Spawning, overwintering and summer feeding habitats used by anadromous Arctic char (Salvelinus alpinus) of the Hornaday River, Northwest Territories, Canada. (2024)

INTRODUCTION

Arctic char (Salvelinus alpinus) have a circumpolar distributionand are the most northerly distributed species of freshwater fish (Scottand Crossman, 1973). They occur in clear-flowing rivers and lakes of theCanadian Arctic that are located, with two exceptions, east of theMackenzie River (Reist et al., 1997; Reist and Sawatzky, 2010). Ariverine, anadromous (sea-run) stock of Arctic char spawns andoverwinters in the Hornaday River, Northwest Territories, Canada (Fig.1) (DFO, 1999). The Inuvialuit of Paulatuk, a community of 314(Northwest Territories Bureau of Statistics, 2013) located approximately14 km west of the Hornaday River, have harvested char from this systemfor subsistence since the community was first settled in the early1940s. The Hornaday is the largest river draining into Darnley Bay, andit supports the largest stock of Arctic char in the area, with the nextlarge stock located 300 km to the east on Victoria Island (Harwood etal., 2013). A test fishery at the Brock River, the other main riverdraining into Darnley Bay (Fig. 1), confirmed the presence of char inthis system, but only in small numbers (MacDonell, 1988).

Arctic char exhibit several life-history types, the most commonbeing lake-resident (freshwater) and anadromous, with spawning andoverwintering usually occurring in lakes (Johnson, 1980; Tallman et al.,1996; Beddow et al., 1998). In some cases, where lakes are not availableand suitable habitat exists, spawning does occur in rivers (Johnson,1980). Some of the overwintering sites used by Hornaday char are knownthrough the timing and locations of the under-ice fishery conductedannually by the community on the main stem of the Hornaday: TouristCamp, Billy's Creek, and Coalmine (PHTC, 1998; Fig. 1). Nothing isknown of the overwintering potential of areas farther upstream than theAkluk Creek confluence, because the river is prone to unstable iceconditions and therefore not accessible by snowmobile or fishedregularly in winter (Fig. 1). In recent years, char have also beencaught in a winter gillnet fishery from the west channel of the HornadayRiver estuary under a cut-bank where the river does not freeze to thebottom. We refer to this area as the "Bluffs," and locally itis called Nuvaqpaluk (H. Wolki, Paulatuk, pers. comm. 2013; Fig. 1). Thearea has never been the subject of scientific study of either fish orfish habitat.

Spawning and overwintering habitats used by Arctic char are oftenin the same locations since they have similar characteristics (DFO,2004). The choice of specific spawning sites depends on the presence ofa satisfactory substratum, the continuous presence of unfrozen andoxygenated water, and low temperatures (Johnson, 1980; Baxter andMcPhail, 1999). Areas associated with groundwater springs providefavourable habitat for char spawning, egg survival, and hatching(Heggenes et al., 2010), and such areas are also used for spawning andoverwintering by the closely related species Dolly Varden (S. malma)(Sandstrom, 1995; Sandstrom and Harwood, 2002; Mochnacz et al., 2010;Stewart et al., 2010) and bull trout (S. confluentus) in Canada'sNorth (Baxter and McPhail, 1999; Baxter and Hauer, 2000; Mochnacz etal., 2013).

The precise location of spawning areas used by Hornaday char havenot been described, mainly because the river is inaccessible to fishersin September, when the char spawn (Johnson, 1980). The two large lakesdraining into the Hornaday River downstream of La Ronciere Falls, RummyLake and Seven Islands Lake (Fig. 1), are unlikely to provideoverwintering or spawning habitat for anadromous char because of theirsteep, impassible gradients and minimal or non-existent flows inconnecting streams at critical times of year (MacDonell, 1996, 1997).While flows in Rummy and Akluk Creeks (Fig. 1) are too low ornon-existent during summer and fall to permit the upstream passage ofadult char, passage to Seven Islands and Rummy Lakes may be possibleduring spring freshet in some years (MacDonell, 1997; Babaluk et al.,1998).

In spring, anadromous Arctic char (smolts or first-time migrantsand older fish) leave their freshwater overwintering habitats and makeannual migrations to the sea for the important summer feeding period(Johnson, 1980). Char are omnivorous, feeding mainly on small fishes andbenthic organisms in summer, but their diet is highly variable betweenlocations and seasons (Johnson, 1980). They feed in both inter-tidal andsub-tidal habitats (Spares et al., 2012).

Availability of critical habitats and continued access to them areof paramount importance to anadromous char stocks for theirconservation. Northern stocks have especially narrow habitatrequirements for spawning, rearing, overwintering (Stewart et al., 2010;VanGerwen-Toyne and Tallman, 2010), and summer feeding (AANDC, 2012).They are particularly vulnerable to habitat fragmentation anddisruption, and special management or mitigation measures may benecessary if industrial development or other human activities threatentheir habitats. The observations of critical habitats we present herehave not been reported previously for this species in this region, andthey augment a growing natural history baseline for this stock.

