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HomeMy WebLinkAboutAPA3334SUSITNA HYDROELECTRIC PROJECT -I FEDERAL ENERGY'REGULATORY COMMISSION PROJECT No.7114 Alaska Power Authority -i, ~2%£=g@3£®©@ IrNA JOINT VENTURE FURBEARER STUDIES FALL 1985:BEAVER FINAL REPORT MARCH 1986 DOCUMENT No.3334 -, ..... SUSITNA HYDROELECTRIC PROJECT FURBEARER STUDIES FALL 1985:BEAVER Report by LGL Alaska Research Associates,Inc. James D.Woolington and Harza-Ebasco Susitna Joint Venture Prepared for Alaska Power Authority Document No.3334 Susitna File No.4.3.3.2 TIC /li;2 5 .s '6 F8}~ 010 3?>j,Lt .- Final Report March 1986 ARLIS Alaska Resources Library &InformatIOn ServIces Anchorage,Alaska - - - - - NOTICE ANY QUESTIONS OR COMMENTS CONCERNING THIS REPORT SHOULD BE DIRECTED TO THE ALASKA POWER AUTHORITY SUSITNA PROJECT OFFICE ARLIS Alaska Resources Library &InformatIOn ServIces Anchorage,Alaska .- - -I Int:roduc tion Bea'ller (Castor canadensis)is a visible,easily-studied species tied directly to both aquatic and terrestrial ecosystems.As such,it is the only furbearer species being studied on an ongoing basis as part of the Susitna Hydroe lectric Project licensing proces s.Studies of beaver of the Susitna River between the Deshka (RM 40)and Tyone (RM 147)Rivers have been conducted since 1980,with the majority of work along the floodplain of the middle Susitna River (RM 98 to 150)and,to a lesser extent,Deadman Creek. Pre:vious studies have examined general abundance patterns,habitat uti.lization,fall densities,colony composition,and overwinter survival (Gipson et al.1982,1984;Woolington et al.1984,1985).This report draws liberally from these sources. The objective of the fall 1985 beaver cache survey was to estimate the number of beaver colonies attempting to overwinter in the Susitna River fl()odplain between Talkeetna and Portage Creek.Data gathered from the survey are compared with similarly collected data from 1982 to 1984,and may be used in connection with a 1986 pre-and post-breakup survey to estimate oVlarwinter survival. Study Area The study area (Figure 1)encompasses the floodplain of the Susitna River between its confluence with the Talkeetna River and its confluence with Portage Creek.Although some areas within the floodplain are likely beyond the hydrologic influence of the Susitna Hydroelectric Project,they were included in the survey because beavers occupying these areas likely forage in portions of the floodplain that will be influenced by the project. 429353 860310 1 RIVER o 5 10 miles ~o 5 10 15 kilometers "".••Cl....,_• ..... ..- I - ..... - - - .- FIGURE 1.Regional map showing features of the middle Susitna River.Alaska. Beaver study area consists of the floodplain of the Susitna River between.Talkeetna and Portage Creek • 2 r - - I"'"" I: ,.... Method s As in previous aerial surveys of this reach of the Susitna River (Gipson et a1.1982,1984;Woolington et al.1984),a Bell 206 helicopter was used to look for beaver food caches from the air.Each food cache supports an overwintering lodge and/or bank den colony with food beneath the winter ice. As noted by various authors,cache surveys are probab ly the most accurate method of establishing numbers of beaver inhabiting an area (Hay 1958, Murray 1961,Koontz 1968,Machida 1982)since each overwintering colony constructs one or more caches in the fall,and the average number of beaver per colony can be determined for a given geographical area.When more than one active cache were found in close proximity,they were deemed to be the winter food reserves of one active colony. ThE~current survey was conducted on October 4,1985.Helicopter personnel included a pilot and two experienced observers.One observer kept the flight log and recorded comments at caches;the other served as navigator and recorded cache locations on aerial photos (approximate scale:1 inch = 3,000 feet). Each coLony location was classified as to the habitat 1n which it occurred. Th4:classification scheme used follows that set forth by the Alaska Department of Fish and Game (ADF&G)Aquatic Study Team (ADF&G 1983): ,.... I o Mainstem habitats are those channels of the river that convey more than approximately 10 percent of the total flow at a given site. During the open water season these channels are characterized by turbidity from glacial meltwater. - o Side channel habitats are those channels of the river that convey less than approximately 10 percent of the total flow.During the open wa ter season these channels are characterized by turb idi ty from glacial meltwater. 