Early Summer Near-Shore Fish Assemblage And

JGLR-00897; No. of pages: 11; 4C: 6, 7 Journal of Great Lakes Research xxx (2015) xxx–xxx

Contents lists available at ScienceDirect

Journal of Great Lakes Research

journal homepage: www.elsevier.com/locate/jglr

Early summer near-shore ﬁsh assemblage and environmental correlates in an Arctic estuary

Marie-Julie Roux a,1,LoisA.Harwoodb,⁎,XinhuaZhuc,2, Paul Sparling d,3 a National Institute of Water and Atmospheric Research, 301 Evans Bay Parade, Greta Point, Wellington 6021, New Zealand b Fisheries and Oceans Canada, 301-5204 50th Avenue, Yellowknife, NT X1A 1E2, Canada c Fisheries and Oceans Canada, Freshwater Institute, 501 University Crescent, Winnipeg, Manitoba R3T 2N6, Canada d White Mountain Environmental Consulting, PO Box 10140, Whitehorse, YT Y1A 7A1, Canada article info abstract

Article history: Knowledge of reference conditions and species–environment associations is required to ascertain ongoing aquat- Received 20 October 2014 ic biodiversity changes in Arctic regions. The objective of this study was to establish a baseline of fish community Accepted 20 March 2015 structure (species composition, incidence and relative abundance) in relation to salinity, pH and temperature Available online xxxx gradients in an Arctic estuary, the Husky Lakes, Canada. Sampling involved an early-summer, standardized, experimental netting survey around the entire perimeter of all estuary basins and peninsulas. Detrended canonical Communicated by Pete Cott correspondence analysis (DCCA) was used to evaluate species–environment associations. The ecosystem sustains fi Index words: an abundant and diverse sh community, characterized by co-dominance of coregonids and a marine schooling Arctic aquatic ecosystem fish, Clupea pallasii, and high abundance of freshwater/freshwater-amphidromous species in the innermost ba- Fish assemblage sins. Highest richness and total abundance were related to mixing conditions, warmest temperatures, connectiv- Thermohaline properties ity to nearby ecosystems, and diversity in species life histories. Salinity determined spatial patterns of fish species Coregonids abundance and distribution. The incidence of freshwater fish was limited by the availability of low salinity habitat Lake trout and potential community interactions. These fish, particularly Salvelinus namaycush and Thymallus arcticus, are fi Paci cherring considered as the most vulnerable to changes in freshwater habitat availability. The fish assemblage reflects environmental information from surrounding fluvial, freshwater, coastal marine and catchment ecosystems, and is thus a prime candidate for monitoring environmental change in the region. The results provide a benchmark against which future studies of fish communities can be compared to evaluate potential effects of climate change and anthropogenic development on fish populations from Husky Lakes and similar Arctic aquatic ecosystems. Crown Copyright © 2015 Published by Elsevier B.V. on behalf of International Association for Great Lakes Re- search. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Introduction that link species abundance and distribution with environmental drivers is required to better anticipate and evaluate changes in the Canada's Arctic aquatic environments are expected to undergo biological integrity of northern aquatic environments. important biodiversity transformation over the next few years, yet Fish are mobile consumers that play a significant role in the func- remain poorly sampled and under-described (Archambault et al., tioning of Arctic aquatic ecosystems (Reist et al., 2006). The Arctic 2010; ACIA, Arctic Climate Impact Assessment, 2013). Changing climate guild comprises fish species with limited distribution and/or narrow and a growing incidence of anthropogenic activities are impacting physiological ranges that are particularly sensitive to changing environ- aquatic habitat structure and productivity and may trigger changes in mental conditions (Roessig et al., 2004; Reist et al., 2006; Pörtner and the occurrence, abundance and distribution of aquatic organisms Peck, 2010). On the other hand, several Arctic fishes exhibit complex (Roessig et al., 2004; Reist et al., 2006; Wrona et al., 2006; Pörtner and life histories enabling them to occupy a variety of habitats and take Peck, 2010). Information on reference conditions and the mechanisms advantage of patchy and highly seasonal resources (Craig, 1984; Power, 1997; Tallman et al., 2002; Reshetnikov, 2004; Kissinger et al., ⁎ Corresponding author. Tel.: +1 867 669 4916. 2015). Estuarine fish communities integrate environmental information E-mail addresses: [email protected] (M.-J. Roux), from marine, freshwater and terrestrial (catchment) environments [email protected] (L.A. Harwood), [email protected] (X. Zhu), (Khlebovich, 1997; Whitfield and Harrison, 2008), and are thus excel- [email protected] (P. Sparling). lent candidates for monitoring environmental change (Whitfield and 1 Tel.: +64 4 386 0816. 2 Tel.: +1 204 983 7795. Elliot, 2002). Compared to lacustrine or marine ecosystems, estuaries 3 Tel.: +1 867 399 7019. are likely to exhibit earlier responses to changes such as loss of native http://dx.doi.org/10.1016/j.jglr.2015.04.005 0380-1330/Crown Copyright © 2015 Published by Elsevier B.V. on behalf of International Association for Great Lakes Research. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Please cite this article as: Roux, M.-J., et al., Early summer near-shore fish assemblage and environmental correlates in an Arctic estuary, J. Great Lakes Res. (2015), http://dx.doi.org/10.1016/j.jglr.2015.04.005 2 M.-J. Roux et al. / Journal of Great Lakes Research xxx (2015) xxx–xxx species, proliferation of exotic species and episodic or discrete extreme 133°30′W and 130°55′W longitude (Fig. 1). The estuary consists of weather events (Roessig et al., 2004; Gillson, 2011; Nyitrai et al., 2012). five interconnected basins, two sets of narrow channels (the ‘outer Environmental variables are key drivers of fish community structure fingers’ and the ‘inner fingers’), and a small inlet (‘Kugaluk Channel’) and functioning in estuaries (Whitfield and Elliot, 2002). Salinity near the mouth (Fig. 1). A shallow sill near Thumb Island separates is often the main environmental parameter determining spatial organiza- the Husky Lakes from Liverpool Bay (Carmack and Macdonald, 2008). tion in estuarine fish assemblages (Whitfield, 1999; Jaureguizar et al., From Thumb Island, the Husky Lakes extend approximately 130 km 2004; Eick and Thiel, 2014). Water temperature, pH, turbidity and inland and cover an area of 1933 km2. On average, the estuary is oxygen concentrations, are other key environmental variables that delim- ice-covered eight months of the year, with ice thickness up to approxi- it the range of fish species through physiological demands and thus affect mately 2 m (Macdonald et al., 1999). The system is supported by a the structure of fish communities (Wetzel, 1983; Whitfield, 1999; small, truly Arctic drainage basin that is underlain by permafrost and Whitfield and Elliot, 2002; Barnes and Mann, 2009; Eick and Thiel, becomes entirely frozen in the winter (Macdonald et al., 1999). The 2014). Water properties are one of two interrelated components of fish estuary is subject to semidiurnal tides of small amplitude (b0.5 m), habitat, along with physical variables such as ecosystem size, and has a complex bathymetry characterized by alternating shallows bathymetry, and shoreline and catchment characteristics. Physical and deep pools/channels (Roux et al., 2014). These physical features habitat structure has a direct influence on water property gradients promote water mixing throughout the system, including saltwater (e.g., by determining horizontal and vertical mixing processes). Water intrusion more than 100 km inland (Carmack and Macdonald, 2008; properties are also readily influenced by changes in ambient conditions Roux et al., 2014). or disturbance. Climate changes that affect permafrost and erosion, freshwater runoff, and ice and snow accumulation (Prowse et al., 2006), are Data collection likely to have significant impacts on water properties and fish assemblages in Arctic aquatic systems. Changes in salinity and temperature gra- Data on the near-shore fish community and water properties were dients can affect habitat availability and feeding opportunities for fish in collected during an experimental netting survey conducted shortly estuaries, as well as the timing and success of key life processes such as after ice breakup between late-June and mid- to late-July, over four con- recruitment, growth and migrations (Roessig et al., 2004; Reist et al., secutive years (2001–2004). Each year, the sampling period corres- 2006; Gillson, 2011; Morrongiello et al., 2014). ponded to the period of 24-h daylight. Due to the vast extent of the There is limited information on estuarine fish assemblages and their system and logistic constraints, annual sampling effort generally relationships to water property gradients in northern environments. focused on a particular section of the estuary (see Roux et al., 2014 for The available studies are generally descriptive in nature, often based details). Sampling was not replicated within or among years at any site. on incomplete sets of biological and/or environmental data, and lack A total of 585 experimental gill nets were set in Husky Lakes and detailed quantitative analyses of fish populations and communities Kugaluk Channel (Fig. 2). Multi-mesh gill nets that were 54.9 m in (e.g., Alexander, 1975; Morin et al., 1980; Craig, 1984; Griffiths et al., length and 1.8 m or 3.7 m in height were used. Each net consisted of 1998; Jarvela and Thorsteinson, 1999; Novikov et al., 2000). three 18.3 m panels of 76-mm (3 in.), 38-mm (1.5 in.) and 64-mm This paper investigates the near-shore fish community of Husky Lakes, (2.5 in.) knot-to-knot stretched monofilament mesh. Nets were anchored an Arctic estuary with historical and present-day economic and cultural close to shore in approximately 0.5 m of water and set perpendicular importance to the Inuvialuit of Canada's Western Arctic (Cobb et al., to the shore at intervals of approximately 1 km along the perimeter 2008; ILA, Inuvialuit Land Administration, 2011). Aspects of the ecosys- of all basins and fingers/channel areas. The end panels of 76-mm or tem that were previously described include primary production and the 64-mm were alternated at the shore end. Soaking time was approxi- zooplankton community (Evans and Grainger, 1980; Grainger and mately 60 min per set. Location, maximum depth and catch (counts of Evans, 1982) as well as catchment hydrology, ice cover dynamics and fish, by species) and effort (total fishing time, in minutes) information physical oceanography (Gushue et al., 1996; Macdonald et al., 1999; was recorded for all sets. Fish were identified to species and enumerated Carmack and Macdonald, 2008). A number of fisheries-related studies fo- prior to release. Net depth was recorded at all sites using a Garmin cusing mainly on Liverpool Bay (adjacent to Husky Lakes) were conduct- GPSMAP 168 Sounder. Surface water temperature, salinity and pH mea- ed in the 1980s and early 1990s (e.g., Shields, 1988; Bond and Erickson, surements were taken at 196 random locations in Husky Lakes and at 1992, 1993). some of the netting sites (n = 173 for salinity/pH; n =369fortemper- A survey of the entire ecosystem, including data collection on physical ature) in all years using a Horiba U-10 water quality profiler. habitat structure, water properties, zooplankton, and sampling of the near-shore fish community, was conducted in early summer (immediately after ice break-up) over four consecutive years (2001–2004). This provided Data analyses the first comprehensive dataset on both the fish populations and habitat components of Husky Lakes. Information from all study components is Environmental variables summarized in Roux et al. (2014).Inthispaper,fish abundance and Surface water properties (salinity, pH, and temperature), net setting water properties (salinity, temperature and pH) data are used to character- depth and distance from the mouth were the environmental variables ize fish community structure in terms of species composition, richness, in- which comprised our basic dataset for Husky Lakes. Distance from cidence and life histories and to identify patterns of fish species abundance mouth was determined for all net sets as distance from Thumb Island and distribution in relation to salinity, temperature and pH gradients. Our (69°27′N, 130°53′W, Fig. 1). objective is to establish a baseline of fish community structure in terms of Salinity, temperature and pH data were interpolated to the entire species composition in relation to abiotic factors, to inform future assess- Husky Lakes surface using inverse distance weighted averaging (cell ments of ongoing climate and anthropogenic forcing on fish populations size = 100 m, distance exponent (power) = 2) in ArcGIS. Interpolated in Husky Lakes and similar Arctic aquatic environments. data were used to assign temperature, pH and salinity measurements to individual net sets. Comparisons between observed and interpolated Materials and methods data produced average differences (mean ± sd) of 0.2 ± 1.7 °C for temperature; 0.01 ± 0.08 for pH; and 0.04 ± 0.41 ppt for salinity. Study area Multivariate hierarchical clustering (complete linkage) was used to group netting sites based on similarities in environmental vari- The Husky Lakes are located in the Arctic coastal tundra eco- ables. Cluster definition and validity were determined based on pseudo region between approximately 68°40′Nand69°70′N latitude, and T-square and Duda–Hart indices (Duda and Hart, 1973).