Here we collate results from two radio-tagging projects (1995-96and 1999) and two t-bar-tagging projects (1987 and 1997) that aimed toidentify critical overwintering, spawning, or summer feeding habitats ofthe anadromous Hornaday River Arctic char stock. The tagging projectswere conducted jointly with the community fishers, the Paulatuk Huntersand Trappers Committee (PHTC), and the Fisheries Joint ManagementCommittee (FJMC). We were able to rely on local expertise and knowledgeof subsistence fishers to carry out the research. Those involvedrecognized how important understanding aspects of char life history isto ensuring that management initiatives and decisions will conserve thepopulation (PHTC, 1998). One motivation for the tagging projects was tocontribute to informed assessment of potential impacts of proposedmineral exploration activities in the watershed near Coalmine (e.g.,Jones et al., 1992; Darnley Bay Resources Limited, 2013). Another wasthe establishment of the Tuktut Nogait National Park in 1996 (ParksCanada, 1996). Understanding the implications of habitat shifts,critical habitats, and general ecology of this stock is also crucial forassessment of the impacts of a changing climate (Reist et al., 2006;Walsh, 2008; Mochnacz et al., 2010; Stewart et al., 2010).

MATERIALS AND METHODS

Study Area

The Hornaday River (69[degrees]19' N, 123[degrees]48' Wat its mouth) originates in western Nunavut, approximately 100 km northof Dease Arm of Great Bear Lake. It flows in a northwest direction intothe Northwest Territories (NT), through Tuktut Nogait National Park,before emptying into Darnley Bay approximately 14 km east of the hamletof Paulatuk (DFO, 1999; Fig. 1). The river is about 280 km long anddrains an area of 13 120-14900 [km.sup.2] (Ayles and Snow, 2002). LaRonciere Falls (69[degrees]8' N, 122[degrees]53' W), locatedapproximately 45 km from the mouth of the river, is 23 m high, forming abarrier to upstream fish migration (Fig. 1).

Downstream of the falls, the river consists of a mainstem channelof rapids alternating with deep pools that do not freeze to the bottomin winter. There the river is between 40 and 100 m wide and 0.5-3.0 mdeep, with deeper, interspersed groundwater-fed pools in the upperreaches (I. Clark, University of Ottawa, unpubl. data). Preliminaryfield measurements and reconnaissance in 1999 found the dolomite terrainat the Hornaday to be consistent with other sites where there iscontinuous discharge of groundwater through the winter, in regions ofcontinuous permafrost between Coalmine and Akluk Creek (Fig. 1) (I.Clark, unpubl. data; Clark and Lauriol, 1997; Clark et al., 2001; Kaneet al., 2013). Recharge takes place in carbonate karst, through talikzones. Groundwater springs in the upper reaches of the Hornaday are oftypical karst discharge with a Ca(Mg)-HC[O.sub.3] facies, similar to thesituation that maintains open water throughout the winter at FishingBranch River, Yukon Territory (Utting et al., 2013).

There are coal deposits along the Hornaday River near theconfluences of George and Rummy Creeks, at an area locally known asCoalmine (Fig. 1). The Hornaday River delta is approximately 50[km.sup.2] and has several channels, including a shallow, easternchannel that fishers describe as freezing to the bottom in winter, and awest channel that includes a deep pool under the Bluffs (Fig. 1). Themain channel (flow) of the Hornaday River has changed over time;according to fishers, the main flow now favours the west channel overthe previously dominant east channel (H. Wolki, pers. comm. 2013).Downstream of the La Ronciere Falls, the river provides habitat foranadromous Arctic char and several other anadromous and non-anadromousfish species, including Arctic cisco (Coregonus autumnalis), Arcticgrayling (Thymallus arcticus), broad whitefish (C. nasus), burbot (Lotalota), longnose sucker (Catostomus catostomus), and ninespinestickleback (Pungitius pungitius) (DFO, 1999).

Radio Tagging and Tracking

From 15 to 21 August 1995, 21 Arctic char were captured using 127mm (5-inch) stretched-mesh gillnets near the Tourist Camp site on theHornaday River (Fig. 1, Table 1). From 29 July to 10 August 1999, eightArctic char were captured using 127 mm (5-inch) stretched-mesh gillnetsin the pool at the base of La Ronciere Falls (n = 3) and in the eastchannel of the Hornaday River estuary (n = 5) (Fig. 1, Table 2). Aftercapture, the char were anaesthetized with benzocaine, measured (forklength, nearest mm), and weighed (nearest 50 g; 1995 only), and wherepossible, sex was assigned by visually inspecting presence or absence ofa developing kype. Subsistence fishers also checked the fish theycaught, and in most cases were able to determine sex of the fish.

