- Kobuk River
The Kobuk River is approximately convert|280|mi|km|0|lk=on long, located in the
Arcticregion of northwestern Alaskain the United States. [USGS Geographic Names Information System (GNIS). [http://geonames.usgs.gov/pls/gnispublic/f?p=gnispq:3:::NO::P3_FID:1413363 Kobuk River.] Accessed Aug 21, 2007.] Draining a basin with an area of 12,300 square miles (31850 km²) Brabets, T.P., Hydrologic Data and a Proposed Water-Quality Monitoring Network for the Kobuk River Basin, Gates of the Arctic National Park and Preserve, and Kobuk Valley National Park, Alaska. U.S. Geological Survey, Water Resources Investigations Report 01-4141, 2001] , the Kobuk River is among the largest rivers in northwest Alaska with widths of up to 1500 feet (460 m) and flow at a speed of 3-5 miles per hour (5-8 km per hour) in its lower and middle reaches Kobuk Valley National Park Final Environmental Impact Statement, National Park Service] . The Kobuk’s water is clear and carves meander scrolls, oxbow bends, and sloughs along its middle and lower course . The average elevation for the Kobuk River Basin is 1,300 feet above sea level (390 masl), ranging from near sea level to 11,400 feet (3,475 m) . Topography includes low, rolling mountains, plains and lowlands, moderately high rugged mountainous land, and some gently sloped plateaus and highlands .
It is commonly assumed that the Kobuk River issues from Walker Lake. However, the headwaters of the river are to the east of Walker Lake in the Endicott Mountains within the Gates of the Arctic National Park and Preserve, just north of the Arctic Circle near 67°05′N, 154°15′W. It flows briefly south, descending from the mountains through two spectacular canyons (Upper and Lower Kobuk Canyon), then flows generally west along the southern flank of the western Brooks Range in a broad wetlands valley. In the valley it passes a connected community of inland native villages, including Kobuk, Shungnak, and Ambler, where it receives the Ambler River. In the river’s lower reaches, where it passes between the Baird and Warring mountains, it traverses Kobuk Valley National Park, the location of the 25 square-mile (65 km²) Kobuk Sand Dunes. It then passes Kiana. The river enters its broad delta approximately 10 miles (16 km) southwest of Kiana. The delta is located in The Hotham Inlet of the Kotzebue Sound approximately 30 miles (48 km) southeast of Kotzebue.Alaska Planning Group, U.S. Department of the Interior. Final Environmental Statement for Proposed Kobuk Valley National Monument, 1973]
Inuitname means "big river". It was first transcribed by John Simpson in 1850 as "Kowuk." Explored by Lt. G. M. Stoney, USN, in 1883-1886, who wrote the name "Ku-buck," but proposed that it be called "Putnam" in honor of Master Charles Flint Putnam, USN, officer of the Rodgers, who was carried to sea on the ice and lost in 1880. Lt. J. C. Cantwell, USRCS, also explored the river in 1884 and 1885 and spelled the name "Koowak" on his map and "Kowak" in his text. Ivan Petroffspelled the river name "Kooak" in 1880, and W. H. Dall spelled it "Kowk" in 1870. Lt. H. T. Allen, USA, obtained the KoyukanIndian name in 1885 which he spelled "Holooatna" and "Holoatna."
Native peoples have hunted, fished, and lived along the Kobuk for at least 12,500 years and it has long been an important transportation route for inland peoples. In
1898the river was the scene of a brief gold rushcalled the Kobuk River Stampede. In 1980the United States Congressdesignated convert|110|mi|km|0 of the river downstream from Walker Lake as Kobuk Wild and Scenic River as part of the National Wild and Scenic Riverprogram. The river is considered an outstanding destination for recreational floating.
The river contains an exceptional population of sheefish ("Stenodus leucicthys"), a large predatory whitefish within the salmon family, found throughout the Arctic that spawns in the river's upper reaches during the autumn. [http://www.fishbase.org/Summary/SpeciesSummary.php?id=2692] , FishBase (April 2007)] A portion of the vast
Western Arctic Caribou Herdutilize the Kobuk river valley as winter range. [http://www.wildlife.alaska.gov/pubs/techpubs/mgt_rpts/ca03mt-wah.pdf] , Alaska Department of Fish and Game (December 2003)]
The Kobuk River Basin is located just north of the
ArcticCircle and has a continental climate. The summers are short and warm, while winters are long and cold. The mean annual temperature in the middle and upper portions of the Kobuk Valley is -6°C, and the mean temperature in July is 15°C Mann, D.H., Heiser, P.A., Finney, B.P, 2002. Holocene history of the Great Kobuk Sand Dunes, Northwestern Alaska. Quaternary Science Reviews, 21 (4-6). 709-731.] . An average of 21 inches (53 cm) of precipitation falls in the basin. However, actual precipitation can range from 15-40 inches (40-100 cm) with greater amounts falling in the upper reaches of the river basin .
The Kobuk River Basin is very sensitive to changes in climate. Arctic climates have warmed at approximately twice the global rate in the last several decades Anisimov, O.A., D.G. Vaughan, T.V. Callaghan, C. Furgal, H. Marchant, T.D. Prowse, H. Vilhjálmsson and J.E. Walsh, 2007: Polar regions (Arctic and Antarctic). Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F Canziani, J.P Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge, 653-685.] . Records of air-temperature from 1961-90 logged at the latitudes of the Kobuk River, show a warming trend of about 1.4°F (0.78°C) per decade . The warming has been the strongest in the winter and spring months . Observations of precipitation in the Arctic indicate an increase in precipitation by about 8% over the last 100 years ACIA, 2004: Impacts of a Warming Arctic: Arctic Climate Impact Assessment. Cambridge University Press, Cambridge, 23-33.] . Much of the increased precipitation has fallen as rain, mostly in winter months . In the North America Arctic, there has been an increase in the duration of snow-free days at the rate of 5-6 days per decade . Climate change is presently considered the most severe environmental stress in the Kobuk River Basin and throughout Alaska National Assessment Synthesis Team, Climate Change Impacts on the United States: The Potential Consequences of Climate Variability and Change, US Global Change Research Program, Washington DC, 2000] .