Fig. 1. Geographical location of the Husky Lakes estuary in the coastal Beaufort Sea Region, Canada, including location of the Inuvialuit communities of Tuktoyaktuk and Inuvik, important catchment lakes and river ecosystems, Thumb Island, Kugaluk Channel and the Outer ﬁngers and Inner ﬁngers areas.

Fish community each species (i). Catch proportion is the percentage of species i catch

Fish community composition and relationships to environmental (Catchi)overtotalcatch(CatchT): variables were assessed using presence only data (i.e., nets with positive catch of any species). Catch proportion (%Catch), frequency of occurrence Catchi %Catchi ¼ 100 ð1Þ (%Freq) and an index of relative importance (IRI) were determined for CatchT

Fig. 2. Location of experimental netting sites (n = 523) in Husky Lakes, as distinguished into three areas (‘A’ (empty black circles); ‘B’ (ﬁlled grey circles) and ‘C’ (ﬁlled black circles)), based on similarities in environmental variables determined from hierarchical cluster analysis.

Frequency of occurrence (Freqi) is the number of experimental nets and warmer (N10 °C) waters (Table 1). Area B corresponds to the in which species i was caught, expressed as a percentage relative to the middle section of the estuary characterized by intermediate salinity total number of nets (FreqT). (6.7–13.0 ppt), temperature (6.0–14.5 °C) and pH (7.1–8.8). Area C extends from Kugaluk Channel near the mouth to the outer fingers % ¼ Freqi ð Þ and beyond. This area had a higher mean salinity (12.5 ppt) and lower Freqi 100 2 FreqT mean temperature (8.1 °C) and pH (7.3) and was characterized by a broader range of salinity, temperature and pH values, suggestive of The index of relative importance (IRI) is the product of species i catch important water mixing phenomena. Net depth varied 0.5–27 m and proportion (%Catchi) and frequency occurrence (%Freqi) over the sum averaged 5.2 m in all areas. product of all species catch proportion (%Catchi) and frequency occurrence (%Freqi), expressed as a percentage (Zhu et al., 2008): Fish community metrics % % X Catchi Freqi N %IRIi ¼ 100 ð3Þ In total, 523 of the 585 test nets resulted in positive ( 0) catch and %Catch %Freq i¼1 i i were retained for analyses. A total of 5949 fish specimens belonging to 8 families and 19 species were caught during the study period %IRIi was used to rank species incidence according to the following (Table 2). A species group (cod species) was created due to uncertainty thresholds: in species identification. The cod group included at least three species (saffron cod Eleginus gracilis, Greenland cod Gadus ogac and a few %IRI Incidence ‘unidentified’ specimens, presumably Arctic cod Boreogadus saida). ≥20 Dominant Richness ranged from 1 to 8 in experimental nets (mean 2.2 ± 1.3 5–19 Common over the entire survey). Salmonidae was the most diverse and abundant 0.1–4 Occasional family with 8 species together accounting for more than half (58%) b0.1 Rare of the total catch. The genus Coregonus was dominant, including lake whitefish Coregonus clupeaformis,leastciscoCoregonus sardinella, Fish species were classified into one of four life history categories: Arctic cisco Coregonus autumnalis and broad whitefish Coregonus 1) marine (entire life cycle completed in saltwater); 2) freshwater (entire nasus.Lakewhitefish and least cisco were the most frequently encoun- life cycle completed in freshwater); 3) freshwater-amphidromous (life tered species in the estuary, occurring in 48% and 43% of experimental cycle in freshwater with facultative, localized movements into saltwa- nets, respectively. Pacific herring Clupea pallasii dominated the catch ter); and 4) anadromous (life cycle involving reproduction in freshwater in numbers (25%) and in terms of relative abundance (CPUE 2.28). and annual (often long distance) feeding migrations into saltwater). Life Lake whitefish, least cisco and Pacific herring were ranked as domi- history types were assigned to individual species by reviewing the rele- nant species, among which lake whitefish had the highest incidence vant information in the scientific literature. Richness was defined as the (%IRI 35.6). Common species were Arctic cisco and the starry flounder total number of species. Platichthys stellatus which together explained 19% and 16% of total Catch per unit effort (CPUE) was used as an index of fish relative abun- catch and IRI, respectively. Six species were ranked as having occasional dance. CPUE was estimated for each species as the total number of fish incidence, including lake trout Salvelinus namaycush (%IRI 1.1), the cod caught per 100 m2 of experimental net, per hour. Detrended canonical group (%IRI 0.58), broad whitefish C. nasus (%IRI 0.53), four-horn sculpin correspondence analysis (DCCA) was used to investigate associations be- Myoxocephalus quadricornis (%IRI 0.40), northern pike Esox lucius (%IRI tween fish relative abundance and environmental variables (ter Braak, 0.31) and another Pleuronectidae, the Arctic Flounder Pleuronectes 1986, 1994; ter Braak and Verdonschot, 1995). DCCA is a multivariate di- glacialis, which occurred in relative high numbers (CPUE 0.29) in less rect ordination technique that extracts the linear combination of environ- than 10% of the nets. Lake trout had the highest frequency of occurrence mental variables to maximize dispersion in species abundance (restricted in test nets (%Freq 16) among occasional species. Rare species included to be a linear combination of the supplied environmental variables). It is a (by decreasing order of %IRI), inconnu Stenodus leucichthys,Arcticgray- powerful statistical procedure for partitioning spatial variation in biolog- ling Thymallus arcticus, rainbow smelt Osmerus mordax,roundwhitefish ical communities along a set of environmental gradients (Legendre et al., Prosopium cylindraceum, longnose sucker Catostomus catostomus and 2005). DCCA was carried out on log-transformed abundance data in burbot Lota lota, together explaining less than 3% of total catch (Table 2). CANOCO software v4.5 (ter Braak and Smilauer, 2002). To avoid potential Marine and anadromous fish were the dominant life-history types distortion introduced by infrequent taxa (Legendre and Legendre, 1998), (Table 3). Marine fish including Pacific herring, starry and Arctic floun- only those species that were caught in a minimum of 10 nets der, fourhorn sculpin and the cod group, explained the larger fraction

