Kimberly L. Howland

Age determination of a long-lived coregonid from the Canadian North: comparison of otoliths, fin rays and scales in inconnu (Stenodus leucichthys)

We examined otoliths, pelvic fin rays and scales of inconnu to determine precision of age estimates within and between readers, and to compare relative accuracy of estimates from different structures. Our main objective was to determine if readability and estimates from fin rays and scales, which can be non-lethally removed, were similar to those of otoliths, which are generally considered the most reliable ageing structure. Among- and within-reader variation was low for both fin rays and otoliths, but higher for scales. Variation tended to increase with fish length for all structures. Scales were most difficult to read and had age estimates that were significantly lower than the other structures at ages of ten years and greater. Age estimates and readability of fin rays and otoliths were similar.

Microsatellite and mtDNA analysis of lake trout, Salvelinus namaycush, from Great Bear Lake, Northwest Territories: impacts of historical and contemporary evolutionary forces on Arctic ecosystems

Resolving the genetic population structure of species inhabiting pristine, high latitude ecosystems can provide novel insights into the post-glacial, evolutionary processes shaping the distribution of contemporary genetic variation. In this study, we assayed genetic variation in lake trout (Salvelinus namaycush) from Great Bear Lake (GBL), NT and one population outside of this lake (Sandy Lake, NT) at 11 microsatellite loci and the mtDNA control region (d-loop). Overall, population subdivision was low, but significant (global FST θ = 0.025), and pairwise comparisons indicated that significance was heavily influenced by comparisons between GBL localities and Sandy Lake. Our data indicate that there is no obvious genetic structure among the various basins within GBL (global FST = 0.002) despite the large geographic distances between sampling areas. We found evidence of low levels of contemporary gene flow among arms within GBL, but not between Sandy Lake and GBL. Coalescent analyses suggested that some historical gene flow occurred among arms within GBL and between GBL and Sandy Lake. It appears, therefore, that contemporary (ongoing dispersal and gene flow) and historical (historical gene flow and large founding and present-day effective population sizes) factors contribute to the lack of neutral genetic structure in GBL. Overall, our results illustrate the importance of history (e.g., post-glacial colonization) and contemporary dispersal ecology in shaping genetic population structure of Arctic faunas and provide a better understanding of the evolutionary ecology of long-lived salmonids in pristine, interconnected habitats.

Morphological and genetic variation in Cisco ( Coregonus artedi ) and Shortjaw Cisco ( C. zenithicus ): multiple origins of Shortjaw Cisco in inland lakes require a lake-specific conservation approach

The study of cisco diversity in inland lakes of North America has been plagued by taxonomic uncertainty linked to high phenotypic plasticity and an ongoing reliance on morphology to differentiate species. More recently, this uncertainty has hindered the development of conservation plans and status assessments of ciscoes. This study presents the first range-wide comparison of morphological and genetic variation between Cisco (Coregonus artedi) and Shortjaw Cisco (C. zenithicus). Using morphological and genetic data from 17 lakes, three sets of analyses were undertaken to evaluate alternate hypotheses explaining the pattern of cisco phenotypic diversity in inland lakes. Morphotypes (MTs) representing the two taxa were phenotypically distinct (largely reflective of differences in gill raker number and jaw morphology) within lakes but highly variable across lakes. Shortjaw Cisco was only recognizable when compared to sympatric Cisco and some populations were morphologically similar to Cisco from other lakes. Analysis of AFLP data revealed two genetic clusters that conformed to differences in geography (eastern and western groups), rather than hypothesized taxonomic boundaries. Genetic variation strongly suggests that each of these unique sympatric pairs of MTs originated recently and locally, in parallel, from the ancestral Cisco. Phenotypic and genetic distinctiveness between MTs were not related. MTs were sometimes clearly recognizable despite a lack of genetic differentiation, suggesting that the canalization of phenotypic plasticity is unevenly completed across lakes. These results provide evidence that the taxon-based approach is clearly inadequate for the protection of Shortjaw Cisco. In Canada, status assessment should aim to identify lake-specific designatable units (DU). Given the idiosyncratic nature of each instance of Shortjaw Cisco, it is expected that the strength of morphological, biological, ecological and genetic evidence for individual DUs will vary among lakes.