As a specific example, climate change will cause widespread thawing of permafrost in the discontinuous zone and significant changes in the continuous zone. Thawing permafrost can lead to a landscape of irregular depressions (thermokarst) due to subsiding soils. This can alter drainage patterns and even change the course of streams; whereas other areas could become swamplike. In addition, slope stability will decrease and permafrost degradation could lead to erosion of river banks resulting in an increase in sediment transport by the rivers Koster E.A. & M.E. Nieuwenhuijzen, 1992. Permafrost Response to Climatic Change. Published in Greenhouse-Impact on Cold-Climate Ecosystems and Landscapes, Editors: M. Boer & E. Koster.] . These physical changes will impact nutrient cycling and biological processes within the basin as well.
Geology and Soils
The Kobuk River is a periglacial river, fed by a remnant glacial lake (Walker Lake) and mountain snowmelt in the
Brooks Range. It cuts a channel through a landscape otherwise dominated by permafrost. The Kobuk’s current form and structure is a direct result of several stages of erosion and channel formation following the last glacial retreat.
As the glacier first retreated and melted, large amounts of highly erodible, fine-grained sediment dropped out in relatively high mountain valleys. The availability of fine-grained, loose sediment combined with a high gradient to turn a newly forming Kobuk River into a fast-working sediment transport system. The river picked up glacial till from its upper reaches and transported it downstream until the gradient diminished. When the river hit flatter ground, it deposited its sediment load resulting in the creation of large floodplains, alluvial fans, and meander bends through aggradation. Ballantyne, Colin K., Paraglacial Geomorphology. Quaternary Science Reviews 21 (2002), p. 1935 - 2017]
After the first stage of aggradation and sediment transport, the Kobuk began a new phase of erosion and landform development. The river exhausted its supply of easily erodible sediment upstream, thus decreasing its sediment load and increasing its downstream load carrying capacity. With more carrying capacity downstream, the river began to incise into the alluvial fan it previously created, moving sediment stored for a long time on its original floodplains to newer floodplains further downstream.
Further down in the Kobuk watershed, the river worked in concert with the wind to create one of the more famous landforms in Alaska: the Kobuk Dunes. These large sand dunes are the modern ancestor of alluvial deposits that became shaped and dominated by an exchange of aeolian and fluvial processes. Ashley, Gail and Hamilton, Thomas, Fluvial Response to Late Quaternary Climatic Fluctuations, Central Kobuk Valley, Northwestern Alaska. Journal of Sedimentary Petrology, Vol 63 No. 5, September 1993 pgs 814-827] In moister climates, the river has more water, and thus more power, and cuts down through a sandy bed. In times of drier climate, wind dominates and blows a lot of sediment into a weaker fluvial system, leading to aggradation and floodplain re-distribution.
Currently, the Kobuk River in its middle and lower reaches is an anastomizing stream, with several braided channels in places, wide migrating meander bends, and oxbow lakes. It is controlled by yearly cycles of freeze and thaw, much like its surrounding landscape. For six months of the year, the river is largely still, frozen on top by a thick layer of ice. In the spring, warmer temperatures cause this ice to begin to melt. But the resulting process is not gradual. Rather, the pressure of melting ice from upstream builds up upon ice “dams” in the river’s channel, eventually causing an “ice break-up” event, in which a flood of ice and water moves powerfully downstream.
These annual spring break-up events have several important consequences. First, the river has deeply undercut and eroded banks, caused by large, fast-moving chunks of ice carving out the river’s channel before it begins spilling out onto its floodplain, which is 1 to 6 miles (1.6-9.7 km) wide except at the confluence of major tributaries . Second, the river moves laterally very quickly and dramatically, re-inventing side channels every year as its secondary streams become drowned in each yearly flood by an overwhelming amount of sediment. Lastly, since the river is surrounded mostly by permafrost and because during the spring break-up event there are still large parts of frozen ground close to its banks, floods often transports large amounts of fine sediment across broad expanses of floodplain in thin sheets of water that slide easily across the frozen ground. These characteristics also translate into a relatively variable habitat for the Kobuk’s native species.
Farthest west, the Kobuk empties into Hotham Inlet, the easterly arm of Kotzebue Sound. During recent geologic times however, when sea level was lower, the Noatak, Kobuk, and Selawik Rivers were joined. Now they have separate deltas with many lakes and swamps and intricately webbed channel systems. The deltas are composed of silt, sand, and gravel .
Surface Water and Hydrology
The Kobuk River is ice covered 6 months of the year and in general, late October to late May is a period of relatively low flow . Annually, the hydrograph reflects two flood peaks: the first is associated with spring break-up and the second, a lesser peak, is associated with late summer precipitation . As the snowpack begins to melt toward the end of May, flow in the Kobuk River increases with most of the runoff occurring during June. Flow during the summer (July through September) is dominated by variable precipitation events .
Most of the major tributaries of the Kobuk River flow from the north drain the mountains in the southern Brooks Range. From east to west, these include the Reed River, Beaver Creek, Mauneluk River, Kogoluktuk River, Shungnak River, Ambler River, Akillik River, Tutuksuk River, Salmon River, and the Squirrel River Hydrologic Unit Map 1987 - U.S. Department of the Interior Geological Survey] . Within the Kobuk Valley National Park, are the Kallarichuk, Salmon, Tutuksuk, Kaliguricheark, Hunt, and Adillik rivers. All of their headwaters are in the Baird Mountains . The major tributaries flowing north from the Waring mountains are the Pah River, Pick River, and Niaktuvik Creek . The Pah River drains a lowland area of the basin. Most major tributaries draining high relief areas have higher unit runoff than tributaries draining the lower relief areas .
Walker Lake is at an altitude of 194 m in the "headwaters" of the Kobuk River Jones et al, Limnology of Walker Lake and Comparisons with Other Lakes in the Brooks Range, Alaska] . Other surface water features within the basin include Lake Selby, Nutuvukti Lake, and Norutak Lake . Additionally, numerous small lakes and ponds occur in the lowlands along the river, some formed as detached oxbows of the meandering river and others formed where permafrost has melted and caused depressions .
Flow records are available from USGS monitoring stations at Ambler (USGS 15744000) and Kiana (USGS 15744500). Average Annual Flow for the Kobuk River at Ambler has ranged from 5,839 cfs to 14,890 cfs over the period of record 1966-78, with peak discharge ranging from 30,000 cfs to 95,000 cfs. Near Kiana, Average Annual Flow has ranged from 10,020 cfs to 24,960 cfs for the period 1977-99 with peaks of 45,000 cfs to 161,000 cfs. Peak flows can result from large volumes of water released when ice jams fail . Flow records are also available for Dahl Creek, a tributary of the Kobuk River with a confluence near the town of Kobuk, from USGS (site number 15743850).
