Cory J. D. Matthews

• BSc Hons, MSc, PhD
• Research Scientist at Fisheries and Oceans Canada

Killer whales in the Eastern Canadian Arctic (ECA) prey on narwhal, beluga, bowhead whales and seals, while further south in the north-west Atlantic (NWA), killer whales off the coast of Newfoundland and Labrador prey on both marine mammals and fish. Bulk and amino acid (AA) specific isotopic composition of dentinal collagen in teeth of 13 ECA/NWA...

Eastern Canada-West Greenland (EC-WG) bowhead whales Balaena mysticetus migrate seasonally between northwestern Hudson Bay/Foxe Basin and Gulf of Boothia in summer and Hudson and Davis Straits in winter. Despite recent advances in knowledge of summer diet composition, determining seasonal variation in foraging behaviour of EC-WG bowhead whales rema...

Compound‐specific stable isotope analysis (CSIA) of amino acids (AAs) has been rapidly incorporated in ecological studies to resolve consumer trophic position (TP). Differential 15N fractionation of “trophic” AAs, which undergo trophic 15N enrichment, and “source” AAs, which undergo minimal trophic 15N enrichment and serve as a proxy for primary pr...

The effects of predator intimidation on habitat use and behavior of prey species are rarely quantified for large marine vertebrates over ecologically relevant scales. Using state space movement models followed by a series of step selection functions, we analyzed movement data of concurrently tracked prey, bowhead whales ( Balaena mysticetus ; n = 7...

Significance Predators are widely understood to impact the structure and stability of ecosystems. In the Arctic, summer sea ice is rapidly declining, degrading habitat for Arctic species, such as polar bears and ringed seals, but also providing more access to important predators, such as killer whales. Using data from concurrently tracked predator...

Introduction This study examines 20 years of killer whale (Orcinus orca) sightings (2002–2023) in the eastern Canadian Arctic, drawing from a comprehensive sighting database spanning 1850–2023. Despite inherent biases favoring data collection near communities and coastal areas, spatiotemporal analyses reveal significant shifts in killer whale distr...

Monitoring Arctic marine mammals in response to rapid climate change requires reliable longitudinal data. To obtain such data is challenging, but sequential measurements of stable isotopes (SI) from metabolically inert tissues like dentine allow for chronological reconstruction of SI data that can provide insights into whale life history, behaviour...

Cetacean mortality events in the Arctic often go underreported compared with events in more highly populated regions. Here, we report a mortality event involving the death of 11 bowhead whales around the Gulf of Boothia, Canada. The whales were discovered between October 2020-April 2021. Reports of 11 dead bowhead whales within six months in one ar...

Killer whales (Orcinus orca) occur seasonally in the eastern Canadian Arctic (ECA), where their range expansion associated with declining sea ice have raised questions about the impacts of increasing killer whale predation pressure on Arctic‐endemic prey. We assessed diet and distribution of ECA killer whales using bulk and compound‐specific stable...

1. Killer whales (Orcinus orca) occur seasonally in the eastern Canadian Arctic (ECA), where their range expansion associated with declining sea ice have raised questions about the impacts of increasing killer whale predation pressure on Arctic-endemic prey. 2. We assessed diet and distribution of ECA killer whales using bulk and compound-specific...

The Arctic is the fastest‐warming region on the planet, and the lengthening ice‐free season is opening Arctic waters to sub‐Arctic species such as the killer whale (Orcinus orca). As apex predators, killer whales can cause significant ecosystem‐scale changes. Setting conservation priorities for killer whales and their Arctic prey species requires k...

In the eastern Canadian Arctic, belugas Delphinapterus leucas exhibit genetic and ecological differentiation across their distribution that forms the basis of management stocks for traditional Inuit hunts. Using oxygen and stable carbon isotope ratios in dentine phosphate (δ ¹⁸ O P ) and structural carbonate (δ ¹³ C SC ), respectively, we evaluated...

Ecological applications of compound-specific stable isotope analysis (CSIA) of amino acids (AAs) include 1) tracking carbon pathways in food webs using essential AA (AAESS) δ¹³C values, and 2) estimating consumer trophic position (TP) by comparing relative differences of ‘trophic’ and ‘source’ AA δ¹⁵N values. Despite the significance of these appli...