429353 860310 3 ..... - - o o o o Side slough habitats contain clear water.Local surface water runoff and upwelling groundwater are the primary sources that supply these habitats.Side sloughs have nonvegetated upper thalwegs that are overtopped during periods of moderate to high mainstem discharge.Once overtopped.side sloughs are considered side channels. Upland sloughs are clearwater habitats that depend upon upwelling groundwater and/or local runoff for their water sources.Upland sloughs have vegetated upper thalwegs that are seldom overtopped by mainstem discharge. Tributary mouths are clearwater habitats at the confluences of tributaries.where clear water mixes with turbid water.If a backwater occurs as a result of mainstem stage.tributary mouth habitat extends into the tributary channel to the upstream extent of the backwater. Tributary habitats are clearwater reaches of tributary streams upstream of the tributary mouth habitats. - - On October 18.1985.a reconnaissance flight was made from the mouth of the Susitna River to Devil Canyon.including the beaver survey reach.Several caches marked as questionab Ie or abandoned during the October 4 survey were examined,particularly along the mainstem,and observers on the flight were requested to look for caches as a double-check on the October 4 survey. Results A total of 42 active colonies were observed on October 4,1985 (Table 1). The weather was clear and sunny,with excellent visibility.Most deciduous trees were leafless.and a thin layer of ice was present on undisturbed ponds and portions of sloughs.Two additional a~tive colonies were found 429353 860310 4 - - - during the October 18 flight t bringing the 1985 total to 44 active colonies. One of these additional colonies was in a mainstem location which had signs of activity on October 4 t but no cache.The other was at a side slough colony site categorized as abandoned during the October 4 flight. The Susitna River flow at Gold Creek was declining after a moderately high flolWi'the last half of September (Figure 2).Although the flow the day of the survey was higher than that during the past two surveys (Table 2),it was within normal flows (Figure 2). Between one and 14 beaver have been reported to occupy each active colony dent with an average of five beaver used for population estimates in Alaska (Koontz 1968 t Boyce 1974 t Woolington et a1.1984).Therefore,the 44 colonies observed during fall 1984 represent an estimated 220 beaver. As shown 10 Table 1,the observed habitat use patterns for caches have varied each of the four years of the surveys.In 1985,the majority of cac:hes were found in upland slough habi tat,followed by side channe 1,side slough,and mainstem habitats.No caches were found in tributary or tri.butary mouth habitats. Discussion Two major types of variability have been seen during the four years of fall beilver studies:numbers of food caches seen during the survey,and the habitats these caches are in. ..... 429353 860310 5 """' ...... 429353 860310 Table 1.Aerial counts of active beaver colonines within the floodplain of the Susitna River between Devil Canyon and Talkeetna,Alaska.Habitat types are according to ADF&G classifications (ADF&G 1983). 6 j J 1 )-1 -)--1 J J -]]J J 682 r 690 I ......... f/) ~ W> 0m< 688 ...W W U...... Z 0 I-<>W.... UJ 686 W C!J 0( l- f/) II: W 684 ~II: -......------~~~-.:...~'""---=---.._--.._--.. NOV.,OCT.SEPT. 1981 /\ AUG. 5 1 982SEPT,1 ,/X,"63 ;.. r~: \ I ............/ ' I A."I,'\LL~/'\l~84 \1£:1965.X'\/\,,19,.~,\'\,\\~/\"'-,~~-",\..OCT.<."'5\'"I "82 "\--<,"\ .r.OCT.4,1984...........-..£.....--....--./,~-4,...(r ••----\'---_.....v .............---........'- 40 10 20 30 SOl ~ UJwa: 0 Q.... 0 C!J I-<..... II-() u.. 0 f/) 0z< f/) ~ 0 ::t I- .......