High-frequency radio transmitter tags (model 2, Advanced TelemetrySystems, Inc., Isanti, Minnesota), compressed cylinders, each of whichwas 66 mm long, weighed 20 g, and had a unique frequency signal, weremounted on the right side of each fish just below the dorsal fin(Winters et al., 1978; Mellas and Haynes, 1985). Tags were all withinthe range from 0.4% to 1.1% of body weight, which is below therecommended percent of body weight (Brown et al., 1999). The frequencyrange for the tags was 48.070-48.700 MHz (1995) and 48.674-48.764 MHz(1999). The 48 MHz frequency range is commonly used in rivers because ofrelatively low signal attenuation (Bagliniere et al., 1991). These tagsare detectable in brackish water, although not useful in the oceanbecause detection distances decrease with increasing conductivity(salinity) (Shroyer and Logsdon, 2009). The transmitters had a predictedoperational life of approximately 365 days.

After tagging, the char were kept for at least 24 h in atraditional, boulder holding pen in the river until they had fullyrecovered and then released. Our goal was to capture and tag mature fishin spawning condition; however, these occur in such low numbers in thelate summer upstream Hornaday River run (< 1%) (Harwood, 2009) thatnone were caught during the duration of the project. Only mature,resting fish that would not spawn in that particular year, which werefer to as current year non-spawning char, were captured for tagging(size range = 526 to 730 mm, 1750 to 4850 g; Tables 1 and 2). Radio tagswere tested with a receiver three times: before application, while thetagged fish were in the recovery pen, and immediately after theirrelease into the river. All radio tags were functioning at the time ofrelease.

Tracking of radio-tagged Hornaday River Arctic char was conductedfrom 22 August 1995 to 26 October 1996 and from 1 October to 20 November1999, using both aerial and ground tracking. Aerial tracking wasconducted using a portable receiver from Advanced Telemetry Systems (ATSmodel R2100) from either a Bell Long Ranger helicopter or a fixed-wingCessna 206 airplane. Aircraft were equipped with one or two ATS loopantennae attached forward (helicopter) or to both wing struts(fixed-wing airplane). Ten aerial tracking flights were conducted in1995-96, and each included the Hornaday River from the estuary upstreamto La Ronciere Falls and Rummy and Seven Islands lakes to the extentthat weather and fuel reserves would allow. Aerial flights from Junethrough August 1996 also included all channels in the estuary of theHornaday River, and, on two occasions, the Brock River as far upstreamas its headwater lake (Fig. 1). Tracking was done at altitudes of100-300 m. After the detection of a radio-tagged char, the tag frequencyand location were marked on the field sheet map and GPS coordinates wererecorded from the aircraft's navigation system.

Ground tracking was conducted using the same portable receiver froma snowmobile equipped with a single ATS loop antenna. Three groundsurveys were conducted in 1995-96 and four in 1999 (Tables 1 and 2). Thearea encompassed by each ground survey included the Hornaday River fromthe estuary to near its confluence with Akluk Creek. Tracking was donewhile traveling on river ice and snow at a low speed (< 10 km/h).After the detection of a radio-tagged char, the char's tagfrequency and location were marked on the field sheet map and GPScoordinates were recorded from a hand-held GPS instrument.

Relocations of several radio-tagged char were determined fromtagged fish caught in the local subsistence fisheries at the HornadayRiver from mid-October to mid-November 1995 and in the subsistencefishery along the eastern coast of Darnley Bay in June 1996.

T-bar Tagging and Recaptures

During 21-24 August 1987, 156 Arctic char were captured at aconduit fence weir trap as they were migrating upstream in the HornadayRiver (Fig. 1) (MacDonell, 1988). From 12 July to 6 August 1997, afurther 239 Arctic char were captured using 114 mm (4.5-inch) and 127 mm(5-inch) stretched-mesh, nylon, multi-filament gillnets setperpendicular to shore at Pearce Point (69[degrees]47' N,122[degrees]40' W) (Fig. 1). The trap and nets were checkedregularly (at intervals of about one hour) to avoid damage to the fish(or mortality). Following capture, the char were removed from the trapor nets and placed in holding tubs or pens containing river water. Thechar were handled without anaesthetic.

Captured char were measured (fork length, nearest mm), tagged(t-bar anchor tags, Floy Tag & Mfg., Inc., Seattle, Washington), andreleased. A dead sample of 24 char was taken during the Pearce Pointtagging program (for length, weight, sex, maturity). Stomach contentswere examined and photographed in the field by the communitytechnicians.

The late summer catches from Hornaday River subsistence fisherieshave been enumerated and sampled by community monitors since 1988(Harwood, 2009), which included recording the capture time and locationof any tagged fish. Additional recapture locations and dates were alsoreported directly to DFO and to the monitors by subsistence fishersbetween 1998 and 2005.