A Comparison of Three Anatomical Structures for Estimating Age in a Slow-Growing Subarctic Population of Lake Whitefish

AbstractIt has been well documented in previous research that otoliths are the preferred hard structure for estimating age in coregonids. However, the slower growth due to short growing seasons experienced by populations in the subarctic region of the boreal zone may alter the utility of alternative nonlethal structures for estimating age. We compared the three most commonly used age estimation structures (otoliths, pectoral fin rays, and scales) for Lake Whitefish Coregonus clupeaformis in a northern (above 50°N) population from Great Slave Lake. This study provides new perspectives regarding the use of different aging structures with fish populations typical of subarctic and arctic environments. Results of ANOVA showed that reader confidence, within-reader precision, and the age estimates themselves were all affected by age structure; reader confidence also varied with age-class. Reader confidence was highest for age estimates from otoliths, followed by pectoral fin rays and then scales. Similarly, with...

eDNA metabarcoding as a new surveillance approach for coastal Arctic biodiversity

Abstract Because significant global changes are currently underway in the Arctic, creating a large‐scale standardized database for Arctic marine biodiversity is particularly pressing. This study evaluates the potential of aquatic environmental DNA (eDNA) metabarcoding to detect Arctic coastal biodiversity changes and characterizes the local spatio‐temporal distribution of eDNA in two locations. We extracted and amplified eDNA using two COI primer pairs from ~80 water samples that were collected across two Canadian Arctic ports, Churchill and Iqaluit, based on optimized sampling and preservation methods for remote regions surveys. Results demonstrate that aquatic eDNA surveys have the potential to document large‐scale Arctic biodiversity change by providing a rapid overview of coastal metazoan biodiversity, detecting nonindigenous species, and allowing sampling in both open water and under the ice cover by local northern‐based communities. We show that DNA sequences of ~50% of known Canadian Arctic species and potential invaders are currently present in public databases. A similar proportion of operational taxonomic units was identified at the species level with eDNA metabarcoding, for a total of 181 species identified at both sites. Despite the cold and well‐mixed coastal environment, species composition was vertically heterogeneous, in part due to river inflow in the estuarine ecosystem, and differed between the water column and tide pools. Thus, COI‐based eDNA metabarcoding may quickly improve large‐scale Arctic biomonitoring using eDNA, but we caution that aquatic eDNA sampling needs to be standardized over space and time to accurately evaluate community structure changes.

Projecting present and future habitat suitability of ship-mediated aquatic invasive species in the Canadian Arctic

A rise in Arctic shipping activity resulting from global warming and resource exploitation is expected to increase the likelihood of aquatic invasive species (AIS) introductions in the region. In this context, the potential threat of future AIS incursions at a Canadian Arctic regional scale was examined. Habitat suitability under current environmental conditions and future climate change scenarios was projected for a subset of eight potential invaders ranked as having a high risk of establishment in the Canadian Arctic based on dispersal pathways/donor regions, biological attributes and invasion history: (1) Amphibalanus improvisus, (2) Botrylloides violaceus, (3) Caprella mutica, (4) Carcinus maenas, (5) Littorina littorea, (6) Membranipora membranacea, (7) Mya arenaria and (8) Paralithodes camtschaticus. Habitat modelling was performed using MaxEnt based on globally known native and non-native occurrence records and environmental ranges for these species. Results showed that under current environmental conditions the habitat is suitable in certain regions of the Canadian Arctic such as the Hudson Complex and Beaufort Sea for L. littorea, M. arenaria and P. camtschaticus. Under a future climate change scenario, all species showed poleward gains in habitat suitability with at least some regions of the Canadian Arctic projected to be suitable for the complete suite of species modelled. The use of these models is helpful in understanding potential future AIS incursions as a result of climate change and shipping at large spatial scales. These approaches can aid in the identification of high risk regions and species to allow for more focused AIS monitoring and research efforts in response to climate change.