Primary production in arctic tundra streams
Walker Lakeand the Kobuk River, like other Arctic inland waters, are influenced primarily by vegetation of five different general types: 1) phytoplankton, 2)benthic algaes, 3)submerged bryophytes, 4)emergent vascular macrophytes, and 5)adjacent terrestrial plant assemblages. All plants in the Arctic are limited by low temperatures, a short growing season and often nutrients, particularly phosphorous. As a result, Arctic lakes, ponds and rivers tend to be oligotrophic. Most primary production occurs in adjacent terrestrial habitat, which may contribute leaf litter, particulate organic carbon, and exudates such as colored organic matter to nearby streams.
Phytoplankton is more prevalent in ponds and lakes because high residence time allows for accumulated biomass and higher production, whereas in rivers it is advected away from sources of production as “drift”. Common phytoplankters in Arctic lakes are
flagellatessuch as Rhodomonasand Chromulina, and diatoms. Both Walker Lake and the Kobuk are extremely oligotrophic due largely to phosphorous limitation. Production likely resembles open ocean food webswhere oligotrophic conditions select for nanoplanktonicorganisms that may have high numbers but very low biomass. Alexander, V., C.P. McRoy, R.J. Daley and D.W. Stanley. 1980. Ch. 5. Primary Producers. The Limnology of Tundra Ponds. J. E. Hobbe, ed., The Institute of Ecology] Jones, J.R., J.D. LaPerriere, and B.D. Perkins, , 1990. Limnology of Walker Lake and comparisons with other lakes in the Brooks Range, Alaska (USA). , 24, p.302-308]
Benthic algaes may occur growing within
sediments( epipelic) in aquatic soft-bottomed habitats or atop stones ( epilithic) in cobbled, hard-bottomed habitats. Benthic production is limited by water depth and turbidity, which can depress light intensity. Walker Lake and the Kobuk River tend to be unusually clear because of oligotrophic conditions and low turbidity due to the absence of glaciers. As a result, benthic algaes may be 60 times more abundant than planktonic in Arctic lakes and ponds, forming a large reservoir of primary production that may have some capacity to overwinter and thus accumulate on an interannual basis. Arscott, D.B., W.B. Bowden, J.C. Finlay. 1998. Comparison of epilithic algal and bryophyte metabolism in an arctic tundra stream, Alaska. J. N. Am. Benthol. Soc.17(2):210-227] However, high irradiance may also be photoinhibiting during summer and benthic production may be lower in most of Walker Lake due to its depth
Benthic epipelic (sediment growing) primary production is dominated by green and blue-green algaes. Turnover into the sediment limits production, so most of the algal biomass is confined to the top 1-2 cm of sediments. Epipelic algae is probably somewhat abundant in parts of Walker Lake and in the lowland valley stretches of the Kobuk River, and may be an important source of carbon for the food web.
Epilithic (stone growing) algae is dominated by diatoms, which would be expected to be somewhat prevalent in cobbled sections of the Kobuk River, limited mostly by
photoinhibition. Phosphorous may be less limiting than in Walker Lake due to edaphic inputs from surrounding tundra. Epilithic algae may form an important source of energy for secondary consumers in the form of aquatic insects. The dominant diatoms found in the nearby Kuparik Riverinclude " Cymbella minuta", " Achnanthes minutissima", " Hannea arcus", and " Diatoma tenue" var. elongatum] MILLER, M. C., P. DEOLIVEIRA, AND G. G. GIBEAU. 1992. Epilithic diatom community response to years of P04 fertilization: Kuparuk River, Alaska (68N Lat.). Hydrobiologia 240:103-119.]
Mossesare dominated by " Schistidium agassizii" although experiments on the Kuparuk River show that Hygrohypnumspp. may become abundant with phosphorus fertilization. The two mosses appear to carve out niche space through trade-offs in competitive ability under variable conditions . Bryophytes in general may form an important supply of carbon to aquatic invertebrates because of their rapid uptake of nutrients, resistance to low light and temperature, and resistance to scouring Bowden, W. B., J. C. Finlay, And P. E. Maloney. 1994. Long-term effects of P04 fertilization on the distribution of bryophytes in an arctic river. Freshwater Biology 32:445-454.] FINLAY, J. C., AND W. B. BOWDEN. 1994. Controls on production of bryophytes in an arctic tundra stream. Freshwater Biology 32:455-466.] . In general, the contributions of bryophytes to stream ecology is less well understood than other forms of primary production such as epipelic and epilithic algae STREAM BRYOPHYTE GROUP. J. N. Am. Benthol. Soc., 1999, 18(2):151-184 Roles of bryophytes in stream ecosystems ]
Emergent vascular macrophytes
Rooted aquatic plants are represented by
sedgessuch as " Carex aquatilis", grasses such as " Arctophila fulva", and the buttercup " Ranunculus pallasii". These plants generally propagate vegetatively via rhizomesbecause of the short growing season and harsh conditions, re-directing energy from sexual reproduction into vegetative growth.
Of these, "C. aquatilis" is the dominant in slow waters, lakes and ponds. Most of the biomass of the plant lives below ground while only the basal part of the stem survives the winter. The lifetime production of a plant is about 20-25 leaves in 4-7 years, and overall production is thought to be higher than in terrestrial tundra plants because of freezing protection afforded to organisms in the aquatic environment, and because dead leaf attachments that may shade the plant are removed by water and decomposition .
Adjacent terrestrial and wetland vascular macrophytes
Adjacent ecosystems may contribute to aquatic production through leaf litter for aquatic invertebrates, dissolved organic carbon for bacterial and rotifer production, or fixed nitrogen to support aquatic primary production. These plant assemblages include 1)
moist tundra(in river valley lowlands), 2) boreal forest(up to 2100’), 3) shrub thickets(up to 3000’), and 4) alpine tundra(above 3000’). Tundra tends to dominate the Kobuk River, punctuated by stands of boreal forest and shrub thicket.
1) Moist tundra occurs in moderately drained soils in river valley. It is dominated by
cottongrasstussocks, with moss and lichensgrowing in the moist channels between the tussocks. Cottongrass dies each year, allowing dead leaves to accumulate, forming the tussock topography of the tundra. Also found in this habitat are small shrubs such as dwarf birch, willowand Labrador tea; grasses; and annual herbs and flowers.