The Arctic is the fastest-warming region on the planet, and sea ice loss has opened new habitat for sub-Arctic species such as the killer whale ( Orcinus orca ). As apex predators, killer whales can cause significant ecosystem-scale changes, however, we know very little about killer whales in the Arctic. Setting conservation priorities for killer w...

Lipophilic persistent organic pollutants (POPs) tend to biomagnify in food chains, resulting in higher concentrations in species such as killer whales (Orcinus orca) feeding on marine mammals compared to those consuming fish. Advancements in dietary studies include the use of quantitative fatty acid signature analysis (QFASA) and differentiation of...

Temporal variation in food web structure is widespread among highly seasonal environments, such as the Arctic and is driven by changes in resource availability. Variation in resource availability can lead to species differences in diet composition, isotopic niche width, and trophic position (TP) across seasons. Here, we used tissue samples that rep...

Determination of trace element concentrations in continuously growing biological structures such as otoliths, whiskers, and teeth can provide important insight into physiological and ontogenetic processes. We examined concentrations of 11 trace elements (Li, Mg, Mn, Cu, Zn, Se, Rb, Sr, Cs, Ba, Pb) in the annual dentine growth layer groups (GLGs) of...

Serial measurements of hormone concentrations along baleen plates allow for reconstructions of mysticete whale reproductive histories. We assessed gestation and calving interval in bowhead whales (Balaena mysticetus) by measuring progesterone, oestradiol, corticosterone and nitrogen stable isotope ratios (δ¹⁵N) along baleen of 10 females from the e...

Combining mercury and stable isotope data sets of consumers facilitates the quantification of whether contaminant variation in predators is due to diet, habitat use and/or environmental factors. We investigated inter-species variation in total Hg (THg) concentrations, trophic magnification slope between δ 15 N and THg, and relationships of THg with...

As plastic pollution continues to persist at a global level, the Arctic has drawn increased research interest as a possible sink for marine pollutants. Plastic and microplastics are highly durable and can be transported across vast distances. To date, only a handful of studies have directly assessed microplastics in Arctic mammals. In Canada, it is...

Unlabelled: A widespread pattern in vertebrate life-history evolution is for species to evolve towards either fast or slow life histories; however, the underlying causes of this pattern remain unclear. Toothed whales (Odontoceti) are a diverse group with a range of body sizes and life histories, making them an ideal model to investigate potential...

Quantifying the diet composition of apex marine predators such as killer whales (Orcinus orca) is critical to assessing their food web impacts. Yet, with few exceptions, the feeding ecology of these apex predators remains poorly understood. Here, we use our newly validated quantitative fatty acid signature analysis (QFASA) approach on nearly 200 ki...

Climate-driven alterations of the marine environment are most rapid in Arctic and subarctic regions, including Hudson Bay in northern Canada, where declining sea ice, warming surface waters and ocean acidification are occurring at alarming rates. These changes are altering primary production patterns that will ultimately cascade up through the food...

A widespread pattern in vertebrate life-history evolution is for species to evolve towards either fast or slow life histories; however, the possible causes of this pattern are multiple. Toothed whales (Odontoceti) are a particularly speciose group that includes a substantial range of body sizes and life histories and thus represent a model group to...

The recent development of very high-resolution (VHR) satellite imagery allows for unprecedented detection and identification of animals. This report outlines a pilot study in which satellite images of one of the primary terrestrial walrus (Odobenus rosmarus rosmarus) haulout sites in the eastern Canadian Arctic was evaluated as an alternative to co...

Synopsis Male mammals of seasonally reproducing species typically have annual testosterone (T) cycles, with T usually peaking during the breeding season, but occurrence of such cycles in male mysticete whales has been difficult to confirm. Baleen, a keratinized filter-feeding apparatus of mysticetes, incorporates hormones as it grows, such that a s...

Aim Identify hotspots and areas of high species richness for Arctic marine mammals. Location Circumpolar Arctic. Methods A total of 2115 biologging devices were deployed on marine mammals from 13 species in the Arctic from 2005 to 2019. Getis‐Ord Gi* hotspots were calculated based on the number of individuals in grid cells for each species and fo...