(%Freqi ≥ 2%) were included in DCCA. The forward selection procedure (40%) of the total catch and occurred in 34% of experimental nets. Five with Monte Carlo permutation test (2500 permutations, α =0.05)was species of anadromous fish (least cisco, Arctic cisco, broad whitefish, used to assess the significance of environmental gradients (ter Braak inconnu and rainbow smelt) had a similar occurrence in test nets and Smilauer, 2002). DCCA biplots were produced to illustrate species (35%) and explained 31% of the catch. Freshwater-amphidromous fish and sampling sites distributions relative to environmental gradients. Iso- represented by lake whitefish, lake trout, northern pike and round grams of species richness and total CPUE were overlain on DCCA biplots of whitefish, occurred in 29% of the nets and explained 28% of the total the netting sites. Isovalues were fitted by locally weighted regression catch. Freshwater fish included three species (Arctic grayling, longnose (LOESS) procedure (Cleveland, 1979) using CanoDraw for Windows sucker, and burbot) which occurred in only 2% of the nets and contrib- v4.14 (ter Braak and Smilauer, 2002). uted limited (b1%) catch.

Results Species–environment associations

Spatial variation in environmental variables Four species (burbot, longnose sucker, rainbow smelt and round whitefish) had a frequency of occurrence b 2% in experimental nets Cluster analysis distinguished three areas characterized by similar and were excluded from DCCA. Net depth, salinity, temperature and environmental conditions in Husky Lakes (Fig. 2). Area A at the head pH gradients were retained in the final DCCA and the ordination of the estuary comprises the inner-most basins up to the inner fingers explained a significant proportion of the overall variance (Monte Carlo region and was characterized by average oligohaline (b5 ppt) salinities permutation tests n = 2500, p b 0.001). Distance from mouth was

Table 1 Results of multivariate hierarchical clustering of the netting sites (Duda–Hart index and pseudo T-square values) and summary of environmental variables among the resulting clusters (areas). n = number of experimental net sets. Areas A, B and C as in Fig. 2. Distance is from Thumb Island (Fig. 1).

Clustering indices Environmental variables

Area n Je(2)/Je(1) Pseudo T-sq Distance (km) Net depth (m) pH Temperature (°C) Salinity (ppt)

Mean Min Max Mean Min Max Mean Min Max Mean Min Max Mean Min Max

A 160 0.34 1019.36 93.4 68.9 125.7 5.2 1.0 27.0 7.8 6.9 8.3 10.1 5.3 15.8 4.4 0.5 11.5 B 146 0.23 1216.92 55.3 36.3 70.4 5.2 0.5 22.0 7.9 7.1 8.8 8.9 6.0 14.5 10.2 6.7 13.0 C 217 0.42 219.60 17.0 1.0 36.6 5.2 1.0 21.0 7.3 6.6 9.0 8.1 1.9 18.3 12.5 1.8 17.4

strongly, negatively correlated to salinity (r = −0.84, p b 0.001) and Richness was higher (smoothed average ≥ 2) at higher salinities and positively correlated to temperature (r =0.40,p b 0.001) and pH lower pH near the mouth of the estuary in area C, and increased with (r = 0.36, p b 0.001), and was removed from DCCA over concerns temperature at the head in area A (Fig. 4a). High richness was also about multicollinearity (Legendre and Legendre, 1998). observed in a few nets associated with lower salinity and warmer tem- The first two DCCA axes explained 11% of the variation in species peratures in Kugaluk Channel in area C (Fig. 4a). Total abundance of fish distribution (9% and 2%, respectively) and 84% of the cumulative cons- was generally high (average 6 fish per net hour) near axis 1 but de- trained variance in species abundance–environmental variables (68% creased in either direction along axis 2 (Fig. 4b). Maximal abundance and 16%, respectively) (Table 4). Species–environment correlations (6.4 fish per net hour) was observed at lower salinities and warmer were equivalent to 85% and 45% on the first and second canonical temperatures at the head of the estuary in area A (Fig. 4b). Lower abun- axes, respectively. Salinity was strongly, negatively correlated to the dance was associated with higher pH in areas B and C (Fig. 4b). first axis and was thus the most important environmental variable determining variation in species abundance along axis 1 (canonical Discussion coefficient −1.704). Variation along axis 2 was mainly determined by the pH gradient (positive correlation, canonical coefficient 1.154). The Husky Lakes sustain an abundant and diverse fish community, Temperature had a second-order influence on both canonical axes. consistent with observations of local fishers and previous studies The influence of net depth was negligible. in the region (Carmack and Macdonald, 2008; ILA, Inuvialuit Land Ad- DCCA ordination biplots of sampling locations and fish species orga- ministration, 2011). As observed in other northern, temperate and sub- nization along environmental gradients are shown in Fig. 3. The salinity tropical estuaries (e.g., Morin et al., 1980; Whitfield, 1999; Methven gradient distinguished between experimental nets at the head of the et al., 2001; Eick and Thiel, 2014), the fish community in Husky Lakes estuary (area A) and those located near the mouth (area C) or in the was dominated by only a few species. Co-dominance of salmoniforms middle section (area B) (Fig. 3a). Area C comprised netting sites at (Genus Coregonus) and a marine schooling fish (Pacificherring)charac- the positive extreme of the salinity gradient as well as a few sites that terized the ecosystem in early-summer. Salmoniforms occur throughout were negatively correlated to salinity and positively correlated to tem- the Arctic, have the highest species richness among Arctic fish, and perature, corresponding to Kugaluk Channel (Roux et al., 2014). constitute pivotal species in aquatic ecosystems as well as being central A group of four species was strongly associated with low salinities species in Arctic fisheries (Power, 1997; Reshetnikov, 2004; Reist et al., (Fig. 3b). This group included (by order of increasing distance from 2006). Coregonids from all three genera (Coregonus, Prosopium and the origin): lake whitefish, northern pike, lake trout and Arctic grayling. Stenodus) were found in Husky Lakes. These fish are ubiquitous in coastal Among species occurring at higher salinities, three were associated with waters of the Beaufort Sea in Canada and Alaska (Alexander, 1975; Craig, higher pH and cooler temperatures (fourhorn sculpin, Arctic cisco, and 1984; Reist and Bond, 1988), and in estuaries along the Russian coast the cod group). Others were mainly associated with lower pH (Pacific of the Arctic Ocean (Novikov et al., 2000; Reshetnikov, 2004). Coregonids herring, starry flounder, broad whitefish, Arctic flounder, least cisco, exhibit facultative life histories and various degrees of polymor- and inconnu) (Fig. 3b). phism making them well adapted to the changing conditions and the

Table 2 Summary of catch, CPUE, frequency of occurrence (Freq), index of relative importance (IRI), incidence and life history types for ﬁsh species in Husky Lakes (by order of decreasing incidence). A = anadromous; FA = freshwater-amphidromous; F = freshwater and M = marine. See Materials and methods section for IRI thresholds used in ranking incidence.