2) Boreal forest, also known as
taiga, consists of sprucestands mixed with hardwoods that follow Arctic river valleys. There are two forms of boreal forest on the Kobuk, associated with southern or northern slopes.
Southern slopes are dominated by
white spruceassociated birch, aspenor balsam poplarhardwoods. Ground cover may be characterized by heaths of bearberry, crowberry, Labrador tea, blueberry, cranberryand arctic willow. Lichens and mosses may also be found on the substrate.
Northern facing slopes and poorly drained valleys are dominated by
black spruce, with an understory of spongy moss and low brush. The spruce may grow very slowly, such that a two inch diameter tree may be one hundred years old; trees are often stunted and scattered.
3) Shrub thickets are characterized also by at least two somewhat different plant assemblages, determined by elevation and hydrology.
Lowland shrub thickets are found on
alluvialplains and gravel bars of low-incline, meandering streams. Low-lying willow and alder dominate, interspersed with dwarf fireweed, horsetail, prickly rose, and annual flowers. These communities grow rapidly on floodplainsthat are disturbed regularly by ice breakup and spring floods.
Alpine shrub thickets are found at higher elevations and give way to alpine tundra above about 3000’. At drier sites dwarf and
resin birchdominate; while at wetter sites willow and alder dominate, interspersed by reindeer lichens, heaths, and other alpine tundra plants.
4) Alpine tundra occurs at higher elevations, in well drained, coarse, rocky soils. It is characterized by mat-forming heathers,
moss campion, saxifrage, and reindeer lichen, as well as sedges, grasses, herbs and wildflowers.
Fires structure these plant communities episodically. Pioneer species include fireweed, Labrador tea, willow, and alders. Secondary successional species include
quaking aspen(south facing slopes), paper birch (east or west slopes), and balsam poplars on river plains. Late successional assemblages include white- or black spruce-associated boreal forest species and reindeer lichens.
This is a list of common moist tundra species, a community that can be expected to characterize much of the Kobuk River valley:willow ("
dwarf birch ("
Labrador tea ("
Ledum" spp.) Lapland rosebay(" Rhododendron lapponicum") mountain alder(" Alnus crispa") mountain avens(" Dryas" spp.)
arrow grass(" Triglochin" spp.) pendant grass(" Arctophyla fulva") bog rosemary(" Andromeda polifolia") louseworts(" Pedicularis" spp.) rushes(" Juncus" spp.).
Plant list link here for the Gates of the Arctic National Park: [http://endeavor.des.ucdavis.edu/nps/species.asp?park=USANOAT0B&taxa=Plant]
Secondary productionin Arctic inland waters is distinctly different from that in temperate or tropical fresh water systems. Limited primary production because of thermal, light or nutrient limitation leads to an oligotrophicsystem. Foodwebs tend to resemble open ocean foodwebs, weighted at the lower levels with very small organisms, requiring many steps , and having many individuals with very low biomass. Primary production supplies mainly ciliates, rotifers, copepods, cladoceransor aquatic insects. Secondary production provides food for predatory copepods, fairy shrimp( Anostraca), and to a lesser degree predatory aquatic insects (which appear to be rare in the Arctic). Aquatic insects, copepods, and fairy shrimp all may supply larval fish [Dodson, Stanley I. 1975. Predation Rates of Zooplankton in Arctic Ponds. Limnology and Oceanography 20(3):426-433] . Secondary production derives from three main sources: 1) phytoplankton from water bodies with high residence time, such as Walker Lake, or oxbow ponds in the lower Kobuk River Valley; 2) benthic algae and bryophytes, which persist in shallow waters in both Walker Lake and the Kobuk River main stem; and 3) adjacent terrestrial plant communities.
Secondary production from phytoplankton
Planktonic foodwebs rely on waters with high
residence time, so most input of plankton derives from Walker Lake, some of which may appear in the upper Kobuk River as “drift”. Phytoplanktonis consumed largely by daphnia, which may comprise up to 80% of zooplanktonfound in Arctic ponds. In fishless ponds, larger species of copepods tend to dominate. In ponds with fishes, smaller species make up most of the zooplankton as they are probably less vulnerable to predation. [Nilsson, N.A., B. Pejler. 1973. On the Relation Between Fish Fauna and Zooplankton Composition in North Swedish Lakes. Inst Freshwater Res Drottningholm Rep. 53:51-77] Zooplankton production is also controlled by low temperatures, low primary production and the short growing season. Species have generally adapted to these constraints by producing just one generation per year, which overwinters by producing diapausal eggs or embryos. Stross R.G., M.C. Miller, R.J. Daley. 1980. Ch. 6. Zooplankton in Limnology of Tundra Ponds, John E Hobbe, ed. pp 251-296]
econdary production deriving from benthos
While plankton has been considered centrally important to Arctic lake ecosystems such as Walker Lake and in the Kobuk River, oligotrophic conditions leave the zooplankton largely depauperate. However, nutrient limitation is not as severe on the benthos, due largely to the accumulation of phosphate there. Growth of epilithon and epipelon are fueled by green and blue-green algaes which support populations of bacteria, ciliates and rotifers,; these films, in conjunction with bryophytes and leaf drop, support aquatic insects, cladocerans such as "
Eurycercus lamellatu" [Miller, Michael C. & James R. Stout. 1989. Variability of macroinvertebrate community composition in an arctic and subarctic stream. Hydrobiologia 172:111-127] and possibly, snails, which are fed upon directly by fishes. [Sierszen, Michael E., Michael E. McDonald and Douglas A. Jensen. 2003. Benthos as the basis for arctic lake food webs. Aquatic Ecology 37:437–445]
In addition to benthic algaes, bryophytes provide a source of production through both direct and indirect (facilitative) ways. Bryophytes support populations of aquatic insects which graze directly on their tissue, but they also facilitate the growth of epiphytic algaes and as collectors for fine particulate organic matter, which promotes bacterial decomposition and the formation of epipelon, also an important source of grazing for aquatic insects.
econdary production deriving from adjacent terrestrial plant communities
Plant primary production that is biologically available to the aquatic system is in the form of leaf production [Shaver, Gaius R. and F. Stuart Chapin III. 1991. Biomass Relationships and Element Cycling in Contrasting Arctic Vegetation Types. Ecological Monographs 61(1):1-31] or in the form of dissolved organic carbon. Both are important in Arctic systems because limited in-stream production (due to oligotrophic conditions) causes terrestrial inputs to become relatively more important. In addition, the low rates of decomposition relative to primary production found in the Arctic have created a thick organic layer; up to 13% of the world’s soil C is stored in Arctic soils. This high reserve of C creates an important terrestrial-water link not typically found in other ecosystems. [Judd, Kristin E. and George W. Kling. 2002. Production and Export of Dissolved C in Arctic Tundra Mesocosms: The Roles of Vegetation and Water Flow. Biogeochemistry 60(3):213-234] Particulate matter that is washed into adjacent streams can accumulate in the benthos (as with bryophytes), forming an important source of epipelon.