RESULTS

Seasonal and Individual-Specific Movements of Radio-Tagged ArcticChar

1995-96: Twenty of 21 Arctic char radio-tagged near Tourist Campfrom 15 to 21 August 1995 were relocated later in 1995 or during thefollowing year (up to 26 October 1996) (Table 1). The longest trackingperiod for an individual fish was 436 days (Table 1, Fish no. 21). Allrelocated (tracking) and captured (subsistence fishery) radio-taggedchar were from the Hornaday River proper or from the sea along thecoast. No radio-tagged char were relocated or captured in the BrockRiver system, from any of the Hornaday tributary creeks (e.g., Akluk,George, Rummy Creeks), or in either of the two larger lakes draininginto the Hornaday River (Seven Islands Lake, Rummy Lake) (Fig. 1).

During late summer and early fall, the relocated radio-tagged charwere found in three general areas in the Hornaday River: 1) in the lowerHornaday River near Tourist Camp (n = 4), 2) farther up the river nearan area known locally as "Billy's Creek" (n = 8), and 3)farther upstream on the main river over a 16 km reach between Coalmineand its confluence with Akluk Creek (n = 5) (hereafter calledCoalmine-Akluk) (Table 1, Fig. 1).

In late fall and winter, radio-tagged char were also relocated inthese three areas of the main-stem of the Hornaday, with most havingreached Coalmine-Akluk by this time (n = 10) (Table 1), and a fewremaining in the lower reaches near Tourist Camp (n = 4) andBilly's Creek (n = 4). Of 12 radio-tagged char that were relocatedduring winter 1995-96 and were not caught in the 1995 upstream migrationfall subsistence fishery, 11 (92%) were eventually relocated during thewinter in the Coalmine-Akluk reach, three of these in consecutive years(Table 1).

In spring and summer, one radio-tagged char was relocated in themain stem of the river approximately 7 km upstream of the First Creekoutflow (Fig. 1, Table 1, Fish no. 13). A further two were captured inthe coastal, spring subsistence fishery following the out-migration, 8km east of the Hornaday River estuary (Table 1, Fig. 1). All other

relocations in spring and summer (n = 6) were at Coalmine-Akluk.

Of the 21 char radio-tagged, three females were relocated multipletimes over a period of 14 months (Table 1). Immediately after tagging,Fish no. 5 (female, 611 mm) moved 5 km downstream, then moved upstreamand was next relocated in the Coalmine-Akluk reach on 11 October 1995,and again on 28 October 1995. In spring of the next year (12 June 1996),this fish was relocated within 4 km of Billy's Creek in the mainstem of the Hornaday. Approximately 10 weeks later (24-25 August 1996),this fish was again relocated at the Coalmine-Akluk area, where itremained (relocated 16 September and 26 October 1996) (Table 1).

Fish no. 6 (female, 620 mm) was relocated four days after tagging,having moved 30 km upstream to the Coalmine area. Its next relocation, 1km upstream of the confluence of the Hornaday River and Akluk Creek on11 October 1995, was the only relocation of a radio-tagged fish fartherupstream than the Coalmine-Akluk reach. This fish was then relocatedeight times in the Coalmine-Akluk reach (in winter 1995-96, summer 1996,and fall 1996), but was not relocated anywhere else (Table 1).

Fish no. 21 (female, 645 mm) was relocated five days after tagging,having moved 8 km upstream in the Hornaday to the First Creek confluencearea (Fig. 1). By 11 October, it was relocated in the Coalmine-Aklukpools, and it was relocated there nine times over winter 1995-96, summer1996, and as late as 26 October 1996, and nowhere else (Table 1).

1999: Of three Arctic char radio-tagged at La Ronciere Falls inlate July 1999, one was relocated four times in October and November1999, downstream of the tagging site in the west channel of the HornadayRiver in the deep pool at the Bluffs (Table 2, Fig. 1). Of five charradio-tagged at the mouth of the Hornaday River in August 1999, twomoved upstream and were relocated during winter in the Coalmine-Aklukreach, and two were relocated on 29 October 1995 in the west channel ofthe Hornaday River estuary at the Bluffs (Table 2, Fig. 1).

Movements of T-Bar-Tagged Arctic Char

1987: Twenty-two (14%) of 156 t-bar-tagged Arctic char released atthe weir site during 21--24 August 1987 (MacDonell, 1988) wererecaptured in the subsistence fisheries over the next two years. Ninewere caught returning from the sea during the August 1988 subsistencefishery in the east channel of the Hornaday River estuary (Fig. 2). Anadditional four were caught in the Hornaday River during the under-icefishery at Billy's Creek (1988) and Coalmine (1989) (Fig. 2). Afurther eight were caught in the coastal subsistence fishery in spring1988 and 1989 at Krutes Creek (Fig. 2) and one tagged char was caught inJune 1989 in Argo Bay (Fig. 2).

