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) 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 remain 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 (<350mm) 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.

Review of the ecosystem approach in Cumberland Sound, Nunavut, Canada

Historically, fisheries have been monitored at the individual stock level, without consideration to connectivity to other species or activities in the ecosystem. The ecosystem approach requires that the stock and fishery be seen in the context of predators, competitors, prey, by-catch impacts, other fisheries and abiotic environmental variables so that management is holistic. In this review, we describe the components of the ecosystem approach applied in the scientific investigation of fisheries in Cumberland Sound, NU. Relative to other Canadian Arctic locales with commercial fisheries operations, the Cumberland Sound area has a greater biodiversity and abundance of fish and marine mammal species These components support active fisheries for Arctic Charr, Greenland Halibut, Beluga Whale as well as Ringed, Bearded and Harp Seal. The species and their fisheries are variable in character, their ecosystem effects and their response to the environment. We describe the species dynamics and their fisheries within an ecosystem context. We briefly note the challenges to developing an overarching model of the system such as the integration of the different life histories of the species, as well as the incorporation of future non-fisheries related disturbances.

Spatio-temporal summer distribution of Cumberland Sound beluga whales (Delphinapterus leucas) in Clearwater Fiord

The Cumberland Sound (Nunavut, Canada) beluga whale (Delphinapterus leucas) population has been designated as threatened and updated biological information about summer distribution is required for a sound recovery plan. Variation in aerial survey counts are speculated to occur due to movement of belugas in and out of the fiord, and there is still uncertainty related to their distribution within key summer habitat. To address these knowledge gaps, non-invasive passive acoustic monitoring (PAM) systems were deployed in August of 2010 and 2011. An automated detector was used to determine presence/absence and quantify calls by recorder site. Results were verified by partial manual analysis of 20% of the files. The detector had a minimum accuracy of 85% for presence/absence and 42% for call quantification. Belugas were detected primarily at the uppermost site of Clearwater Fiord, with detections subsiding with increasing proximity to the fiord entrance. Diel variation in call patterns were quantified at two separate sites in different years, but no correlation was observed between tidal cycles and number of detections. This study indicates that Cumberland Sound beluga may prefer sites at the head of Clearwater Fiord. Further research is required to identify which environmental variables contribute to this observed summer distribution.

The capelin invasion: evidence for a trophic shift in Arctic char populations from the Cumberland Sound region

Climate change is having myriad effects on Arctic marine ecosystems and food webs. Anadromous Arctic Char, Salvelinus alpinus, feed intensively at sea during summer. In Cumberland Sound, NU, there has been a recent increased availability of a forage fish, Capelin. To investigate changes over time in Arctic Char foraging, we assessed Arctic Char trophic niche from 2002 to 2011 using stomach content analysis and stable isotope analysis (δ13C and δ15N) of muscle tissue from two river/lake systems, Isuituq and Kipisa. We also compared population characteristics by calculating Fulton’s condition factor (K) and by fitting von Bertalanffy growth curves with length-at-age data. Results revealed Capelin newly present in the diets of Arctic Char in 2011, describing a shift from a primarily invertebrate-based to a fish-based diet. No trend in δ15N (del 15N) over time suggests the trophic level of Arctic Char has not changed; however, the δ15C (del 15C) for both systems converged in 2011 on a value suggestive of feeding on Capelin. Growth curves and length-at-age analyses suggest that foraging on Capelin may have increased individual growth. Changes in the growth and condition of Arctic Char in this region could have significant economic and cultural implications.

Population dynamics of the threatened Cumberland Sound beluga (Delphinapterus leucas) population

Current scientific evidence indicates the threatened Cumberland Sound beluga (Delphinapterus leucas) 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, Nunavut, Canada, and was harvested commercially from 1860 until 1966. The commercial harvest removed at least 10,000 individuals from the population. Visual and photographic aerial surveys were flown during August 2014 and 2017 and produced beluga whale abundance estimates of 1,151 (CV = 0.214; 95% Confidence Interval [CI] = 760-1,744) and 1,381 (CV = 0.043; CI = 1,270-1,502), respectively. Long-term trends in abundance were examined by fitting a Bayesian surplus-production population model to a time series of abundance estimates (n = 5), flown between 1990 and 2017, taking into account reported subsistence harvests (1960-2017). The model suggests the population is declining. Engaged co-management of the Cumberland Sound beluga population and information on demographic parameters, such as reproductive rates, and age and sex composition of the harvest, are needed to restore the ecological integrity of the Cumberland Sound marine ecosystem.