-f/) :t 0.... IL >-.... :II:: Ww :t z<w ~ o J Iii i •'ii •I'iii ,Iii lit 44 45 46 47 48 49 50 51 52 WATER WEEKS 2 3 4 5 6 7 8 9 FIGURE 2.MEAN WEEKLY FLOWS AND STAGES OF SUSITNA RIVER,ALASKA,AT THE GOLD CREEK GAGING STATION DURING THE FALLS OF 1981 TO 1985.·X·s REPRESENT FLOW ON CACHE SURVEY DATES DATE Table 2.Characteristics of beaver cache aerial survey periods along the Susitna River, Alaska,from 1982 to 1985. - Year 1982 1983 1984 1985 429353 860310 Date 15 September 18-19 September 4 October 4 October Susitna River flow at Gold Creek (cis) 28,200 7,560-7,830 7,380 10,400 8 Comments high,turbid flows due to rains sloughs icing over weather clear; no ice clear;light ice on ponds and along shores - - The year-to-year differences in numbers of caches seen (Table 1)could be fro1lll several sources: o Learning may help observers to be more observations because of "known"locations caches,or help locate caches where beavers rather than traditional lodges. accurate,bias their of previous years' are using bank dens -o The beaver population may be increasing rapidly. ..- I - - - o The hydrologic regime at the time of or pr10r to the survey may have a large effect upon survey results. o The timing of the survey relative to initiation and completion of cache-building may affect cache sightability. Hydrologic regime,survey timing,and observer experience are likely the factors having the greatest effects upon the middle Susitna River surveys. Observers become more proficient at noticing caches from the air with experience,as well as learning "typical"and traditional locations of colony lodges,dens,and caches.This is particularly important where beavers are using bank dens since such dens often have litt Ie or no stick mass at the entrance during the first few years of use.With time,some bank dens develop the look of "regular"lodges as a stick mass accumulates • Hydrologic reg1mes likely affect both the beaver and the observers.High water 1S often turbid,obscuring caches and lodges as it rises,and can break caches apart as was seen in 1982 (Gipson et ale 1982).Beaver likely build their caches at a time when water levels are falling and stabilizing at winter flow rates (Figure 2),and surveying too early in the fall may result 1n cache construction not being far enough along for accurate counting. 429353 860310 9 - The large differences in habitat use in different years (Table 1)may be at least partially attributable to August and September flow regimes.High flows during September seem to decrease the proportion of caches built along the main stem 0982,1985).In 1984,flows declined markedly in late August (about when cache construction begins in earnest)and stayed fairly stable throughout September.That year,beaver used mainstem,side slough,and upland slough habitats in about equal proportions.Many side channels were likely dewatered at this time.In 1985,flows were similar to those of 1984 through the first of September,then increased markedly for most of September.Beaver showed a major shift in habitat use this year,making increased use of side channel and upland slough habitats.Perhaps 1985 flow ~n 111lainstem habitats were too fast for cache construction,and beaver moved to available upland slough habitats and the lower velocity,watered side chalo.nels.The lack of caches in side sloughs during 1985 is puzzling. Perhaps fluctuating water levels in these sloughs discouraged building by beaver,since such changes cause rather large wet ted surface area changes in this habitat. It a likely that the 1982 and 1983 surveys under-estimated the actual number of overwintering colonies due to high water and timing,and 1ce cover,respectively (Woolington et a1.1984).The 1984 survey is believed to be accurate and complete,and the total number of active colonies seen, and hence overwintering beaver,is nearly the same as that for 1985.For this reason,we do not believe that the middle Susitna River beaver population is undergoing a major increase,but rather that we now have a realsonab ly accurate estimate of the beaver population. The~possibility that beavers build caches at