Common name Scientiﬁc name Family Code Catch % Catch Freq % Freq IRI % IRI CPUE Life history Incidence

Lake whitefish Coregonus clupeaformis Salmonidae LWF 1425 23.96 250 47.80 1145.20 35.59 2.25 FA Dominant Least cisco Coregonus sardinella Salmonidae LC 1035 17.40 224 42.83 745.27 23.16 1.81 A Dominant Pacific herring Clupea pallasii Clupeidae PAH 1505 25.30 142 27.15 686.99 21.35 2.28 M Dominant Arctic cisco Coregonus autumnalis Salmonidae AC 617 10.37 145 27.72 287.59 8.94 0.96 A Common Starry flounder Platichthys stellatus Pleuronectidae SF 519 8.73 136 26.00 226.90 7.05 0.80 M Common Lake trout Salvelinus namaycush Salmonidae LT 135 2.27 82 15.68 35.59 1.11 0.18 FA Occasional Arctic flounder Pleuronectes glacialis Pleuronectidae AF 162 2.72 48 9.18 25.00 0.78 0.29 M Occasional Cod spp.a Gadidae COD 102 1.71 57 10.90 18.69 0.58 0.16 M Occasional Broad whitefish Coregonus nasus Salmonidae BWF 104 1.75 51 9.75 17.05 0.53 0.20 A Occasional Fourhorn sculpin Myoxocephalus quadricornis Cottidae FHS 86 1.45 46 8.80 12.72 0.40 0.14 M Occasional Northern pike Esox lucius Esocidae NP 93 1.56 33 6.31 9.87 0.31 0.13 FA Occasional Inconnu Stenodus leucichthys Salmonidae INC 42 0.71 21 4.02 2.84 0.09 0.07 A Rare Arctic grayling Thymallus arcticus Salmonidae AG 48 0.81 18 3.44 2.78 0.09 0.07 F Rare Rainbow smelt Osmerus mordax Osmeridae RBS 60 1.01 5 0.96 0.96 0.03 0.06 A Rare Round whitefish Prosopium cylindraceum Salmonidae RWF 13 0.22 8 1.53 0.33 0.01 0.02 FA Rare Longnose sucker Catostomus catostomus Catostomidae LNS 2 0.03 2 0.38 0.01 b0.01 b0.01 F Rare Burbot Lota lota Gadidae BBT 1 0.02 1 0.19 b0.01 b0.01 b0.01 F Rare

a Cod spp. includes Eleginus gracilis (saffron cod), Gadus ogac (Greenland cod) and Boreogadus saida (Arctic cod).

Table 3 Richness, catch and frequency of occurrence information among life history types of ﬁsh in Husky Lakes.

Life-history type Richness Catch %CatchT Freq %Freq Anadromous 5 1858 31.2 446 35.1 Marine 5 2374 40.0 429 33.8 Freshwater-amphidromous 4 1666 28.0 373 29.4 Freshwater 3 51 0.9 21 1.7

unpredictable character of Arctic environments. Coregonids also play a major role as energy conveyors in Arctic aquatic food webs (Reshetnikov, 2004), namely in the mobilization and transfer of benthic energy pathways (Roux et al., 2014). Lake whitefish and least cisco had a higher incidence and may occur as species complexes (i.e., co- existence of freshwater and anadromous forms), enabling them to occupy a variety of habitats (Reist and Bond, 1988; Brown et al., 2007). The high abundance and widespread distribution of lake whitefish in the estuary indicate that this might be the case (see Roux et al., 2014 for distribution map). Least cisco and Arctic cisco have known spawning grounds in the Mackenzie River and its major tributaries and migrate along the Beaufort Sea coast during summer and autumn (Craig, 1984; Reist and Bond, 1988). These fish use the Husky Lakes as a summer feeding ground and possibly for overwintering, as Arctic cisco have been shown to overwinter in nearby Tuktoyaktuk Harbour (Bond, 1982; Harwood et al., 2008), in bays and lagoons of Richard Is- land (Reist and Bond, 1988), and presumably in Liverpool Bay (Bond and Erickson, 1993). High incidence of Pacific herring distinguishes the Husky Lakes from other brackish-water ecosystems in the Beaufort Sea region (Craig, 1984; Cobb et al., 2008), and is linked to unique habitat characteristics. Large schools of Pacific herring use the Kugaluk Channel and outer fingers area for spawning (in spring) and overwintering (Gillman and Kristofferson, 1984; Shields, 1988; Bond and Erickson, 1993). This part of the estuary is distinctively shaped as a series of narrow peninsulas with a complex bathymetry (mean and maximum depths of 18 m and 73 m, respectively), and is subject to important water mixing phenomena involving cold saltwater intrusions from Liv- erpool Bay and freshwater plumes from the Miner and Kugaluk rivers (Roux et al., 2014). Pacific herring contribute substantial marine subsi- dies to Husky Lakes (Roux et al., 2014).

fi Fish assemblage structure and environmental gradients Fig. 3. DCCA biplots of a) experimental nets (distinguished by areas) and b) sh species relative abundance (species code) relative to environmental gradients (arrow vectors). Arrow length and direction indicate the relative importance and direction of change Of the environmental variables considered in this study, salinity had (low-high) in the environmental variables. The perpendicular distance between a species the greatest influence on fish species distribution and abundance, code and a vector is proportional to the influence of that vector on that species. The coordinates of origin correspond to the mean value for all vectors. Species codes are given in Table 2.

Table 4 fi Summary statistics of DCCA of sh relative abundance and environmental (env.) variables. consistent with fish communities from other estuaries (Whitfield, Total inertia = 4.035. 1999; Jaureguizar et al., 2004; Eick and Thiel, 2014). Water temperature Axis 1 Axis 2 and pH gradients determined spatial variation in richness and total Eigenvalue 0.372 0.088 abundance. In tropical, sub-tropical and temperate estuaries, dissolved Species-environment correlations 0.792 0.452 oxygen and turbidity gradients are also important determinants of fish Cumulative percentage variance community structure (Whitfield, 1999; Mendoza et al., 2009; Eick and Explained by species 9.2 11.4 Thiel, 2014). In Arctic aquatic systems characterized by oligotrophic, Explained by species-env. variables 67.6 83.6 fl Intra-set correlation (env. variables) well oxygenated clear waters, the in uence of thermohaline properties Salinity −0.733 0.018 tends to prevail (Morin et al., 1980; Griffiths et al., 1998; Abookire et al., Temperature 0.318 −0.106 2000; Jarvela and Thorsteinson, 1999). Cold temperatures increase pH 0.278 0.396 oxygen solubility in polar waters and decrease the oxygen requirements Net depth 0.056 0.017 fi Canonical coefficients (env. variables) of polar ectothermic organisms, including shes (Roessig et al., 2004). The Salinity −1.704 0.403 occurrence of consistently high dissolved oxygen concentrations with Temperature 0.690 −0.082 increasing depth in Husky Lakes was demonstrated by Carmack and pH 0.109 1.154 Macdonald (2008). Weak gradients in dissolved oxygen were deemed Net depth 0.049 0.013 unlikely to influence early-summer fish species composition/distribution