Bowhead whales use two foraging strategies in response to fine-scale differences in zooplankton vertical distribution

As zooplanktivorous predators, bowhead whales (Balaena mysticetus) must routinely locate patches of prey that are energy-rich enough to meet their metabolic needs. However, little is known about how the quality and quantity of prey might influence their feeding behaviours. We addressed this question using a new approach that included: (1) multi-scale biologging and unmanned aerial system observations of bowhead whales in Cumberland Sound, Nunavut (Canada), and (2) an optical plankton counter (OPC) and net collections to identify and enumerate copepod prey species through the water column. The OPC data revealed two prey layers comprised almost exclusively of lipid-rich calanoid copepods. The deep layer contained fewer, but larger, particles (10% greater overall biomass) than the shallow prey layer. Dive data indicated that the whales conducted long deep Square-shaped dives (80% of dives; averaging depth of 260.4 m) and short shallow Square-shaped dives (16%; averaging depth of 22.5 m) to feed. The whales tended to dive proportionally more to the greater biomass of zooplankton that occurred at depth. Combining behavioural recordings with prey sampling showed a more complex feeding ecology than previously understood, and provides a means to evaluate the energetic balance of individuals under current environmental conditions.

Asynchronous instability of NE ice streams of the Laurentide Ice Sheet recorded in the marine sediments of Labrador Sea during the last glacial cycle

&lt;p&gt;Hughes et al. (1977) hypothesized of a pan-Arctic Ice Sheet that behaved as a single dynamic system during the Last Glacial Maximum. Moreover, the authors suggested a nearly grounded ice shelf in Davis Strait implying that little or no exchange between Baffin Island and the Labrador Sea. Here we present data at 1-cm (&lt;100 years) resolution between ~12 ka and 45 ka that shed light on the discharge from Hudson Strait and Lancaster Sound ice streams of the Late Pleistocene Laurentide Ice Sheet. A reference sediment core at 938 m water depth on the SE Baffin Slope was investigated with new oxygen isotope stratigraphy, X-ray fluorescence geochemistry, and 18 14C-AMS dates and correlated to 14 regional deep-water cores. Detrital carbonate-rich sediment layers H0-H4 were derived principally from Hudson Strait. Shortly after H2 and H3, the shelf-crossing Cumberland Sound ice stream supplied dark brown ice-proximal stratified sediments but no glacigenic debris-flow deposits. The counterparts of H3, H4, and (?)H5 events in the deep Labrador basin are 4&amp;#8211;10 m thick units of thin-bedded carbonate-rich mud turbidites from glacigenic debris flows on the Hudson Strait slope. The behavior of the Hudson Strait ice stream changed through the last glacial cycle. The Hudson Strait ice stream remained at the shelf break in H3-H5 but retreated rapidly across the shelf in H0-H2 and did not deglaciate Hudson Bay. During this time, Cumberland Sound ice twice reached the shelf edge. In H3&amp;#8211;H5, it remained at the shelf break long enough to supply thick turbidites. Minor supply of carbonate-rich sediment from Baffin Bay allows chronologic integration of the Baffin Bay and Labrador Sea detrital carbonate records, which is diachronous with respect to Heinrich events. The asynchrony of the carbonate events implies an open seaway through Davis Strait. Our data suggest that the maximum extent of ice streams in Hudson Strait, Cumberland Sound, and Lancaster Sound was neither synchronous.&lt;/p&gt;

Evidence of killer whale predation on a yearling bowhead whale in Cumberland Sound, Nunavut

Accounts of killer whale (Orcinus orca) predation on marine mammals in the Canadian Arctic are relatively uncommon. Although second-hand reports of killer whale predation events in the Arctic are more common in recent years, these observations are generally poorly documented and the outcome of attacks are often unknown. On 12 August 2016, a floating bowhead whale (Balaena mysticetus) carcass was found off-shore in Cumberland Sound, Nunavut — presumably predated by killer whales that were sighted in the area. Inspection of the carcass revealed injuries consistent with published accounts of killer whale predation on large whales and observations of killer whale predation on bowheads described in Inuit traditional knowledge. The bowhead was male, 6.1 m long in good nutritional condition and estimated between 14 and 16 months old. As a recently weaned yearling, this whale would have been highly vulnerable to killer whale predation. With decreasing summer sea ice making some areas of the Arctic more accessible, the incursion and presence of killer whales in the Arctic is expected to increase. A better understanding of Arctic killer whale predation pressure is needed to predict the potential impact they will have on the eastern Canada–west Greenland bowhead population as well as on other marine mammal prey.