Peat from adjacent plant communities may also be a large source of dissolved organic carbon, which may be used by bacteria and consumed by aquatic filter-feeders, such as dipterid larvae. [Hershey, A.E., Merritt, R.W. & Miller, M.C., 1995. Insect diversity, life history, and trophic dynamics in Arctic streams, with particular emphasis on black flies (Diptera: Simuliidae). Arctic and alpine biodiversity. Edited by FS Chapin, III, and C. Körner. Springer, Berlin, 283–296]
macroinvertebratecommunity of the Kobuk River provides a critical resource to several higher order trophic level consumers from both aquatic and terrestrial habitats including predatory fish, mammals, and birds. The macroinvertebrate assemblage, largely dictated by the unique environmental conditions, disturbance regimes, food availability, and habitat features of the Kobuk River drainage, is less diverse than similar sized temperate region rivers and dominated by a few families of aquatic Diptera. There are several reasons for this apparent discrepancy in invertebrate fauna diversity including routine localized disturbances such as freezing of the water column, variable seasonal discharge during spring melt, scouring of the river bed surface through the release of anchor iceand seasonal food availability; all of which may adversely affect the survival rates of most aquatic macroinvertebrates in the region. Miller, M.C., and Stout, J.R. 1989. Variability of macroinvertebrate community composition in an arctic and subarctic stream. Hydrobiologia, 172: 111-127.]
The Kobuk River dipteran community are largely composed of
Chironomidae(non-biting midges), Ceratopogonidae(biting midges), and to a lesser extent, Simuliidae(black flies) and Empididae(dagger flies). Primary productivityon the Kobuk River, similar to many high Arctic rivers, is largely composed of fine particulate organic matter (from the direct leaching of peat) and the dipterans (especially the chironomid midges) seem particularly suited to capitalize on this important carbon source due to their functional feeding adaptations. [Hershey, A.E., Merritt, R.W., and Miller, M.C. 1995. Insect diversity, life history, and trophic dynamics in arctic streams, with particular emphasis on black flies (Diptera: Simuliidae). In Arctic and alpine biodiversity: patterns, causes, and ecosystem consequences. Edited by F.S. Chapin III and C. Korner. Ecological Studies Vol. 113. Springer-Verlag, Berlin, Heidelberg. Pp. 283-295.] Specifically, these types of species acquire the majority of their food resources through direct filtering and collection of minute food particles suspended in the water column, although some are predators. Due to minimal coarse particulate organic matter and other sources and nutrients, it appears that the filter feeding/collector and highly tolerant dipterans are uniquely situated to dominate the aquatic invertebrate community of the Kobuk River. In addition, these families and others show several ecological and physiological adaptations allowing them to persist under the harsh Arctic environmental conditions.Danks, H.V. 2007. How aquatic insects live in cold climates. Canadian Entomology, 139: 443-471.]
Those species able to survive through the Arctic winter on the Kobuk River are primarily
univoltine, exhibit a long life cycle which may exceed an entire year, experience periods of dormancy, and may use particular advantageous physiological adaptations to endure the cold winter months. Because development is difficult and slow paced under climatic extremes such as the Arctic, most aquatic invertebrate species are only able to produce one generation per year and the lifecycle duration of many species may range over a several year period before adult emergence. Several Arctic aquatic invertebrate species (most notably those of the Chironomidae family) have been shown to tolerate freezing during the winter [Olsson, T.I. 1981. Overwintering of benthic macroinvertebrates in ice and frozen sediment in a north Swedish river. Holarctic Ecology, 4: 161-166.] , either through larval dehydration or by creating specific proteins which protect the internal cavity of the species. Other successful adaptations by Arctic macroinvertebrates include drifting to more thermally favorable habitat, over-wintering larval eggs, and dormancy or diapause. Plecoptera(stoneflies), Ephemeroptera(mayflies), and Trichoptera(caddisflies) also make up a portion of the Kobuk River macroinvertebrate assemblage, but to a much lesser extent than the dipterans. The lack of diversity and abundance of species from these orders may largely be dictated by the available food resources present within the Kobuk drainage at any one time and/or an inability to adapt to extremely severe winter conditions. The family Nemouridaelikely represent a significant proportion of the stonefly order, while the Baetidaeand Heptageniidaerepresent the dominant mayfly families. Tricopterans are even more sparsely populated and may be restricted to particular microhabitats especially higher up in the watershed. Finally, several orders of insects rarely make an appearance on the Kobuk River, including the Hemiptera, Odonata, Megaloptera, and Coleoptera. [Oswood, M.W. 1989. Community Structure of benthic invertebrates in interior Alaska (USA) streams and rivers. Hydrobiologia, 172: 97-110.]
The Kobuk River drainage contains at least 18 species of fish along the roughly 450 km of main stem and thousands of streams, lakes, ponds and sloughs. All the species are native and none are listed as threatened or endangered. Fishing is an important part of the native culture in the Kobuk River and fish often constitute the main part of the diet (e.g. Georgette, S. and A. Shiedt. 2005. Whitefish: Traditional Ecological Knowledge and Subsistence Fishing in the Kotzebue Sound Region, Alaska. Alaska Department of Fish and Game. Technical paper No. 290. Kotzebue, Alaska.] ). Fish comprises more than half of the subsistence harvest in many households on the Kobuk River and an average of 104.3 kilograms (230 pounds) of fish per person are consumed annually in rural Alaska. USFWS 2006. U.S. Fish and Wildlife Service website, Fairbanks, Alaska http://cybersalmon.fws.gov. Last updated Jan 18, 2006.]