Macdonald, 2008). In a study of subarctic estuarine fish communities of the eastern James-Hudson Bay coast, Morin et al. (1980) found a reduction in the number of freshwater species with increasing latitude, in favour of species more strongly euryhaline. The authors hypothesised that this pattern was caused by a lack of adequate habitat and/or enhanced competition with diadromous species in the northern- most systems (Morin et al., 1980). Both factors (habitat limitations and community interactions) are likely to constrain freshwater fish abundance in Husky Lakes. Species with limited salinity tolerance (Arctic grayling, lake trout, northern pike and lake whitefish) were mainly encountered in oligohaline (≤5 ppt) waters at the head of the estuary, wheretheyoccurredinhighabundance(Roux et al., 2014). These fish are at the northern limit of their distribution range in Husky Lakes, where estuarine conditions offer limited freshwater habitat but potentially abundant food supplies in comparison with large northern lakes. Salinity constrained the abundance of lake trout and northern pike to a similar degree, and was highly limiting for Arctic grayling. The occurrence of Arctic grayling was closely linked to the availability of freshwater habitat in the upper reaches of the estuary. Other rare freshwater/freshwater-amphidromous species not sampled in large enough numbers for DCCA (burbot, longnose sucker and round whitefish), probably share a similar or more restricted range. Lake trout are considered a freshwater species (Scott and Crossman, 1973), but have been documented to undertake occasional migrations to brackish water environments in Western Arctic areas (Harwood et al., 2008; Swanson et al., 2010). Results from otolith strontium analyses indicated that the majority (e.g., 85%) of lake trout from Husky Lakes spawn and spend their entire lives in brackish waters (Kissinger et al., 2015). Herein, species–environment correlations indicate that increasing salinity was clearly a limiting factor to lake trout abundance and distribution in Husky Lakes. The species was absent seaward of the inner fingers area, where average salinities exceeded 8 ppt and minimum salinities were above 6 ppt (Roux et al., 2014). Thus, the Husky Lakes support an entirely brackish water resident form of lake trout, whose abundance and distribution are however constrained by the availability of oligohaline waters. Low salinities constrained the abundance and distribution of Arctic flounder, cods and least cisco. Other anadromous and marine species exhibited flexible salinity preferences seemingly well-adapted to the brackish conditions encountered in the intermediate and outer sections of Husky Lakes. Differences in salinity tolerance might distinguish marine and anadromous fishes more strongly associated with the estuarine environment for overwintering, spawning and/or juvenile rearing (i.e., Pacific herring, Arctic cisco, starry flounder, broad whitefish and fourhorn sculpin), from species that mainly use the estuary as a seasonal feeding ground (i.e., Arctic flounder, cods and least cisco). Fig. 4. Isograms of a) species richness and b) total (all species) CPUE overlain on DCCA fl biplots of the netting sites (as distinguished based on cluster areas shown in Fig. 2). Starry ounder juveniles remained in estuarine waters of the Bol'shaya Isovalues were generated by LOESS. River Estuary (Western Kamchatka) up to about four years old, while adults only periodically entered the estuary for foraging (Tokranov and Maksimenkov, 1994). Broad whitefish associations with estuarine in the estuary. Turbidity may have seasonal effects on the fish communi- environments were demonstrated in Siberia and in the Yukon and Mac- ty, considering several river plumes that either directly or indirectly enter kenzie rivers of North America (Berg, 1962; Reist and Bond, 1988). the estuary during the open-water season. Unfortunately, too few turbid- Fourhorn sculpin is a non-migratory fish commonly encountered in ity measurements were available to assess turbidity effects in this study. Arctic estuaries (Khlebovich, 1997), and a probable estuarine spawner The co-occurrence of staple northern lakes species (lake trout, (Morin et al., 1980). northern pike and Arctic grayling) with marine demersal fishes (Arctic Cold water associations influenced the distributions of fourhorn flounder, starry flounder and cods) in Husky Lakes was permitted by a sculpin, cods and Arctic cisco. The abundance of cods and Arctic cisco horizontal salinity gradient almost identical to that observed during was also linked to the occurrence of slightly alkaline water. Differences winter months by Macdonald et al. (1999) and Carmack and Macdonald in optimal/preferred salinity, pH and temperature ranges between (2008) (with the exception of lower salinities near the mouth in our Arctic cisco and least cisco may reflect differences in habitat use and/or study). This suggests that salinity, and therefore fish species composition, habitat segregation between these two species in Husky Lakes. are relatively conservative properties in Husky Lakes. Despite its importance in determining the spatial distribution of Freshwater fishes had comparatively low incidence, suggesting fish species, salinity had only limited influence on richness and total that freshwater habitat is generally limiting, even in early-summer abundance. With 19 identified species, richness was equivalent to when freshwater influx (from ice melt and runoff sources) should be about one sixth the total numbers of fish taxa known to occur in marine at, or near, the annual peak (Macdonald et al., 1999; Carmack and and brackish waters of Arctic Canada (McAllister, 1977; McAllister et al.,

1987). These Arctic-wide numbers tend to be inflated, however, by the Our near-shore sampling method also probably underestimated occurrence of combined Arctic and Atlantic influences supporting the occurrence of marine demersal species such as flatfishes (Arctic mixed Arctic/subarctic and temperate fish fauna in the eastern regions flounder and starry flounder), sculpins and cods. Together, these fish (i.e., James-Hudson Bay, northern Quebec and Labrador coast). Where accounted for the majority of the catch in small-mesh beam trawls in true Arctic conditions prevail as they do in Husky Lakes, fish richness a study of near-shore fish distributions in an Alaskan estuary (Abookire is generally much lower. Novikov et al. (2000) identified a total of et al., 2000). The fourhorn sculpin had a high occurrence in estuaries 21 fish species across 13 estuaries of the Russian Arctic coast. While of the Russian Arctic Coast (Novikov et al., 2000)andwasabundantin sampling may have been incomplete, maximum richness per estuary estuaries of the eastern James-Hudson Bay and Alaskan coasts (Morin did not exceed 10 species (Novikov et al., 2000). Unfortunately, limited et al., 1980; Griffiths et al., 1998; Jarvela and Thorsteinson, 1999). data and information on fish assemblages in Arctic regions are presently Although the life histories and distribution of Arctic flatfishes and cods available for comparisons. In Husky Lakes, richness was low compared are poorly documented and although they often occur in low abundance to temperate or tropical estuaries where it may range from 30 to over and are of little commercial value, they hold considerable ecological im- 70 fish species (Mendoza et al., 2009; Jaureguizar et al., 2004; Eick portance in the Arctic marine food webs, and probably in Husky Lakes and Thiel, 2014), but richness was similar to Liverpool Bay (Bond and also. These fish are major consumers of benthos and/or zooplankton, Erickson, 1992, 1993), Tuktoyaktuk Harbour (Harwood et al., 2008) and are key prey items for fish, birds and mammals (Atkinson and and Alaskan Beaufort Sea coastal waters (Jarvela and Thorsteinson, Percy, 1992; Logerwell et al., in press). 1999). Diverse fish assemblages occur in coastal areas of the Beaufort Sea Implications for future monitoring of Husky Lakes and similar Arctic during summer (Craig, 1984; Bond and Erickson, 1997; Cobb et al., aquatic ecosystems 2008), which serve as migratory corridors and important summer feeding grounds for adult and juvenile fish, provide overwintering habitat in Fish community structure in estuaries is shaped by a set of environ- some species, and may ensure connectivity between the Mackenzie mental variables and the life history patterns of the various species River, Tuktoyaktuk Harbour, Liverpool Bay and Husky Lakes. Because (Whitfield and Elliot, 2002). Monitoring the assemblage of fish species the Husky Lakes are highly oligotrophic (Evans and Grainger, 1980; provides a means to examine changes in the ecosystem because fish Grainger and Evans, 1982; Roux et al., 2014), connectivity to nearby act as tractable links to the surrounding catchment, freshwater, marine ecosystems, together with species life history diversity, probably deter- and fluvial environments. Fish community structure has often been mines richness and abundance of fish in the estuary. Localized, spatial used to illustrate changes in environmental conditions (Whitfield, variations were related to temperature and pH gradients, with mixing 1996; Elliott and Hemingway, 2002; Griffiths et al., 1998; Nyitrai et al., conditions (i.e., average pH and temperature values), promoting higher 2012), with fish species acting as ‘sentinels’ through their responses to richness and total abundance. An important exception to this, however, changes and variation in the environment. was the observation of higher fish abundance in low salinity, warmer The environmental variables considered in this study will be directly waters at the head of the estuary, where a narrow suite of environmental or indirectly influenced by climate changes that affect precipitation and conditions instead supported a higher abundance of fish with compara- evaporation rates, permafrost and erosion, surface runoff, oceanic tively narrow physiological ranges (i.e., freshwater and freshwater- volume and pH, and snow and ice accumulation (Roessig et al., 2004; amphidromous species). Pörtner and Peck, 2010) as well as by enhanced anthropogenic develop- The influence of pH may be confounding because pH minima/maxima ment and resource usage leading to catchment alterations, shoreline may reflect differences in contributing water types (i.e., river plumes disturbances and erosion, and changes in the magnitude and composi- originating from wet acidic or wet alkaline tundra drainage, Rember tion of freshwater runoff. Cause–effect mechanisms and directional and Trefry, 2004) and the occurrence of physico-chemical processes changes in salinity, temperature and pH gradients as a result of the such as photosynthesis and respiration which can modify pH (Skirrow, aforementioned factors, remain difficult to establish in Arctic aquatic 1965; Wetzel, 1983). Without knowledge and monitoring of water pH systems (Roessig et al., 2004; Reist et al., 2006; Pörtner and Peck, in river effluents and marine waters entering the estuary, fish species 2010). The understanding of fish community organization along those association with pH is difficult to interpret. Inconnu abundance was gradients, however, can serve to better anticipate changing conditions distinctively associated with low pH water, presumably of riverine origin, and potential impacts on ecosystem function and integrity. as the timing of sampling coincided with the likely onset of upstream Fish utilize the Husky Lakes for foraging, spawning, rearing and spawning migrations for the species (Alt, 1977). In contrast, affinities overwintering. Changes in salinity gradients resulting from climate or for lower pH in Pacific herring, starry flounder and broad whitefish anthropogenic stressors, alone or in combination, will impact freshwa- most likely reflect marine associations, similar to Arctic flounder. ter, brackish and marine habitat availability in the estuary. This will affect feeding opportunities for fish, including prey distribution and Study limitations abundance, and key life processes such as recruitment, growth and migrations (Roessig et al., 2004; Reist et al., 2006; Gillson, 2011; There were a number of size and habitat selectivity limitations Morrongiello et al., 2014). The estuary supports highly adaptable migra- associated with our sampling method. Fish species that were smaller tory species (e.g., anadromous coregonids, Pacific herring), and species than 15 cm (total length) were poorly represented in gill nets (Morin with narrow and more specific habitat requirements (e.g., lake trout, et al., 1980). Thus, smaller-bodied species and juvenile life stages of Arctic grayling). Both types have a high importance culturally and eco- larger-bodied species were probably not vulnerable to the gear in our nomically to local Inuvialuit fishers (Joint Secretariat, 2003; ILA, study. Hence, the ninespine stickleback Pungitius pungitius, which was Inuvialuit Land Administration, 2011), and in the maintenance of aquatic found in the stomachs of lake trout in the estuary (Roux et al., 2014), biodiversity. The latter group are the most vulnerable species to envi- was not caught in the experimental nets. Incomplete sampling of ronmental change or perturbations (Henley et al., 2010). smaller-size fish has implications for community richness (which may Evidence of limited seasonal variations in the horizontal salinity be underestimated) and for relative abundance estimates of species gradient of Husky Lakes is expected to result in some consistency in whose juveniles were present but not captured (e.g., Pacific herring). the fish community structure throughout the year. In contrast, temper- In both temperate and tropical regions, estuaries are important rearing ature and pH gradients, which we have shown to affect richness and areas for juvenile fish (Whitfield, 1999; Methven et al., 2001; Franco total abundance, are subject to important seasonal variation unaccounted et al., 2008). Whether or not high Arctic estuaries play a similarly impor- for in this study. Seasonal contraction/expansion of near-shore habitats tant role (or to a similar extent) remains to be demonstrated. with the annual freeze–thaw cycle, will determine intra- and inter-