1997: Of the 239 Arctic char t-bar tagged and released in the seanear Pearce Point between 12 July and 6 August 1997 (mean fork length =533 mm, range = 358-815 mm), eight were recaptured within one week oftagging at the same location, and re-released. A dead sample consistingof 16 males and eight females had mean fork length 597 mm (range =437-801). Of 24 char dead-sampled in the field by community technicians,11 had stomachs containing fish remains; 11 had invertebrate remains;and two had empty stomachs. Where fish remains were present, capelin(Mailotus villosus) were purportedly dominant.

Between 6 and 25 August 1997, 34 of the 239 (14.2%) Arctic chart-bar tagged at Pearce Point were captured in the subsistence fishery attraditional fishing sites between the Brock and Hornaday Rivers and atthe east channel of the Hornaday River estuary (Fig. 2), approximately85 km shoreline distance from Pearce Point. These char were at large foran average of 26 days (range = 4-53 days) after tagging. A further 24tagged char were caught in the same areas and time of year between 1998and 2001; four were recaptured off the mouth of the Brock River in 1998and 2004; and one was recaptured at Krutes Creek in the west Hornadayestuary during the spring out-migration in 2005 (Fig. 2). No recapturesof 1997 t-bar-tagged char were reported from any area west of theHornaday River estuary.

DISCUSSION

Overwintering

Radio-tagging results demonstrated that the anadromous, riverinestock of Arctic char in the Hornaday River uses deep pools in the mainstem of the river for overwintering. All char radio-tagged at the mouthof the Hornaday River in August 1995 and two of six tagged at the mouthin August 1999 moved upstream during fall to known winter fishing sitesin the Hornaday. Overwintering in rivers is not the most commoncharacteristic among stocks of char found in the Canadian Arctic, whichmostly overwinter in lacustrine habitats. The Kellet River, Nunavut,Arctic char stock has the only other known riverine life history (DFO,2004, 2013).

During late summer and fall, tagged Arctic char were found in thelower regions of the Hornaday River, as this time coincided with thebeginning of the upstream migration when the char were actively movingfrom the sea into the estuary. They were not relocated in any area otherthan the Hornaday main stem downstream of La Ronciere Falls, such as theBrock River system or the Hornaday tributary creeks (e.g., Akluk,George, Rummy Creeks), or in either of the two larger lakes draininginto the Hornaday River (Seven Islands Lake, Rummy Lake).

The reach of the Hornaday River from Coalmine to Akluk Creek wasidentified as particularly important to this stock for overwintering. Of12 radio-tagged char that we relocated during winter 1995, 11 (92%)overwintered there for one or more winters. Char that overwintered inthis reach of the Hornaday used more than one deep pool during thecourse of the winter, and three fish that we were able to track over anannual cycle used the same deep pool in consecutive years. Theoverwintering pools on the reach of the Hornaday River from Coalmine toAkluk Creek correspond to locations where there are at least fiveperennial groundwater-fed deep pools that were sampled in a preliminarystudy in February and July 1999 (I. Clark, unpubl. data).

Until recently it was thought that anadromous Arctic charoverwintered exclusively in freshwater, due to their presumedintolerance of saline conditions at low temperatures (Johnson, 1980,1989; Berg and Berg, 1993). However, some riverine char populations innorthern Norway have been shown to use estuarine waters during thewinter (Jensen and Rikardsen, 2008, 2012). Our results also revealed theuse of the estuary of the Hornaday River during winter 1999. Of six charradio-tagged in 1999, three were relocated during the winter in theBluffs area of the west channel of the Hornaday River estuary, and theothers, in the Coalmine-Akluk reach described above.

Use of this estuarine habitat by Hornaday River Arctic char inwinter is not unknown to the community fishers of Paulatuk, as they havehistorically (1950s) and more recently (2000s) fished the Bluffs area,with approximately 10 gillnet fishers in the area during the winter (H.Wolki, pers. comm. 2013). As the Hornaday River does not freeze to thebottom at the Bluffs (H. Wolki, pers. comm. 2013), it may be similar tothe situation of Lake Herlinveaux in the Northwest Territories--anexpansive, essentially freshwater "lake" that forms in theouter Mackenzie River estuary each winter (Carmack and Macdonald, 2002).Lake Herlin-veaux has limited or no winter connectivity with the oceanbecause of the isolating effect of grounded sea ice.

Our results contrast with the general assumption that Arctic chardo not overwinter in marine waters, an assumption on which management ofArctic char in Canada's Arctic has been based (DFO, 2004, 2013;VanGerwen-Toyne and Tallman, 2010). While the majority of anadromouschar use freshwater lakes for overwintering, the results from theHornaday are unique in Canada's western Arctic and most likelyreflect the plastic life history that allows char to use suitablehabitats, including estuaries, in certain locations. Investigation ofthe Bluffs area with scientific fishing and tagging is warranted, alongwith a study of substrate, depth, salinity, temperature, and oxygenlevels, as information of this type is not yet available for this area.