Walker Lake is a large glacial lake located close to the headwaters of the Kobuk River approximately 400 km upstream from Hotlam Inlet. The lake contains a variety of fish species: whitefishes, chars, northern pike, longonse sucker, burbot, slimy sculpin and ninespine stickleblack, among others There are many other lakes in the Kobuk River drainage that, in some cases, contain similar assemblages and provide essential overwintering and feeding areas to the fish of the Kobuk River. The river supports many migratory populations of whitefish, and to a lesser degree chum salmon and, Dolly Varden, whose abundances are seasonal. Some species are permanently present in the main stem, such as Alaska blackfish, which is well adapted to the severe winter conditions of the Arctic Kobuk River. The lower floodplains of the Kobuk River, especially close to the Kobuk River delta, contain many shallow lakes and sloughs that create a high diversity of habitats normally used for feeding and overwintering. Adams, F. J. 1990. Population characteristics of lake trout in Walker Lake, Gates of the Arctic National Park and Preserve, Alaska. MS thesis, University of Alaska Fairbanks.] ADF&G 2008. Alaska Department of Fish and Game website. http://www.cf.adfg.state.ak.us Last updated May 1, 2008.] USNPS 2008. U.S. National Park Service, Kobuk Valley, Alaska. http://www.nps.gov/kova. Last updated April 15 2008.]
The order salmoniformes has the highest richness among the Kobuk species, which is typical of Arctic freshwater ecosystems. The families present are Salmonidae (with three subfamilies: Coregoninae, Salmoninae and Thymallinae), Esocidae, Lotidae, Dalliidae, Catostomidae, Cottidae and Gasterosteidae (Table 1). The subfamilies Coregoninae and Salmoninae are the most significant in the Kobuk River with at least six and five species respectively. All other families have only one species represented.
Table 1. Families and species of fish represented in the Kobuk River. Alt, K.T. 1969. Taxonomy and ecology of the inconnu stenodus-leucichthys-nelma in alaska. biological papers of the university of Alaska no 12, pp. 1-53.]
The following descriptions refer to the biology of each fish species, with emphasis on the Kobuk River ecosystem.
Sheefish("Stendous leucichthys"), also called Inconnu(unknown fish), are large piscivorous and of the whitefish family. They grow slowly and reach up to 27 kg in the Kobuk River. The northernmost range limit of sheefish in Alaska occurs in the lower reaches of the Noatak River. There, the fish only feed, and spawning occurs in the more southern Kobuk River. Sheefish in the Kobuk River, Selawik River, and Kotzebue Sound constitute one single population. Feeding and wintering grounds of this population are in the lower reaches of the Kobuk River, Hotham Inlet, and Selawik River drainage Alt, K.T. 1977. Inventory and cataloging of sportfish and sportfish waters of western Alaska. Federal Aid in Fisheries Restoration, Annual Report of Progress, 1976-1977. Project G-1-P, R II. Alaska Department of Fish and Game, Sportfish Division, Juneau, Alaska.]
In the spring before the ice breaks up, the sheefish start the slow upstream migration in the Kobuk River; both mature and immature fish start the migration together. They usually do not enter the tributaries of the Kobuk River. Instead, the fish move to the feeding grounds of the lower reaches of the Kobuk for about one month, and then spawners migrate to spawning grounds, most of which can be found in the area between the Kobuk Village and the Reed River during summer and fall. Sheefish have been reported as far upstream as the Lower Kobuk Canyon, where rapids and falls seem to block their upstream migration. The optimum riverbed composition is differentially sized coarse gravel, with no silt and some sand. Major spawning grounds seem to be located between 38 and 48 km above the Kobuk Village where depths vary from approximately 1 to 3 meters. Females spawn on the surface of the water and then the males fertilize the eggs. Spawning usually occurs in the afternoon and evening. Non spawning fish stay in the feeding grounds not far from the mouth of the Kobuk River for the rest of the summer. It is not certain if they spawn every year or alternates years. Other immature sheefish summer in Kotzebue Sound and Hotlam Inlet, among other areas.
After spawning, they undertake a rapid migration to areas close to Noorvik and Kiana. They may feed for a short period of time before migrating slowly to the overwintering areas of the lower Kobuk River and/or slightly brackish water of the Hotham Inlet and Selawik Lake (Alt 1977). The young migrate downstream with the spring floods where the early years of life are spent. Sheefish younger than 4 years old are not normally found in the upper reaches of the Kobuk River. They rarely feed while migrating to the spawning grounds, although they are still in good condition when they reach the grounds in late September. Morrow, J. 1980. The Freshwater Fishes of Alaska. University of British Columbia Resource Ecology Library: University of British Columbia. ] The diet varies according to size, age and season. The young start feeding on plankton, but soon prey upon insect larvae and zooplankton. Important in the adult diet are isopods, Mysis and other whitefishes, char, smelt, blackfish, suckers, burbot, sticklebacks and sculpins which are abundant in the Kobuk River drainage.
Most subsistence fishing occurs in late August and September, although native people prefer to harvest them late in the season because they have higher fat content, the eggs are ripe, and sheefish can be aged and frozen which is a more preferable method than drying. Three types of gear are usually used for fishing; gill nets, beach seines, and rods and reels. Georgette S. and H. Loon. 1990. Subsistence and sport fishing of sheefish on the upper Kobuk River, Alaska. Alaska Department of Fish and Game. Technical paper No. 175, Kotzebue, Alaska.]
Broad whitefish ("Coregonus nasus") are called the Kobuk River fish because they are more abundant in the Kobuk River than in other rivers of the region, but not in such large numbers as some of its relatives. They are the largest whitefish in the Kobuk River after sheefish, have a high fat content, and are an important species for the subsistence of the native people . They grow slowly and the largest broad whitefish recorded in Alaska measured 67 cm. Alt, K. T., and D. R. Kogl. 1973. Notes on the whitefish of the Coville River, Alaska. Journal Fisheries Research Board of Canada 30: 554-556.] This species has a variety of ecological forms in the Kobuk River system, and are seasonally present in most of the available habitats (Table 2) . Some fish overwinter in Hotlam Inlet and Selawik Lake, others in the main stem of the Kobuk River and delta, and others in the deep lakes that are found along the river. In spring, when the ice breaks up, the broad whitefish search for the most productive feeding areas before spawning in a very complex movement pattern. Some move into the lower reaches of the Kobuk River and delta; others move out of the lakes into the streams, main stem and/or to other lakes and sloughs; others move into the tundra and floodplain lakes; others migrate to the upper reaches in search of other lakes, and others spend the summer in Hotlam-Selawik estuary, coastal lagoons and other rivers.