Elucidation of ecosystem attributes of two Mackenzie great lakes with trophic network analysis

The Mackenzie Basin in northwestern Canada is a high-latitude region, with one of the largest watersheds in the world. The Mackenzie great lakes, consisting of Great Bear Lake, Great Slave Lake and Lake Athabasca form the large lake complex. The human presence in the area is small in terms of population and industry and thus these ecosystems remain comparatively pristine and show no major changes in the fish communities. Ecopath with Ecosim (EwE), the most important and most used ecosystem trophic network modelling tool to study the ecosystem-level responses to changes, and information available in the scientific literature together with traditional knowledge about Great Slave Lake and Great Bear Lake was used to elucidate the ecosystem attributes. Our models give a cohesive view of these two ecosystems that will allow researchers and decision makers to explore questions regarding the stability of fisheries and future ecological change. The moderate trophic level of fish catch along with the small percentage of primary production required to sustain fisheries in both lakes demonstrated that fisheries were sustainable during the time period modelled. The ecosystem indices and attributes of the comparatively pristine Mackenzie great lakes were compared with those of two Laurentian Great Lakes having similar types of Ecopath ecosystem models. The metrics utilized to assess comparatively the ecosystems maturity, stability and health indicated a decline in ecosystem maturity and stability from pristine Great Bear Lake to transitioning Lake Ontario.

From top to bottom: Do Lake Trout diversify along a depth gradient in Great Bear Lake, NT, Canada?

Depth is usually considered the main driver of Lake Trout intraspecific diversity across lakes in North America. Given that Great Bear Lake is one of the largest and deepest freshwater systems in North America, we predicted that Lake Trout intraspecific diversity to be organized along a depth axis within this system. Thus, we investigated whether a deep-water morph of Lake Trout co-existed with four shallow-water morphs previously described in Great Bear Lake. Morphology, neutral genetic variation, isotopic niches, and life-history traits of Lake Trout across depths (0–150 m) were compared among morphs. Due to the propensity of Lake Trout with high levels of morphological diversity to occupy multiple habitat niches, a novel multivariate grouping method using a suite of composite variables was applied in addition to two other commonly used grouping methods to classify individuals. Depth alone did not explain Lake Trout diversity in Great Bear Lake; a distinct fifth deep-water morph was not found. Rather, Lake Trout diversity followed an ecological continuum, with some evidence for adaptation to local conditions in deep-water habitat. Overall, trout caught from deep-water showed low levels of genetic and phenotypic differentiation from shallow-water trout, and displayed higher lipid content (C:N ratio) and occupied a higher trophic level that suggested an potential increase of piscivory (including cannibalism) than the previously described four morphs. Why phenotypic divergence between shallow- and deep-water Lake Trout was low is unknown, especially when the potential for phenotypic variation should be high in deep and large Great Bear Lake. Given that variation in complexity of freshwater environments has dramatic consequences for divergence, variation in the complexity in Great Bear Lake (i.e., shallow being more complex than deep), may explain the observed dichotomy in the expression of intraspecific phenotypic diversity between shallow- vs. deep-water habitats. The ambiguity surrounding mechanisms driving divergence of Lake Trout in Great Bear Lake should be seen as reflective of the highly variable nature of ecological opportunity and divergent natural selection itself.

Arctic Grayling Movements through a Nature-Like Fishpass in Northern Canada

AbstractUsing a PIT detection system and two in-stream, swim-through antennas, we examined the movements of Arctic Grayling Thymallus arcticus through a low-gradient (<1%), nature-like fishpass that connected two small lakes in the Barrenlands region of northern Canada. We used an ensemble of generalized linear mixed models to evaluate whether passage events (1) were related to fish FL, water depth in the fishpass, and/or temperature in the fishpass; and (2) exhibited any diel patterns. During two seasons, passage events were not related to fish FL or fishpass water temperature; however, the probability of a passage event occurring increased with increases in fishpass depth, which likely served as a proxy for velocity and/or discharge. Most notably, 95% (n = 193/204) of Arctic Grayling passages occurred at night (1800–0559 hours) throughout our study. Although the cause(s) of this diel pattern were not examined directly, we hypothesized that it represented a response to avian predation given the shallow d...