Please cite this article as: Roux, M.-J., et al., Early summer near-shore fish assemblage and environmental correlates in an Arctic estuary, J. Great Lakes Res. (2015), http://dx.doi.org/10.1016/j.jglr.2015.04.005 M.-J. Roux et al. / Journal of Great Lakes Research xxx (2015) xxx–xxx 9 specific interactions and resource partitioning, especially among fresh- environmental change (Whitfield and Elliot, 2002; Roessig et al., water and freshwater-amphidromous species in the inner basins. 2004; Pörtner and Peck, 2010). As such, and because of the practical, Density-dependent effects, together with limited freshwater habitat temporal and economic constraints associated with conducting availability, may restrain the incidence of freshwater fish in the estuary ecosystem-wide surveys of fish communities in Arctic regions, the (Morin et al., 1980). Seasonal variations in the abundance of marine monitoring of indicator fish species may provide a realistic and effective and anadromous fishes are expected to be important and related to means of detecting ecosystem changes. Indicator species are key biolog- life-history migrations, the presence/absence of migratory corridors to/ ical elements of an ecosystem that serve to evaluate the fundamental from the Husky Lakes, and the availability of preferred or suitable habitat condition of the environment without having to capture the full com- for overwintering. The presence and extent of migratory corridors are plexity of the system (Whitfield and Elliott, 2002). As the species likely to be affected by climate-driven increases in oceanic volume and most closely associated with freshwater habitat in the innermost basins, sea level rise leading to increasing water column depth in coastal envi- the abundance and distribution of Arctic grayling are key to monitoring ronments (Roessig et al., 2004). changes in the salinity gradient and freshwater habitat availability at The innermost basins of Husky Lakes are of particular significance to the head of Husky Lakes. In addition, formal, standardized and long- fish community structure and ecosystem functioning. The area provides term monitoring of the catch rates of lake trout in the subsistence fish- refuge habitat for freshwater species and had the highest abundance ery, may provide a practical means of detecting changes in low salinity of fish in early summer compared to all other areas of the estuary. Re- (oligohaline) habitats and associated species distributions in the estu- ductions in freshwater inflows to the innermost basins, as a result of ary. Another potentially useful indicator species is Pacific herring, climate or anthropogenic forcing, are likely to imperil the already- whose occurrence is closely associated with the environmental condi- limited freshwater fish habitat, as well as impacting the important tions at the mouth of the estuary. Spawning habitat for Pacific herring traditional subsistence fishery that occurs annually in this area (Roux has a high value to the near-shore fish community and probably the en- et al., 2014). Freshwater flow is a strong determinant of fish community tire ecosystem. Spawning occurs immediately prior to ice break-up in structure in estuaries, as it affects habitat and prey availability, commu- June (Gillman and Kristofferson, 1984; Shields, 1988), and is thus relat- nity interactions, and recruitment success in some species (Hurst et al., ed to the annual freeze–thaw cycle. Persistent changes in the timing of 2004; Gillson, 2011; Nyitrai et al., 2012; Morrongiello et al., 2014). ice break-up and/or unusual fluctuations in water temperature, pH and The protection of natural flow regimes has been suggested as an effec- salinity in Kugaluk Channel and the outer fingers area, could affect tive management strategy for maintaining fish community integrity spawning and recruitment success of Pacific herring and ultimately its and the production of estuarine fisheries (Gillson, 2011). Such strategy abundance in the estuary. Least and Arctic ciscoes may also be useful in- may be especially useful for the conservation and management of dicator species considering their high incidence and contrasted physio- lake trout resources in Husky Lakes. Climate changes leading to locally logical ranges. Both species integrate environmental information from enhanced precipitation and freshwater runoff may contribute to regional coastal, fluvial and catchment ecosystems, as well as local estu- expanding freshwater habitat in the estuary (Roessig et al., 2004; arine conditions. Changes in the relative abundance of anadromous Gillson, 2011). Alternative scenarios, however, including local reduc- ciscoes may reflect regime shifts or perturbations in the Mackenzie tions in ice and snow cover leading to greater evaporation and reduced River and coastal Beaufort Sea areas, or local changes in the extent of freshwater input during spring break-up, changes in oceanic volume preferred habitats and community interactions. Increasing water tem- and thermohaline circulation leading to greater marine intrusions peratures, for example, may directly restrain the abundance of Arctic (Roessig et al., 2004; Reist et al., 2006), and infrastructure development cisco in the estuary, or indirectly via habitat limitations leading to a causing shoreline disturbances and enhanced freshwater usage in higher degree of overlap and interference competition with least cisco. catchment areas, will instead contribute potentially significant reduc- tions in freshwater habitat. Small increases in water temperature can have profound impacts Conclusions on the distribution and abundance of fish (Roessig et al., 2004; Reist et al., 2006; Pörtner and Peck, 2010), and promote higher richness in Our study identifies species–environment associations determining Arctic estuaries, as a result of range expansion in migratory species oth- near-shore fish species composition, richness, incidence and relative erwise associated with subarctic and temperate environments (Reist abundance in an Arctic estuary in early summer. High levels of fish et al., 2006; Hiddink and ter Hofstede, 2008). Temperature-enhanced production and species richness were related to the availability of richness may have negative consequences on the occurrence of Arctic freshwater, brackish and marine habitats; connectivity to nearby species (i.e., cods, flounders, coregonids and fourhorn sculpin) and coastal marine and fluvial ecosystems; and fish life-history diversity. overall community interactions. Warming temperatures can also direct- We suggest that the maintenance of these factors (habitat diversity ly, negatively impact the abundance and distribution of stenothermal and connectivity) is key to aquatic biodiversity conservation in coldwater species, including cods, Arctic cisco and fourhorn sculpin in Arctic regions. Several fish encountered in Husky Lakes are staple Husky Lakes, and possibly lake trout and other coregonids (Reist et al., species in marine and freshwater ecosystems in northern environ- 2006), whose association to cold water environments may have been ments. Their co-occurrence in the estuary is permitted by an appar- concealed by the overriding influence of the salinity gradient in the ently conservative salinity gradient, suggesting that community estuary. structure, namely the occurrence of freshwater and freshwater- Climate-driven acidification of marine environments will negatively amphidromous fish,issensitivetochangesinfreshwaterinflows impact the abundance of marine cods and Arctic cisco in Husky Lakes, and marine intrusions. and may favour species having a stronger affinity for low pH water, Further work is required to determine seasonal, temporal, and life- such as Arctic flounder and inconnu. Most importantly however, small stage variations in fish abundance and habitat use, to refine the taxo- changes in pH can affect the embryonic and juvenile life-stages of fish nomic resolution of species complexes, and to characterize the ecological species that use the estuary for spawning and as a rearing area. At pres- processes like competition and predation that also affect community ent, the lack of basic knowledge on fish physiology–habitat interactions structure and ecosystem function. The reference conditions established in the north, limits our understanding of the effects of water pH on the herein, will inform future studies aimed at detecting environmental growth, recruitment and survival of Arctic fish populations (Reist et al., changes in Husky Lakes and similar ecosystems. This will better position 2006). managers and resource users in anticipating and assessing potential Community and population level changes will occur through spe- impacts of climate change and anthropogenic development and activi- cies and individual's physiological and behavioural responses to ties in Arctic aquatic environments.