While the impact of ecological changes on Arctic marine mammals remains largely unknown, quantifying variability in resource use among conspecifics can serve as an indication of adaptive plasticity and help assess species vulnerability to climate‐induced changes. We measured within‐tooth δ15N and δ13C profiles of narwhals (Monodon monoceros) sample...

Endocrine tools can provide an avenue to better understand mammalian life histories and predict how individuals and populations may respond to environmental stressors; however, few options exist for studying long-term endocrine patterns in individual marine mammals. Here, we (i) determined whether hormones could be measured in teeth from four marin...

Stable isotope analysis (SIA) of sequential dentine growth layer groups can be used to estimate the lifetime diet of individuals and infer major ontogenetic shifts such as the completion of nursing. We used SIA of dentine from narwhal Monodon monoceros embedded canine teeth to investigate ontogenetic dietary patterns, with a focus on nursing durati...

Ecotypes are groups within a species with different ecological adaptations than their conspecifics. Eastern North Pacific (ENP) killer whale (Orcinus orca) ecotypes differ in their diet, behavior, and morphology, but the same is not known for this species in the eastern Canadian Arctic (ECA) and Northwest Atlantic (NWA). Using compound-specific sta...

Killer whales ( Orcinus orca ) are distributed widely in all oceans, although they are most common in coastal waters of temperate and high-latitude regions. The species’ distribution has not been fully described in the northwest Atlantic (NWA), where killer whales move into seasonally ice-free waters of the eastern Canadian Arctic (ECA) and occur y...

Current scientific evidence indicates that the threatened Cumberland Sound beluga whale (Delphinapterus leucas (Pallas, 1776)) population is genetically differentiated and spatially segregated from other beluga whale populations. This population has been hunted for subsistence for centuries by Inuit who now live in the community of Pangnirtung, Nun...

The monodontids—narwhals, Monodon monoceros, and belugas, Delphinapterus leucas—are found in much of the Arctic and in some subarctic areas. They are hunted by indigenous subsistence users. In the past, some populations were substantially reduced by commercial hunting and culling; more recently, some populations have declined due to uncontrolled su...

Nursing and weaning periods are poorly understood in cetaceans due to the difficulty of assessing underwater behaviour in the wild. However, the onset and completion of weaning are critical turning points for individual development and survival, with implications for a species’ life history including reproductive potential. δ¹⁵N and δ¹³C deposited...

The killer whale (Orcinus orca (Linnaeus, 1758)) is a widely distributed marine predator with a broad ecological niche at the species level with evidence of specialization and narrow ecological niches among populations. Their occurrence in Canadian Arctic waters is limited by sea ice and it has been suggested that climate warming, which has caused...

Overview and synthesis of the present state of the Arctic Seas of Canada

Specific case studies in support of the main technical report 3344

Reconstruction of the demographic and evolutionary history of populations assuming a consensus tree‐like relationship can mask more complex scenarios, which are prevalent in nature. An emerging genomic toolset, which has been most comprehensively harnessed in the reconstruction of human evolutionary history, enables molecular ecologists to elucidat...

Reconstruction of the demographic and evolutionary history of populations assuming a consensus tree-like relationship can mask more complex scenarios, which are prevalent in nature. An emerging genomic toolset, which has been most comprehensively harnessed in the reconstruction of human evolutionary history, enables molecular ecologists to elucidat...

Killer whales (Orcinus orca) occur seasonally in the eastern Canadian Arctic during the summer months. Increasing killer whale sightings throughout the region, and incursions into areas where they have not historically been observed, have been linked with declining sea ice, which has raised questions about the potential ecological impacts of a grea...

Male baleen whales have long been suspected to have annual cycles in testosterone, but due to difficulty in collecting endocrine samples, little direct evidence exists to confirm this hypothesis. Potential influences of stress or adrenal stress hormones (cortisol, corticosterone) on male reproduction have also been difficult to study. Baleen has re...

Previous studies have demonstrated that the analysis of biogeochemical tracers along baleen can provide seasonal, annual, and longer term insights into whale movements, habitat use, diet, and ecosystem processes. We measured the mercury (Hg) concentration and stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope compositions along baleen plates of bowhe...