Spawning Sites

One of our study objectives was to determine the spawning locationsof Hornaday River Arctic char. Unfortunately, we were unable to deployradio tags on mature fish in spawning condition, as none were caughtduring project fishing efforts. They appear to have a life historypattern similar to that described by Johnson (1989) for Nauyuk Lakechar: the char ascend the river in fall, and if mature, do notnecessarily return to the sea the following summer, but remain infreshwater while their gonads develop. After spawning, the char remainin freshwater for another winter before resuming their feeding migrationto the sea the following spring. This life history pattern results in aloss of 30%-40% of their body weight, so they are often in very poorcondition when they first return to the sea (Dutil, 1986) and are knownas "slinks." The observation of slinks in the Hornaday Riverestuary catches in the spring (authors' unpubl. data) and thepaucity (< 1% annually) of current-year spawners in the upstreammigration in August (Harwood, 2009) provide evidence that at least some,and quite possibly the majority, stay in the river during the summerbefore they spawn.

We have obtained circ*mstantial but compelling evidence forspawning activity by Hornaday char in the reach of the river betweenCoalmine and Akluk Creek by examining the relocations of three of thechar radio-tagged in 1995. The areas where these char were relocated inmid-September (our tracking dates coincided with the time of spawningaccording to Johnson, 1980) points to an emerging picture of multiplespawning pools between Coalmine and Akluk Creek. Fish no. 5 showedfidelity to the Coalmine-Akluk overwintering area in fall 1995 and fall1996, and it used at least one of the same pools in two consecutivewinters. Fish no. 6 actually remained in the Coalmine-Akluk area fromlate August 1995 until it was last relocated on 26 October 1996. Fishno. 21 also did not migrate to sea in summer 1996 (Table 1) and spentwhat would be considered the spawning period (from 16 September to 26October 1996) in this area. Specific locations along the Coalmine-Aklukreach that were used by probable spawners were different from eachother, suggesting that there are multiple spawning pools in this reachof the river. In particular, we note that the deep pool closest toCoalmine corresponds to the place where a local fisher caught andreported five spent (post-spawning) char in mid-October 1994 (J.Illasiak, Paulatuk, NT, pers. comm. 1994)

MacDonell (1996) caught five char that were current-year spawners,as well as one slink, at the pool at the base of La Ronciere Falls inJuly 1996. Also, in early September 1997, a single female in spawningcondition was captured in the pool at the base of the falls, and manymore char were observed in the pool at that time (MacDonell, 1996,1997). None of our radio-tagged fish were relocated in the pool at thebase of falls, so we were unable to confirm that this area is possiblyused for spawning or overwintering. While this pool may well be aspawning area for Hornaday char, its importance in relation to theCoalmine-Akluk reach remains unknown. Further study incorporatinggillnetting, angling, snorkeling or scuba diving, and underwaterphotography could be undertaken during mid-September by using ahelicopter to access the falls area.

The spawning and overwintering habitats of the Hornaday River shownin this study support a large (> 15 000; DFO, 1999), geographicallyisolated, and unique stock of Arctic char. A small stock of anadromouschar uses the Brock River, but its relationship to the Hornaday charstock is not well understood. Tracking flights over the Brock Riversystem during our study were possible on only two occasions, and therewere no relocations of radio-tagged char. There is rarely anysubsistence fishing activity in the Brock River itself, since there isno flow in the upper reaches in summer and fall (authors' unpubl.data). A test fishery was conducted at the mouth of the Brock River in1988, and although the size of the stock could not be estimated, the runwas described as small (MacDonell, 1988). While there is evidence thatreproductive adults return (home) to their natal river (Johnson, 1980;Nordeng, 2009), current-year non-spawning fish (juveniles and restingadults) have been shown to stray between adjacent systems foroverwintering (Johnson, 1980; Kristofferson et al., 1984), and thisdispersal may be important in maintaining gene flow (Moore et al.,2013). Straying is usually geographically localized, as are charmovements at sea, and it occurs mainly among stocks that share a commonsummer feeding area (Roux et al., 2011a). Evidence suggests that atleast some non-spawners move between the Hornaday and the Brock Rivers(Roux et al., 2011b), but the extent of this movement is unknown.