different times in different habitats (Woolington et ale 1984)was explored during the 1985 survey. Three mainstem lodges which had no caches on October 4,1985,nonetheless had fresh signs of lodge maintenance and had caches during the winter of 1984.These lodges were re-examined during the October 18,1985,flight, and one was found to have a newly constructed food cache.Since water levels stabilize and ice forms earlier in low velocity habitats (upland slough,side slough)than in higher velocity habitats (side channel, 429353 860310 10 ..... - ..... - .... -i I ..... mainstem),it seems plausible that beaver might time cache construction differently 1n these different habitats.At present,however,this scenario has little substantive data to refute or support it. Questions have been rai sed as to the like lihood of long-term trends 1n bea\rer populations and habitat availability in the middle Susitna River basin.Although no quantification of habitat is possible at present, comparisons of aerial photos of the middle Susi tna River since 1949 show no cle~lr patterns of change in river morphology or distribution of vegetated areas (Labelle et a1.1985).Shifts in distribution of plant species may havl:had a larger,more definite role 1n beaver population trends than has geomorphology.Suitable food species must be present to support an active colony.Areas along the middle Susitna River can be seen where old, abandoned beaver dam systems are surrounded by herbaceous vegetation and spruce,both of which are unsuitable food for overwintering beavers (Gipson et al.1982).These areas generally had numerous stumps from balsam popular,alder,and willow removed by beaver.In this manner,increasing beaver popu la tions would acce lerate floodplain succession to spruce forest, reducing available beaver habitat and beaver populations. Any long-term population trend which might be found would be a combination of historical trapping pressures,beaver production levels in tributaries entering the Susitna River,and in availability of suitable food plants on a continuing basis. Summary A total of 44 active beaver colonies were observed within the floodplain of thE!Susitna River between Talkeetna and Portage Creek during survey flights on October 4 and 18,1985.These colonies represent an overwintering population of about 220 beaver.Upland slough habitats were most frequently thE:site of caches observed (52%),followed by side channel (18%),side slough (14%),and mainstem (14%)habitats • 429353 860310 11 -The 1984 and 1985 cache surveys produced nearly equal numbers of active beaver colonies in the middle Susitna River floodplain,although shifts in habitat use were observed.These two surveys are believed to be much more accurate than the 1982 and 1983 surveys.Experienced observers and low, --I ..... - ..... I - stable water levels are believed most responsible for accurate beaver cache surveys. 429353 860310 12 ARLIS Alaska Resources Library &Information ServIces Anch::Jrag':;,f-J..iaska REFERENCES REFERENCES CITED ADF~,G.1983.Susitna Hydro Aquatic Studies.Phase II Basic Data Report. Volume 4:Aquatic Habitat and Instream Flow Studies 1982.Alaska Department of Fish and Game.Prepared for Alaska Power Authority.Doc. No.585. Boyce,M.S.1974.Beaver population ecology in interior Alaska.M.S. Thesis,University of Alaska,Fairbanks.161 pp. Gipson,P.S., Project. Research Doc.No. S.w.Buskirk,and T .W.Hobgood.1982.Susitna Hydroe lectric Furbearer Studies.Phase I Report.Alaska Cooperative Wildlife Unit,Fairbanks.Prepared for Alaska Power Authority. 