Acknowledgements Henley, W.F., Patterson, M.A., Neves, R., Lemly, A.T., Dennis, A., 2010. Effects of sedimen- tation and turbidity on lotic food webs: a concise review for natural resource managers. Rev. Fish. Sci. 8 (2), 125–139. http://dx.doi.org/10.1080/10641260091129198. Fieldwork was conducted with the able assistance of Todd Slack, and Hiddink, J.G., ter Hofstede, R., 2008. Climate induced increases in species richness of community technicians including Joseph Felix Jr., Freddie Gruben, marine fishes. Glob. Chang. Biol. 14 (3), 453–460. Hurst, T.P., McKown, E.A., Conover, D.O., 2004. Interannual and long-term variation in the Douglas Panaktalok, Joseph Illasiak Jr., Kyle Kisoun, Clarence Mangelana, nearshore fish community of the mesohaline Hudson River estuary. Estuaries 27 (4), and Forrest Day. The study was supported by the Tuktoyaktuk and 659–669. Inuvik Hunters and Trappers Committees, and funded by the Fisheries ILA (Inuvialuit Land Administration), 2011. Husky Lakes Special Cultural Area Criteria. Joint Management Committee (FJMC), Panel on Energy Research and http://www.inuvialuitland.com/resources/Husky_Lakes_Special_Cultural_Area_ Criteria.pdf. Development (PERD), Devon Canada, ConocoPhillips and the Department Jarvela, L.E., Thorsteinson, L.K., 1999. The epipelagic fish community of Beaufort Sea of Fisheries and Oceans. Data interpolation in ArcGIS was performed by coastal waters, Alaska. Arctic 52, 80–94. Dave Taylor (Taylor Geomatics). The authors wish to thank two anony- Jaureguizar, A.J., Menni, R., Guerrero, R., Lasta, C., 2004. Environmental factors structuring fish communities of the Rio de la Plata estuary. Fish. Res. 66 (2), 195–211. mous reviewers for providing constructive comments on the manuscript. Joint Secretariat, 2003. Inuvialuit Harvest Study, Data and Methods Report 1988–1997. Box 2120, Inuvik, NT X0E 0T0 (202 p). References Khlebovich, V.V., 1997. Selection and criteria for biological indicator species for Arctic monitoring. Mar. Pollut. Bull. 35, 381–383. Abookire, A.A., Piatt, J.F., Robards, M.D., 2000. Nearshore fish distributions in an Alaskan Kissinger, B.C., Gantner, N., Anderson, W.G., Gillis, D.M., Haldern, N. H., Harwood, L. A., estuary in relation to stratification, temperature and salinity. Estuar. Coast. Shelf Sci. Reist, J. D., 2015. Brackish water residency and semi-anadromy in Arctic lake trout 51, 45–59. (Salvelinus namaycush) inferred from otolith microchemistry. Journal of Great Lakes ACIA (Arctic Climate Impact Assessment), 2013. http://www.amap.no/documents/doc/ Research, Special Issue, Large Lakes in Northern Canada. arctic-arctic-climate-impact-assessment/796. Legendre, P., Legendre, L., 1998. Numerical Ecology. Elsevier Science, Amsterdam, The Alexander, V., 1975. Environmental Studies of an Arctic Estuarine System: Final Report. Netherlands. US Environmental Protection Agency (536 p). Legendre, P., Borcard, D., Peres-Neto, P.R., 2005. Analyzing beta diversity: partitioning the – Alt, K.T., 1977. Inconnu, Stenodus leucichthys, migration studies in Alaska, 1961–74. J. Fish. spatial variation of community composition data. Ecol. Monogr. 75, 435 450. Res. Board Can. 30, 129–133. Logerwell, E., Busby, M., Carothers, C., Cotton, S., Duffy-Anderson, J., Farley, E., Goddard, P., Archambault, P., Snelgrove, P.V.R., Fisher, J.A.D., Gagnon, J.-M., Garbary, D.J., et al., 2010. Heintz, R., Holladay, B., Horne, J., Johnson, S., Lauth, B., Moulton, L., Neff, D., Norcross, From sea to sea: Canada's three oceans of biodiversity. PLoS One 5 (8), e12182. B., Parker-Stetter, S., Seigle, J., Sformo, T., 2015. Fish communities of the Beaufort and http://dx.doi.org/10.1371/journal.pone.0012182. Chukchi seas. Prog. Oceanogr. Spec. Issue Synth. Arct. Res. (in press). δ18 Atkinson, E.G., Percy, J.A., 1992. Diet comparison among demersal marine fish from the Macdonald, R.W., Carmack, E.C., Paton, D.W., 1999. Using the O composition in landfast – Canadian Arctic. Polar Biol. 11, 567–573. ice as a record of Arctic estuarine processes. Mar. Chem. 65, 3 24. Barnes, R.S.K., Mann, K.H. (Eds.), 2009. Fundamentals of Aquatic Ecology. John Wiley & McAllister, D.E., 1977. Ecology of the Marine Fishes of Arctic Canada. In Circumpolar Sons. Conference on Northern Ecology Proceedings, Section II. Marine Ecology. National – Berg, L.S., 1962. Freshwater Fishes of the USSR and Adjacent Countries. 4th ed. Israel Program Research Council of Canada, Ottawa, Canada, pp. 49 65. for Scientific Translations, Jerusalem. McAllister, D.E., Legendre, D., Hunter, J.G., 1987. List of Inuktitut (Eskimo), French, English fi Bond, W.A., 1982. A study of the fish resources of Tuktoyaktuk Harbour, southern and Scienti c Names of Marine Fishes of Arctic Canada. Canadian Manuscript Report Beaufort Sea coast, with special reference to life histories of anadromous coregonids. of Fisheries and Aquatic Sciences 1932. vii + 90 p., Can. Tech. Rep. Fish. Aquat. Sci. 1119 (vii + 90 p). Mendoza, E., Castillo-Rivera, M., Zárate-Hernández, R., Ortiz-Burgos, S., 2009. Seasonal Bond, W.A., Erickson, R.N., 1992. Fishery data from the Anderson River Estuary, Northwest variations in the diversity, abundance and composition of species in an estuarine fi fi – Territories, 1990. Can. Manuscr. Rep. Fish. Aquat. 2171 (iv + 46 p). sh community in the tropical Eastern Paci c, Mexico. Ichthyol. Res. 56, 330 339. Bond, W.A., Erickson, R.N., 1993. Fisheries investigations in coastal waters of Liverpool http://dx.doi.org/10.1007/s10228-009-0102-5. fi Bay, Northwest Territories. Can. Manuscr. Rep. Fish. Aquat. 2204 (i–iv +51 p). Methven, D.A., Haedrich, R.L., Rose, G.A., 2001. The sh assemblage of a Newfound- Bond, W.A., Erickson, R.N., 1997. Coastal migrations of Arctic ciscoes in the eastern land estuary: diel, monthly and annual variation. Estuar. Coast. Shelf Sci. 52 (6), – Beaufort Sea. Fish Ecology in Arctic North America. Am. Fish. Soc. Symp. 669 687. fi (No. 19). Morin, R., Dodson, J., Power, G., 1980. Estuarine sh communities of the eastern James- – Brown, R.J., Bickford, N., Severin, K., 2007. Otolith trace element chemistry as an indicator Hudson Bay coast. Environ. Biol. Fish 5, 135 141. of anadromy in Yukon River drainage coregonine fishes. Trans. Am. Fish. Soc. 136, Morrongiello, J.R., Walsh, C.T., Gray, C.A., Stocks, J.R., Crook, D.A., 2014. Environmental ‐ fi 678–690. change drives long term recruitment and growth variation in an estuarine sh. – Carmack, E.C., Macdonald, R.W., 2008. Water and ice-related phenomena in the coastal Glob. Chang. Biol. 20, 1844 1860. region of the Beaufort Sea: some parallels between Native experience and Western Novikov, G.G., Politov, D.V., Makhorov, A.A., Malinina, T.V., Afanasiev, K.I., Fernholm, B., fi – science. Arctic 61, 265–280. 2000. Freshwater and estuarine shes of the Russian Arctic coast (the Swedish ‘ — ’ – Cleveland, W.S., 1979. Robust locally weighted regression and smoothing scatterplots. Russian Expedition Tundra Ecology 94 ). J. Fish Biol. 57 (sA), 158 162. J. Am. Stat. Assoc. 74, 829–836. Nyitrai, D., Martinho, F., Dolbeth, M., Baptista, J., Pardal, M.A., 2012. Trends in estuarine fi Cobb, D., Fast, H., Papst, M.H., Rosenberg, D., Rutherford, R., Sareault, J.E. (Eds.), 2008. sh assemblages facing different environmental conditions: combining diversity – Beaufort Sea large ocean management area: ecosystem overview and assessment with functional attributes. Aquat. Ecol. 46, 201 214. fi fi report. Can. Tech. Rep. Fish. Aquat. Sci. 2780 (ii–ix + 188 p). Pörtner, H.O., Peck, M.A., 2010. Climate change effects on shes and sheries: towards a – Craig, P.C., 1984. Fish use of coastal waters of the Alaskan Beaufort Sea: a review. Trans. cause-and-effect understanding. J. Fish Biol. 77, 1745 1779. fi Am. Fish. Soc. 113, 265–282. Power, G., 1997. Areviewof sh ecology in Arctic North America. Am. Fish. Soc. Symp. 19, – Duda, R.O., Hart, P.E., 1973. Pattern Classification and Scene Analysis. Wiley, Chichester. 13 39. Eick, D., Thiel, R., 2014. Fish assemblage patterns in the Elbe estuary: guild composition, Prowse, T.D., Wrona, F.J., Reist, J.D., Gibson, J.J., Hobbie, J.E., Lévesque, L.M.J., Vincent, W.F., spatial and temporal structure, and influence of environmental factors. Mar. 2006. Climate change effects on hydro-ecology of Arctic freshwater ecosystems. – Biodivers. 44, 559–580. Ambio 35, 347 358. Elliott, M., Hemingway, K.L. (Eds.), 2002. Fishes in Estuaries. Blackwell Science, Oxford. Reist, J.D., Bond, W.A., 1988. Life history characteristics of migratory coregonids of the – Evans, M.S., Grainger, E.H., 1980. Zooplankton in a Canadian Arctic estuary. In: Kennedy, lower Mackenzie River, Northwest Territories. Can. Finn. Fish. Res. 9, 133 144. V.S. (Ed.), Estuarine Perspectives. Academic Press, New York, pp. 199–210. Reist, J.D., Wrona, F.J., Prowse, T.D., Power, M., Dempson, J.B., Beamish, R.J., King, J.R., Franco, A., Elliott, M., Franzoi, P., Torricelli, P., 2008. Life strategies of fishes in European Carmichael, T.J., Sawatzky, C.D., 2006. General effects of climate change on Arctic fi – estuaries: the functional guild approach. Mar. Ecol. Prog. Ser. 354, 219–228. shes and populations. Ambio 35, 370 380. Gillman, D.V., Kristofferson, A.H., 1984. Biological data on Pacificherring(Clupea harengus Rember, R.D., Trefry, J.H., 2004. Increased concentrations of dissolved trace metals and or- pallasi) from Tuktoyaktuk Harbour and the Liverpool Bay Area, Northwest Territories, ganic carbon during snowmelt in rivers of the Alaskan Arctic. Geochim. Cosmochim. – 1981 to 1983. Can. Dat. Rep. Fish. Aquat. Sci. 485 (iv + 22p). Acta 68 (3), 477 489. fi – Gillson, J., 2011. Freshwater flow and fisheries production in estuarine and coastal systems: Reshetnikov, Y.S., 2004. Coregonid shes in Arctic waters. Ann. Zool. Fenn. 41, 3 11. where a drop of rain is not lost. Rev. Fish. Sci. 19, 168–186. Roessig, J.M., Woodley, C.M., Cech, J.J., Hansen, L.J., 2004. Effects of global climate change fi fi – Grainger, E.H., Evans, M.S., 1982. Seasonal variations in chlorophyll and nutrients in a on marine and estuarine shes and sheries. Reviews. Fish Biol. Fish. 14, 251 275. Canadian Arctic Estuary. Estuaries 5, 294–301. Roux, M.-J., Sparling, P., Felix, J., Harwood, L.A., 2014. Ecological assessment of Husky – Griffiths, W.B., Fechhelm, R.G., Gallaway, B.J., Martin, L.R., Wilson, W.J., 1998. Abundance Lakes and Sitidgi Lake, Northwest Territories, Canada, 2000 2004. Can. Tech. Rep. of selected fish species in relation to temperature and salinity patterns in the Fish.Aquat.Sci.3071. Sagavanirktok Delta, Alaska, following construction of the Endicott Causeway. Arctic Scott, W.B., Crossman, E.J., 1973. Freshwater Fishes of Canada. The Bryant Press Limited, 51, 94–104. Ottawa. fi Gushue, W., Carmack, E.C., Macdonald, R.W., 1996. Freshwater inputs to Husky Lakes and Shields, T., 1988. Investigation into the feasibility of establishing sheries for marine fi fi fi Liverpool Bay. Canadian Technical Report of Hydrography and Ocean Sciences 175. shell sh and n sh in the vicinity of Sachs Harbour. Prep. By Archipelago Research Institute of Ocean Sciences, Sidney, B.C. Inc., Victoria, B.C., for Fisheries Joint Management Committee, Rep. 88-002 (67 p. Harwood, L.A., Pokiak, F., Walker-Larsen, J., 2008. Assessment of the subsistence fishery Available: Box 2120, Inuvik, NT Canada. X0E 0T0). and biological data for Arctic cisco in Tuktoyaktuk harbour, NT, Canada, 1997–1999. Skirrow, G., 1965. The dissolved gases-carbon dioxide. In: Riley, J.P., Skirrow, G. (Eds.), Can. Manuscr. Rep. Fish. Aquat. Sci. 2845 (ix + 31 p). Chemical Oceanography. Academic Press, London.