Summer Feeding in the Ocean

In spring, anadromous Arctic char (smolts and older fish) leavetheir freshwater overwintering habitats and make annual migrations tothe sea to feed during the summer (Johnson, 1980). They obtain most oftheir annual energy requirements from these forays into coastal watersduring the short open-water season. The energetic gain from thesecoastal summer feeding areas is of primary importance (AANDC, 2012),outbalancing both the energetic and physiological costs of migration andthe increased risk of predation, by giving the anadromous char access toample, rich marine food resources for one to three months (McCart, 1980;Johnson, 1980; Gross et al., 1988; Begout Anras et al., 1999; Rikardsenet al., 2007; Jensen and Rikardsen, 2012). The results of the 1987 and1997 t-bar-tagging studies provided new information about the locationswhere anadromous Hornaday char feed during the summer. The paucity oftag returns on the west side of Darnley Bay (Fig. 1) compared to theeast side of Darnley Bay, where fish were recaptured in each year forseven years after tagging, suggested that the summer migrants travelmainly along the east side of Darnley Bay. This result may be biased byunequal sampling effort (e.g., soak times, fishing locations); however,if anadromous char were present in adequate numbers west of Paulatuk,the local fishers would be fishing there. They do not; instead, theygenerally concentrate coastal fishing efforts to the east of theHornaday River (PFITC, 1998).

Since 14% of the Pearce Point tagged char were caught within threeweeks of tagging near the Hornaday mouth--and nowhere else--it appearsthat the river mouth is an important Hornaday char feeding area insummer. Fishers from Paulatuk, aware of the abundance of char at thislocation during summer, provided the original recommendation to conductthe tagging study there. The study's objective was to determine the"home river" of these char that the fishers knew were veryabundant there in summer (N. Green, Paulatuk, NT, pers. comm. 1996).Pearce Point is an area of known coastal upwelling (Paulic et al.,2011), which makes it a highly productive marine area during summer.

The field analysis of Arctic char stomach contents suggests thatcapelin play an important role as prey used by Hornaday River anadromouschar in the ocean during the summer months, particularly at PearcePoint. With limited data on summer feeding, we know nothing of annualvariability or the extent to which other prey items are used in years ofvariable capelin abundance. Capelin was also reported as the main marineprey of anadromous char returning from the sea in fall to Nauyuk Lake,where no invertebrates were found in char stomachs at that time(Johnson, 1980, 1989). Further studies are warranted on the location andyear-to-year variability of capelin in coastal feeding areas aroundPearce Point and other areas of Amundsen Gulf, as well as the energeticvalue of capelin and other types of potential prey. This informationwould aid in developing strategies to conserve and protect theseimportant habitats.

In conclusion, the particular habitats in the Darnley Bay area thatappear to be of critical importance to anadromous Arctic char are thedeep pools in the Coalmine-Akluk reach of the upper Hornaday River mainstem, which are associated with perennial groundwater springs (spawningand overwintering), and the rich, marine habitats such as Pearce Point(summer feeding). Potential changes to quality or quantity ofgroundwater flowing to the main-stem areas and the deep pools that areassociated with groundwater springs could be studied in winter usingground-penetrating radar to document their exact locations, size andwater depth. Such studies would be useful for future monitoring andprotection of these critical habitats. Similarly, the deep-water areasat the Bluffs appear to be of some importance as overwintering habitat,at least in some years, and perhaps increasingly so in recent years. Forthis area too we require evaluation of salinity, depth, water quality,water quantity, and the extent to which the area is used by Arctic charin other years and in different seasons, as this baseline information isnot currently available.

http://dx.doi.org/ 10.14430/arctic4422

ACKNOWLEDGEMENTS

The cost and challenges of capturing, tagging, and tracking Arcticchar in a remote northern system such as the Hornaday River areconsiderable, and it was only through collaboration with localharvesters and technicians that this study could be successfullyconducted. We report on the work of many people. Foremost, weacknowledge four community field technicians, the late Charlie Ruben,Joseph Illasiak, Ruben Ruben, and the late Nelson Green, all of whomworked tirelessly on various aspects of the capture, tagging, andtracking over the years encompassed by this study. Their dedication andskills ensured the successful and safe conduct of the studies. We alsoacknowledge the late Donovan Dowler (former Vice-Chair Fisheries JointManagement Committee) for his leadership and dedication to the PaulatukArctic char programs. We also gratefully acknowledge the char fishers ofPaulatuk, for turning in recaptured tags, for sharing their ideas, andfor field and administrative assistance with various programs reportedin this paper. In particular, we acknowledge Tony Green, Hank Wolki,Noel Green, Peter Green, John Max Kudlak, Steve Illasiak, Pat Thrasher,the late Greg Green, Ryan Green, and Jason Ruben (our sincere apologiesto anyone we have missed). We also greatly appreciate the skills andefforts of field camp leaders Paul Sparling (White Mountain ConsultingServices, Whitehorse, Yukon) in 1995, and Don MacDonell (North/SouthConsultants Inc., Winnipeg, Manitoba) for leading t-bar andradio-tagging deployment camps in 1987, 1995, and 1999. From ParksCanada, we gratefully acknowledge the support and assistance ofChristian Bucher and from the University of Ottawa, Dr. Ian Clark andDr. Michel Robin, for conducting groundwater studies on the HornadayRiver in 1999. We also acknowledge the directors and staff of thePaulatuk Hunters and Trappers Committee and Fisheries Joint ManagementCommittee for their ongoing support and assistance with these programs.The tagging studies were made possible by funding provided by theFisheries Joint Management Committee, Parks Canada, Fisheries and OceansCanada, the Campfire Club of North America, and the Polar ContinentalShelf Project of Natural Resources Canada. We thank Steve Sandstrom, Dr.Tom Smith, and three anonymous reviewers for helpful comments thatimproved this manuscript.

