fishery on a river by river basis. A...
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Temporal diet changes can be detected by comparing δ13C and δ15N values between tissues with different isotopic turnover times. However, other factors contribute to disparities in δ13C and δ15N signatures between tissues and could confound the interpretation of stable isotope data. We examined the effects of ecological factors on differences in mus...
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Migrations between different habitats are key events in the lives of many organisms. Such movements involve annually recurring travel over long distances usually triggered by seasonal changes in the environment. Often, the migration is associated with travel to or from reproduction areas to regions of growth. Young anadromous Atlantic salmon (Salmo...
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Reddin, D. G., Hansen, L. P., Bakkestuen, V., Russell, I., White, J., Potter, E. C. E., Dempson, J. B., Sheehan, T. F., Ó Maoiléidigh, N., Smith, G. W., Isaksson, A., Jacobsen, J. A., Fowler, M., Mork, K. A., and Amiro, P. 2013. Distribution and biological characteristics of Atlantic salmon (Salmo salar) at Greenland based on the analysis of histor...
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Previous research has documented that total mercury concentrations ([THg]) are lower in anadromous Arctic charr than in non-anadromous conspecifics, but the two life-history forms have rarely been studied together. Here, data from nine pairs of closely-located anadromous and non-anadromous Arctic charr populations were used to explore the impact of...
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Charrs, fishes of the genus Salvelinus (Salmonidae), comprise about 7–20+ species important in the ecosystems and fisheries of Arctic and sub-Arctic waters. Charrs vary by life-history type (anadromous vs. lacustrine), are noted for variability in morphology, colouration and feeding and habitat use across their range, and occur from temperate regio...
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Patterns of total Hg (THg) and methyl Hg (MeHg) biomagnification were investigated in six pairs of co-located lacustrine and marine food webs supporting a common predator, Arctic charr. Mercury biomagnification rates (the slope of log Hg concentration versus δ(15)N-inferred trophic level) did not differ significantly between the two feeding habitat...
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The influence of different climate variables on the first four years of otolith growth in Salangen Arctic charr, Salvelinus alpinus, was studied over the period 1939–2005. Salangen is a coastal, low altitude, subarctic lake system located in northern Norway. Climate data, including water temperature, air temperature, ice-cover and precipitation, we...
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Abstract Patterns of change in angler participation and demographics were examined for the recreational Atlantic salmon, Salmo salar L., fishery in Newfoundland and Labrador, Canada. An analysis of a licence stub return system, 1994–2010, showed a significant decline in resident angler participation, but this was not consistent across all regions o...
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Dixon, H. J., Power, M., Dempson, J. B., Sheehan, T. F., and Chaput, G. 2012. Characterizing the trophic position shift in Atlantic salmon (Salmo salar) from freshwater to marine life-cycle phases using stable isotopes. – ICES Journal of Marine Science, 69: 1646–1655. Marine survival and recruitment of Atlantic salmon (Salmo salar) are commonly tho...
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Abstract – Stable oxygen isotopes (δ18O) derived from otoliths were used to estimate mean annual water temperatures experienced by individual Svalbard Arctic charr, Salvelinus alpinus (L.), during their first four growth seasons. The analysed Arctic charr experienced a high variety of temperatures, indicating the use of different thermal habitats....
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Atlantic salmon Salmo salar smolts (n = 181) from two rivers were surgically implanted with acoustic transmitters and released to determine migration route, residency time and survival in a 50 km long estuarine fjord located on the south coast of Newfoundland, Canada. Data obtained from automated receivers placed throughout the Bay d'Espoir fjord i...
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Atlantic salmon (Salmo salar) management in eastern Canada is based on ensuring that there is sufficient spawning escapement to meet an egg deposition target that maximizes the production of smolts. Using available egg deposition to smolt production data, we show that the present strategy of basing spawning targets on the presence-absence of lacust...
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Information on adult and larval sea lamprey, Petromyzon marinus, from Terra Nova River, Newfoundland, provides the first documented occurrence of a spawning population of lamprey from this province. Sea lamprey captured on the spawning grounds in mid-July 1989 ranged in length from 530 to 687 mm. Larvae collected in 1989 and 1990 ranged in length f...
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We present a simple model of salmonid life history, and calculate the sensitivity of its outputs to its parameters. Theoretical calculations are preferred to computer simulations. There are some parameters for which the sign of the sensitivity is independent of the actual parameter values. In an uncertain world, management actions aimed at altering...
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Mean ambient water temperatures experienced by individual young-of-the-year (YOY) Arctic charr, Salvelinus alpinus (L.), from a Svalbard lake were estimated using measurements of oxygen stable isotopes (δ18O) derived from fish otoliths. Otolith-derived water temperatures differed significantly from temperatures recorded at the outlet river of the D...
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Eighteen genera of metazoan parasites (Monogenea, 1; Digenea, 7; Cestoda, 4; Nematoda, 4; Acanthocephala, 1; Copepoda, 1) were collected from 172 landlocked and anadromous Arctic charr (Salvelinus alpinus Linnaeus) in northern Labrador. Four species (Lecithaster gibbosus, Diphyllobothrium dendriticum, Diphyllobothrium ditremum, and Salmincola carpi...
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The voluminous literature on the freshwater and diadromous fishes of Labrador is summarized in distributional maps. A total of 25 obligate freshwater spawning and one catadromous species has been reported. Fishes from Atlantic and Mississippi refugia probably invaded the region from the Great Lakes basin primarily via glacial Lake Barlow-Ojibway, c...
Chapter
Atlantic salmon, Salmo salar , are opportunistic feeders, utilising a wide variety of available prey throughout all life stages while feeding at sea. It is during this time that they build up the bulk of their final body size with many fish increasing in weight 1000 - fold or more. Their main prey are different species of fish and fish larvae and p...
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A species-specific fractionation equation for Arctic charr (Salvelinus alpinus (L.)) was developed experimentally for use in ecological studies of temperature-driven phenologies for the species. Juvenile Arctic charr were reared in controlled conditions at different temperatures (2–14°C), with three replicates of each temperature. Otoliths from the...
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Several studies have revealed relationships between annual size-at-catch and various climatic factors for anadromous Arctic charr (Salvelinus alpinus) captured as part of the commercial fishery at Nain, Labrador (Nunatsiavut), Canada. Here, changes in growth patterns are examined among cohorts subject to differing lifetime temperature regimes, ther...