Understanding the diets and trophic relationships of toothed whales is central to understanding their roles in marine ecosystems, and associated conservation issues. Yet this is problematic because direct observation of what free ranging marine mammals eat is difficult. Quantitative 3D textural analysis of tooth microwear (DMTA) offers a new way of...

Spatial variation in marine oxygen isotope ratios (d18O) resulting from differential evaporation rates and precipitation inputs is potentially useful for characterizing marine mammal distributions and tracking movements across d18O gradients. Dentine hydroxyapatite contains carbonate and phosphate that precipitate in oxygen isotopic equilibrium wit...

Killer whales are located by boat, usually after sightings reports are received from local hunters who tell us where to look for them. During all killer whale encounters, we photograph individual whales using digital SLR cameras. Images were collected using three Canon camera bodies (two EOS-ID Mark IV Digital 16.7 megapixel, and one EOS-IDX 18.0 m...

Beluga whales (Delphinapterus leucas) have a protracted nursing period estimated to last from 6-32 months, although current estimates of beluga nursing duration are derived using approaches subject to capture bias. Recent studies have shown stable isotope profiles of dentin growth layer groups (GLGs) in marine mammal teeth serve as a reliable nursi...

Isotopic time series from sequentially sampled growth layer groups (GLGs) in teeth can be combined to build chronologies allowing assessment of isotopic variation in marine ecosystems. Synchronous recording of baseline isotopic variation across dentinal GLGs of species with temporal and spatial overlap in foraging offers a unique opportunity for va...

We report two opportunistic and unusual observations of white-beaked dolphins (Lagenorhynchus albirostris) in the Canadian Arctic that are outside the known range of this species. Sightings occurred off the south-east coast of Baffin Island (Nunavut, Canada) in Frobisher Bay (September 2004) and Cumberland Sound (August 2013). Despite dedicated, mu...

Flooding land for water reservoir creation has many environmental impacts including the production of the greenhouse gases (GHG) carbon dioxide (CO2) and methane (CH4). To assess processes governing GHG emissions from the flooding of terrestrial carbon, three experimental reservoirs were constructed in upland boreal forest areas of differing carbon...

Killer whales (Orcinus orca) occur in the eastern Canadian Arctic during the open-water season, but their seasonal movements in Arctic waters and overall distribution are poorly understood. During August 2009, satellite transmitters were deployed onto two killer whales in Admiralty Inlet, Baffin Island, Canada. A whale tracked for 90days remained i...

The FLooded Uplands Dynamics EXperiment (FLUDEX) was initiated to quantify carbon dioxide (CO2) and methane (CH4) production in boreal reservoirs, and to better understand underlying biogeochemical processes (dissolved inorganic carbon [DIC] production, net primary production [NPP], methanogenesis, and CH4 oxidation) governing CO2 and CH4 productio...

Global atmospheric concentrations of nitrous oxide (N2O), a powerful greenhouse gas, continue to increase. While many sources and sinks have been identified, there is little known about how existing and newly constructed reservoirs, such as those created for hydroelectric production, impact current atmospheric N2O concentrations. We hypothesized th...

The FLooded Uplands Dynamics EXperiment (FLUDEX) was designed to assess the impact of reservoir creation on carbon cycling in boreal forests by (a) determining whether production of the greenhouse gases (GHG) carbon dioxide (CO2) and methane (CH4) in reservoirs is related to the amount of organic carbon (OC) stored in the flooded landscape, (b) exa...

Hydroelectricity is considered a relatively clean source of power, but flooding forests to create reservoirs can generate greenhouse gas emissions and accelerate mercury accumulation. For that reason, a scientific understanding of the environmental effects associated with this practice is important, say R. A. Bodaly, Kenneth G. Beaty, Len H. Hendze...

Three approaches commonly used to quantify diffusive gas exchange across aquatic surfaces were compared in a densely treed, low-wind environment Diffusive surface fluxes of carbon dioxide (CO2) and methane (CH4) from a small boreal reservoir were estimated using (i) surface water concentrations, the thin boundary layer (TBL) equation, and gas trans...