(Received 30 August 2013; accepted in revised form 19 March 2014)

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LOIS A. HARWOOD (1) and JOHN A. BABALUK (1,2)

(1) Corresponding author; Fisheries and Oceans Canada, 301,5204-50th Avenue, Yellowknife, Northwest Territories X1A 1E2, Canada;[emailprotected]

(2) 217 River Road, St. Andrews, Manitoba R1A 2W3, Canada

TABLE 1. Biological and relocation information of Arctic char radio-tagged at the Hornaday River, 1995-96. Gray shading indicates spawningperiod (where applicable; i.e., September-October 1996) andoverwintering period. Relocation areas: CM = Coastal Marine, HM =Hornaday Mouth (east side of estuary, too shallow for overwintering,probable mortality), TC = Tourist Camp (proximate to Old Weir site),FC = First Creek, BC = Billy's Creek, MS = Main stem, CA = Coalmine-Akluk (upper river), * = caught in subsistence fishery (duringinterval between surveys), ** = too shallow for overwintering,probable mortality.Tag site & date Tourist Camp: 15-21 August 1995Fork length (mm) 720 690 567 605 611 620Weight (g) 4800 3900 2750 2700 2900 3050Sex M M NA M F FFish no. 1 2 3 4 5 6Survey date:22 August 1995 (1) HM HM TC HM MS11 October 1995 (1) CA TC TC CA TC *28 October 1995 (2) CA CA CA CA CA *23 January 1996 (2) CA CA22 February 1996 (2) CA4 May 1996 (1) CA CA12, 19 June 1996 (1) MS CA7 July 1996 (1)2 August 1996 (1) CA24, 25 August 1996 (1) CA CA16 September 1996 (1) CA CA26 October 1996 (1) CA CATag site & date Tourist Camp: 15-21 August 1995Fork length (mm) 720 540 550 708 698 631Weight (g) 4800 2200 1900 5000 4100 2900Sex M F F M M MFish no. 1 7 8 9 10 11Survey date:22 August 1995 (1) FC TC FC HM11 October 1995 (1) BC CA BC BC * BC *28 October 1995 (2) CA23 January 1996 (2) CA22 February 1996 (2) CA4 May 1996 (1) CA HM **12, 19 June 1996 (1) CM*7 July 1996 (1)2 August 1996 (1) HM24, 25 August 1996 (1)16 September 1996 (1) HM26 October 1996 (1) HMTag site & date Tourist Camp: 15-21 August 1995Fork length (mm) 720 694 650 695 535 593Weight (g) 4800 4100 3400 na 1850 2450Sex M M M M M MFish no. 1 12 13 14 15 16Survey date:22 August 1995 (1) FC TC TC CA11 October 1995 (1) BC FC CA TC BC * TC *28 October 1995 (2) FC CA23 January 1996 (2) FC CA22 February 1996 (2) FC CA4 May 1996 (1) CA12, 19 June 1996 (1) CM *7 July 1996 (1)2 August 1996 (1)24, 25 August 1996 (1) FC16 September 1996 (1) FC26 October 1996 (1) FCTag site & date Tourist Camp: 15-21 August 1995Fork length (mm) 720 527 526 730 674 645Weight (g) 4800 2050 1750 4850 3500 3500Sex M NA NA M M FFish no. 1 17 18 19 20 21Survey date:22 August 1995 (1) CA BC FC BC FC11 October 1995 (1) TC CA CA CA TC * CA *28 October 1995 (2) CA CA23 January 1996 (2) CA CA22 February 1996 (2) CA CA4 May 1996 (1) CA12, 19 June 1996 (1) CA7 July 1996 (1)2 August 1996 (1) CA24, 25 August 1996 (1) CA16 September 1996 (1) CA26 October 1996 (1) CA(1) air.(2) ground.TABLE 2. Biological and relocation information of Arctic char radio-tagged at the Hornaday River, 1999. Light gray area indicatesoverwintering period. Relocation areas: HM = Hornaday Mouth (east sideof estuary, shallow), BL = Bluffs (west side of estuary, deep), CA =Coalmine-Akluk (upper river).Tag site & date La Ronciere Falls: Hornaday River mouth:Fork length (mm) 29 July 1999 2-10 August 1999Fish no. 563 568 526 640 620 650 582 NA 22 23 24 25 26 27 28 29Survey date:1 October 1999 BL CA29 October 1999 BL HM CA BL BL CA14 November 1999 BL20 November 1999 BL