Most undertake the upstream spawning migration from as early as June until September and actual spawning takes place from September to November. They are the last whitefish in the Kobuk River to spawn. After spawning, they migrate back to their overwintering areas, which are mainly located in lakes or the lower reaches of the Kobuk River delta and Hotlam Inlet. Spawning takes place on gravel bottoms, where the young emerge the following spring and most move downstream. They are bottom feeders, eating zooplankton when young, and chironomid, mosquito larvae, and crustaceans as adults.
Table 2. Summary of the main seasonal locations of broad whitefish in the Kobuk River drainage.
Humpback whitefish ("Coregonus pidschian") occur in at least two ecological forms in the Kobuk River drainage: diadromous and resident. The diadromous start migrating from the lower reaches of the Kobuk River drainage in June and spawn in the upper reaches in October. The young emerge in late winter and spring and migrate downstream to the lower reaches of the river and the estuary. They return after 4 to 6 years when they are sexually mature. The resident fish move from lakes to the main stem, tributaries or other lakes along the Kobuk River in spring and feed throughout the summer . They spawn generally in the upper reaches of Kobuk River and then return to the lakes to overwinter. The young mainly feed on zooplankton, while the adult’s diet consists of crustaceans and chironomid larvae. They grow slowly; a 5+ year old fish measure approximately 26 cm, and a 10 year old fish 40 cm. They are harvested in great numbers and are the primary food source for most of the villages along the river .
Round whitefish("Prosopium cylindraceum") are the only whitefish of the genus Prosopium in the Kobuk River, and are generally found in freshwater. They are more abundant in the upper Kobuk River than in the lower reaches downstream from Noorvik. They are present in smaller numbers than the other whitefishes and the maximum weight in the drainage is up to two kg. Spawning migrations to the shallow gravel grounds of the upper reaches occurs from late September to October, although they can spawn on the inshore of the lakes . They grow slowly, reaching sexual maturity after approximately 7 years and measuring about 50 cm at 12 years in the Kobuk River. They primarily feed on the immature stages of insects and other invertebrates . Finally, the Round whitefish is not regarded as valuable by native people because it is said to taste like “the metal of a wet knife” .
Least cisco ("Coregonus sardinella") are the smallest and potentially the most abundant whitefish in the Kobuk River, although their migration patterns cause abundances to change seasonally. Least cisco overwinter in the lower reaches of the Kobuk River and also reaches the brackish waters of Hotlam Inlet and Selawik Lake. The species have been observed as far inland as Walker Lake. Least cisco move into lakes to feed soon after the ice breaks up and spend the summer feeding in lakes . In the fall, fish move out of the lakes to the main Kobuk River to spawn. The spawning substrate is composed of gravel and sand, and it appears that least cisco find these substrates in reaches downstream from Shungnak. They spawn from late September to early October at night and normally do not feed during the spawning run. The eggs can be found in a variety of colors: orange, pink, white and yellow. The eggs and the eyes of the fish are very appreciated by the native people. The eggs winter in the gravel and hatch early in the spring; the young migrate downstream to deeper, slower waters. They feed on diverse types of zooplankton, "
Mysis relicta", insect larvae, and also plant material. Many predators feed on the eggs, including eagles, pike, sheefish, lake trout, burbot and humans.
Bering Cisco ("Coregonus laurettae") is mainly found in the Hotlam Inlet and its lagoons, although it may be present in reduced numbers in the lower reaches and delta of the Kobuk River.
Chum salmon("Oncorhynchus keta") undertake moderate runs in the Kobuk River during the summer along with a few individuals of pink salmon. (Oncorhynchus gorbuscha) Menard J. and S. Kent. 2006. Kobuk River Test Fishing Project 2006. Alaska Department of Fish and Game. Fishery Data Series No. 06-05, Anchorage.] Chum have been observed as far inland as Walker Lake Subsistence fisheries target this species in the Kobuk River when salmon migrate upstream from late June through early September, and they make up to approximately 10% of the total food source in the households of the Kobuk River. Young emerge the following spring and migrate directly to the sea. They usually remain at sea from two to four years before returning as adults to spawn. Bulkis. L. S. 1994. Chum salmon. Wildlife Notebook Series, Alaska Department of Fish and Game. http://www.adfg.state.ak.us/pubs/notebook. Last updated Nov 28, 2007.] Lake trout("Salvelinus namaycush") are the largest freshwater fish in Alaska. Bendock T. 1994. Lake trout. Wildlife Notebook Series, Alaska Department of Fish and Game. http://www.adfg.state.ak.us/pubs/notebook. Last updated Nov 28, 2007.] Lake trout are char with a limited distribution to a few deeper headwater lakes in the upper Kobuk River, such as Walker Lake and Selby Lake. Burr. J. B. 1993. Maturity of Lake Trout from Eleven Lakes in Alaska. Northwest Science, 67: 78-87.] They usually inhabit large, deep, cold lakes where they can complete their life cycle. Spawning usually occurs on the rocky and clean bottoms of lakes from late August through late November. Kobuk natives have observed a few lake trout spawning in the main stem of the river. The spawning frequency for females in Walker Lake is once every two years and the youngest age at maturity is 12 years for both males and females. Lake trout in Walker Lake grow slowly, and lengths range from approximately 200 to 900 mm and 80 to 8500 g. The oldest ever aged was 26 years. The diet varies according to age, size, locality, and available food, such as zooplankton, insects, fishes, algae and worms. Mature trout feed almost exclusively on fish when available and in the Kobuk lakes they may feed upon whitefish, grayling, sticklebacks, sculpins and suckers, among others. Arctic char("Salvelinus alpinus") occur in its resident form in Walker Lake, Selby Lake and other lakes in the middle and upper Kobuk River. Artic char. Wildlife Notebook Series, Alaska Department of Fish and Game. http://www.adfg.state.ak.us/pubs/notebook. Last updated Nov 28, 2007.] Arctic char spawn every other year after reaching sexual maturity at 6 to 9 years. Spawning occurs mainly in lakes from August through October on gravel bottoms at sufficient depth to be protected from winter ice. These fish grow slowly, , and weights over 10 pounds are not uncommon in some Alaska lakes. Artic char are opportunistic feeders; they prey on fish, crustaceans, worms and macroinvertebrates.