302. - ,.... - Gipson,P.S.,S.W.Buskirk,T.W.Hobgood,and J.D.Woolington.1984.Susitna Hydroelectric Project.Furbeaver Studies.Phase I Report Update.Alaska Cooperative wildlife Research Unit,Fairbanks.Prepared for Alaska Power Authority.Doc.No.2329. Hay,K.G.1958.Beaver census methods in the Rock Mountain region.Journal of wildlife Management 22(4):395-402. Koontz,K.C.1968.Small game and furbearers of the Rampart Dam impoundment area.M.S.Thesis,University of Alaska,Fairbanks.165 pp. Labelle,J.C.,M.S.Arend,L.D.Leslie,and W.J.Wilson.1985.Susitna Hydroelectric Project.Geomorphic Change in the Middle Susitna River Since 1949.Arctic Environmental Information and Data Center.Prepared for Alaska Power Authority.Doc.No.2827. Machida,S.1982.Report on beaver.Pages 115-121 in Annual Report of Survey Inventory,Progress Report.Alaska Department of Fish and Game. Projects W-19-1,W-19-2,Job Nos.7.0,10.0,14.0,and 15.0. Murray,D.E.1961.Some factors affecting the production and harvest of beaver in the upper Tanana River,Alaska.M.S.Thesis,University of Alaska,Fairbanks.103 pp. Woolington,J.D.,P.S.Gipson,and D.Volsen.1984.Susitna Hydroelectric Project.Furbearer Studies.Fall 1984:Beaver.LGL Alaska Research Associates,Inc.,and Alaska Cooperative wildlife Research Unit, Fairbanks.Prepared for Alaska Power Authority.Doc.No.2592. Woolington,J.D.,R.H.Pollard,and P.S.Gipson.1985.Susitna Hydroelectric Project.Furbearer Studies.Spring 1985:Beaver.LGL Alaska Research Associates,Inc.,and Arkansas Game and Fish Commission.Prepared for Alaska Power Authority.Doc.No.2925. -429353 860310 13 APPENDICES r r .- ..... ..... 429353 860310 Appendix A Notes and habitat utilization observations made during 1985 beaver cache survey along the middle Susitna River,Alaska • 14 Colony No. 1985 BEAVER CACHE SURVEY Habitat 1..1 Comments - -. - -I 85-1 85-2 85-3 85-4 85-5 85-6 85-7 85-8 85-9 85-10 85-11 85-12 85-13 85-14 85-15 85-16 85-17 85-18 85-19 85-20 85-21 85-22 85-23 85-24 85-25 85-26 85-27 85-28 85-29 85-30 us US US ss SC MS MS US US US US US US US MS US US US sc sc SS MS pond US US MS SS US S8 8C beaver seen double cache;beaver seen small cache beaver seen new lodge;large cache;beaver seen large cache;large lodge new lodge;lodge at base of birch cache mostly alder;beaver seen? 3 lodges;1 large cache cache mostly alder bank lodge in eddy of balsam poplar 2 beaver seen large lodge bank den cache packed under downed logs in river 2 lodges;ca.che (&lodges?)under fallen birch cache under fallen balsam poplar beaver seen large cache 15 ..... 1985 Beaver Cache Survey Page 2 ./"'" ; ..... 85-31 85-32 85-33 85-34 85-35 85-36 85-37 85-38 85-39 85-40 85-41 85-42 85-43 85-44 US SC SC SC SS US US US US US US SC MS S8 no activity recently (ice still on surface) cache anchored in root mass of fallen spruce large cache very large cache;pond iced over la.rge cache;large lodge large cache sighted 18 Oct.;same location as 84-41 sighted 18 Oct.;visible portion of cache alder NOTES:(4 October survey) -84-8 84-9 84-17 84-41 looks abandoned lodge/bank den just downstream from this location;no cache ~of trails,cuttings,etc.,but no cache a few cuttings of small sticks;no cache'? 1/MS =Mainstem SC =Side Channel SS =Side Slo~gh US =Upland Slough pond u one small pond near Curry;within floodplain of Susitna River 16 - 429353 860310 Appendix B Locations of active beaver colonies seen along the middle Susitna River,Alaska,during fall 1985 surveys. 17 ~S-J1 TALKEETNA STATION ----8'5-'1 ~~-Slough 2 •"85'-/0 A MITCH LINE ~c Whiskers Creek o RillerMiJe ",.., - ""'" - - SLOUGH AND TRI BUTARY INDEX • =Fall 1985 Beaver Colony 18 -I -I .- I ..... ..... r ..... o a F.'ivtirMde Slough 6A --- .-'t---~5 -It 3 e-'#"'/7 --Lane Creek Gash Creek 'is-I''!-. Oxbow 1 'i/'S-13--. Slough 6 ~S-J:l--- Slough 5 _~..;..;A.....,;MATCHLINE SLOUGH AND TRrSUTARY INDEX • =Fall 1985 Beaver Colony 19 ~gaS"-;l3 0- C RiverMile T)-:Z:l ..... ..... I ...... ..... ...... - ~--Slough 88 Slough BC Slough 80 ~-al --U-6IJlI ----Lower Me Kenzie Creek '15-/'if RM 115 IRKm 1.;.;.8...;.;.S)...r::.L...I....I...;;;;B~MATCHLlNE SLOUGH AND TRIBUTARY INDEX •~Fall 1985 Beaver Colony 20 o MATCHLINE W---"lS-A7 "'1---Slough 9 -__95-31 -Slough A -Skull Creek -Slough A' 'i'S -30 --!-'-J1lJ RM 12:'(11K'":!l)/' Fifth of July creek'/ o Ril',~r Mile Q ..... r ..... - SLOUGH AND TRIBU-mRY INDEX • =Fall 1985 Beaver Colony 21 ""'"I o C RilJl!rMile E MATCHllNE f'".~'11----.\J Slough 16 ?5"~3'l--. Slough 15- GOLD CREEK STATION 12 Slough 10 '6'.5"-33 ---t'l SLOUGH AND TRIBUTARY INDEX • =Fall 1985 Beaver Colony 22 r - - - - o Slough 21 E MA'·CHLINE "'.,--Slough 21 A NOTE:No caches sighted in this reach during fall 1985 survey. r SLOUGH AND TRIBUTARY INDEX e=Fall 1985 Beaver Colony 23