Swanson, H.K., Kidd, K.A., Babaluk, J.A., Wastle, R.J., Yang, P.P., Halden, N.M., Reist, J.D., Whitfield, A.K., 1996. Fishes and the environmental status of South African estuaries. Fish. 2010. Anadromy in Arctic populations of lake trout (Salvelinus namaycush): otolith Manag. Ecol. 3, 45–57. microchemistry, stable isotopes, and comparisons with Arctic char (Salvelinus Whitfield, A.K., 1999. Ichthyofaunal assemblages in estuaries: a South African case study. alpinus). Can. J. Fish. Aquat. Sci. 67 (5), 842–853. Rev. Fish Biol. Fish. 9, 151–186. Tallman, R.F., Abrahams, M.V., Chudobiak, D.H., 2002. Migration and life history alterna- Whitfield, A.K., Elliott, M., 2002. Fishes as indicators of environmental and ecological tives in a high latitude species, the broad whitefish, Coregonus nasus Pallas. Ecol. changes within estuaries: a review of progress and some suggestions for the future. Freshw. Fish 11, 101–111. J. Fish Biol. 61 (Supplement A), 229–250. http://dx.doi.org/10.1006/jfbi.2002.2079 ter Braak, C.J.F., 1986. Canonical correspondence analysis: a new eigenvector technique (2002). for multivariate direct gradient analysis. Ecology 67, 1167–1179. Whitfield, A.K., Harrison, T.D., 2008. Fishes as indicators of estuarine health and estuarine ter Braak, C.J.F., 1994. Canonical community ordination. Part I. Basic theory and linear importance. Encycl. Ecol. 2, 1593–1599. methods. Ecoscience 1 (2), 127–240. Wrona, F.J., Prowse, T.D., Reist, J.D., Hobbie, J.E., Levesque, L.M.J., Vincent, W.J., 2006. ter Braak, C.J.F., Smilauer, P., 2002. CANOCO Reference Manual and CanoDraw for Climate impacts on arctic freshwater ecosystems and fisheries: background, ratio- Windows User's Guide: Software for Canonical Community Ordination (version nale, and approach of the Arctic Climate Impact Assessment. Ambio 35, 326–329. 4.5). Microcomputer Power (Ithaca, NY. 500 pp). Zhu, X., Johnson, T.B., Tyson, J.T., 2008. Synergistic changes in the fish community of ter Braak, C.J.F., Verdonschot, P.F.M., 1995. Canonical correspondence analysis and related western Lake Erie as modified by non-indigenous species and environmental fluctu- multivariate methods in aquatic ecology. Aquat. Sci. 57, 255–289. ations. In: Munawar, M., Heath, R. (Eds.), Checking the Pulse of Lake Erie. Ecovision Tokranov, A.M., Maksimenkov, V.V., 1994. Feeding of the starry flounder, Platichthys World Monograph Series. Aquatic Ecosystem Health and Management Society, stellatus, in the Bol'shaya River Estuary (Western Kamchatka). J. Ichthyol. 34 (1), pp. 439–474. 76–83. Wetzel, R.G., 1983. Limnology. 2nd ed. CBS College Publishing, Philadelphia.