Dolly Varden ("Salvelinus malma") are char found in the Kobuk River system. In Northern Alaska, they occur in lake resident, stream resident, and anadromous forms. They may occur in all of these possible forms in the Kobuk River drainage, but this has not been studied. They spawn in streams, usually from mid-August to November Hubartt D. 1994. Dolly Varden. Wildlife Notebook Series, Alaska Department of Fish and Game. http://www.adfg.state.ak.us/pubs/notebook. Last updated Nov 28, 2007.] and have been observed while spawning in several Kobuk River tributaries. The optimum substrate is mainly composed of gravel in which the eggs overwinter. After hatching the following spring, the young rear in streams from three to four years before their first migration to sea. Once at sea, they begin a complex pattern of migration, wintering in and migrating to and from fresh water. In the Arctic, young and adults winter in springs and spring-fed areas of streams, and the adults go to sea to feed every year immediately after the ice breaks up. Mature spawners normally migrate back from the sea to their natal stream in August; in contrast, the non spawners return later and not necessarily to their natal stream. The diet varies according to age and size of the fish, locality, and the available food; young feed mainly on insects and crustaceans, and adults incorporate fish, fish eggs and worms into their diets. The fishery in the Kobuk River is of lesser importance compared to that of the Noatak where thousands of migratory Dolly Varden overwinter in the lower part of the river.
Arctic grayling("Thymallus arcticus") are ubiquitous in the Kobuk River from the lower reaches to Walker Lake. They are considered one of the most beautiful fish in Alaska due to a sail-like dorsal fin with purple and red spots. Holmes R. 1994. Artic grayling. Wildlife Notebook Series, Alaska Department of Fish and Game. http://www.adfg.state.ak.us/pubs/notebook. Last updated Nov 28, 2007.] They are freshwater residents in the main Kobuk River, tributaries and lakes, and migrate among habitats for spawning in the spring, feeding during the summer and overwintering. They are even able to complete their life cycle in short river sections or in a lake without the need for migration. They probably spend the winter in the deeper lakes and pools of the main stem. Their tolerance to low dissolved oxygen allows them to survive in places where other salmonids would die due to the severity of the long Arctic winters. In spring, they usually start the upstream migration to the same spawning sites. After spawning, they move to the feeding areas. Fry emerge in approximately three weeks and generally start the overwintering migration to the downstream reaches in the early fall. They are omnivorous but they prefer aquatic insects, fish eggs and occasionally small fish. They are important for the subsistence fisheries in the Kobuk River. A popular harvest method consists of setting up gill nets at the mouth of the small streams draining from lake systems in the spring after the ice breaks up . Northern pike("Esox lucius") occur seasonally in many of the lakes, streams, sloughs and main stem of the Kobuk River drainage Alt, K.T. 1994. Northern pike. Wildlife Notebook Series, Alaska Department of Fish and Game. Revised and reprinted 1994. http://www.adfg.state.ak.us/pubs/notebook. Last updated Nov 28, 2007.] Northern pike in the Kobuk River weigh up to 10 pounds, but in Alaska can reach 20 pounds. Spawning occurs in spring soon after the ice melts; eggs are laid in the grassy shores of lakes, streams or probably in the slow areas of the main Kobuk River. Incubation takes around 30 days in Alaska and emerging fry feed on insects and small crustaceans. The diet of adult pike is mainly composed of fish and occasionally other aquatic and terrestrial animals. In spring, they migrate from the overwintering areas to spawn, and later, to feeding grounds for the summer. The fisheries are quite important for the households of the Kobuk River villages, who harvest them in spring when they leave the lakes after the ice breaks up. They also catch pike during the winter in deep areas of the Kobuk River . Burbot("Lota lota") are nocturnal, voracious bottom feeders Chen, L.C. 1969. The biology and taxonomy of the burbot, Lota lota leptura, in interior Alaska. Biological Papers of the University of Alaska, No 11, pp. 1–53.] which inhabit probably the deepest waters of the Kobuk River system. They have been reported in the main stem, and Walker Lake and may be present in most of deep lakes along the Kobuk River and its brackish estuary. Burbot grow slowly and are long lived; burbot older than 20 years are common in Alaska Holmes R. 1994. Burbot. Wildlife Notebook Series, Alaska Department of Fish and Game. http://www.adfg.state.ak.us/pubs/notebook. Last updated Nov 28, 2007.] They spawn under the ice during the winter and mill together forming a ball while spawning. Spawning occurs in lakes and rivers; sedentary fish do not undertake important spawning or feeding migrations. They move to shallow waters to spawn on sand, gravel or cobble grounds. Young feed mainly on invertebrates, and adults prey almost exclusively on fish (whitefish, sculpins, suckers, pike, among others). Alaska blackfish("Dallia pectoralis") are small freshwater fish which rarely exceed 20 cm in length. They are well adapted to the harsh conditions of the Artic with the ability to survive at low levels of oxygen, partial freezing and they have the capacity to breathe atmospheric oxygen. Armstrong R. H. 1994. Alaska blackfish. Wildlife Notebook Series, Alaska Department of Fish and Game. http://www.adfg.state.ak.us/pubs/notebook. Last updated Nov 28, 2007.] Alaska blackfish probably occur in most habitats of the Kobuk River system due to their ability to thrive in any conditions. They are sluggish bottom feeders that may be abundant in the tundra and floodplain lakes and sloughs of the main stem. They can survive in stagnant tundra pools, swamps and shallow lakes during the summer where vegetation can be abundant. Spawning occurs during the spring and summer and their fertilized eggs adhere to aquatic vegetation because they are demersal and sticky. Hatching occurs in about 10 days when water temperatures are approximately 12 to 13 degrees Celsius. The young are about 6 mm at hatching and their yolk sacs last for about ten days. Small individuals eat mostly copepods and Cladocera, shifting as they grow larger to insect larvae, snails, and more rarely small fishes. They are preyed upon by many terrestrial and aquatic animals. The fisheries can be very important in the Artic when the other food supplies are less available or consumed in the late winter. Longnose sucker("Catostomous catostomus") is the only sucker located in Alaska. Mansfield K. 2004. Longnose sucker. Wildlife Notebook Series, Alaska Department of Fish and Game. http://www.adfg.state.ak.us/pubs/notebook. Last updated Nov 28, 2007.] They are present in the Kobuk River system and have been found as far inland as Walker Lake.