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Surveying for hellbender , Cryptobranchus alleganiensis (Daudin): Areview and critique

MaxA. Nickersonand Kenneth L. Krysko

Universityof Florida,Florida Museum of Natural History, P .O.Box117800, Gainesville, FL32611-7800,USA e-mail:maxn@ mnh.u .edu, kenneyk@ mnh.u .edu

Abstract. Wereview the wide array of techniques and their variants used in studyinga cryptobranchid salamanderand discuss their advantages and disadvantages. Electroshocking surveys are strongly discouragedbecause of the great potential for damaging reproductive success, immune systems, andtheir questionable effectiveness. Because successful Cryptobranchusalleganiensis nestingsites appearto be quitelimited, the use of Peavy hooks and crowbars to breakupbedrock or dislodgelarge coverrocks should be restricted. Currently, skin-diving surveys coupled with turning objects is the onlymethod shown to obtainall sizes of gilled larvae and multiple age groups of non-gilledand adult C.alleganiensis inbriefperiods.

Key words: ;collecting; Cryptobranchus ;ecology;hellbender; ; survey; technique.

Introduction Thefamily Cryptobranchidaeincludes onlythree extant , the giant sala- manders Andriasdavidianus from China, A.japonicus fromJapan, and hellbender, Cryptobranchusalleganiensis fromcentral andeastern UnitedStates. BothAsi- atic giant salamanders are protectedwithin their respective countries.Additionally , A.japonicus is listed as Vulnerableby the IUCN(Nickerson,2002). Hellbenders havebeen listed as endangered,threatened, species ofspecial concern,or other- wise protectedin most states throughouttheir range(Levell, 1995). Surveys have shownsubstantial declines in most populationswhere density was known,and pop- ulationcollapses in others (Trauthet al., 1992,1993; Wheeler et al., 2003).The Ozarkhellbender, C.a.bishopi ,is acandidatefor the U.S.Fish andWildlife Ser- vice Threatenedand Endangered species listing (USFWS,2002). Because fewor noecological studies of C.alleganiensis havetaken place in most states, wereview

© KoninklijkeBrill NV ,Leiden,2003 APPLIEDHERPETOLOGY 1: 37-44 Alsoavailable online - www.brill.nl 38 MaxA. Nickersonand Kenneth L. Krysko previoussurvey methods and discuss their advantagesand disadvantages to aid fu- ture studies, especially relating to conservation.Although this reviewfocuses on C.alleganiensis ,it is applicable to studies onall cryptobranchidsalamanders.

Review Williams et al. (1981)evaluated Ž veknown and potential sampling techniquesfor C.alleganiensis ,including(1) walking a stream, search andseizure, (2)walking a stream andturning rocks with arake,search andseizure, (3)electroshocking and dipnetting, (4) seine herding,and (5) electroshocking with seining. Each of the Žvetechniques was usedfor one hr each day within the same sample plot,with a 1hinterval betweentechniques (Williams et al., 1981).The sampling periodwas rotated so that eachtechnique was appliedonce in each time period(01:00-10:00 and15:00-24:00 hrs) duringthree Žve-dayperiods at eachof three 200m sample plots (Williams et al., 1981). Turningrocks and other objects while wadinghas beenthe most widelyused capturetechnique for C.alleganiensis (Peterson,1987; T aberet al., 1975).At times, wadingsurveyors have used potato rakes to turnrocks, face masks to reducesurface glare,and dip-nets to scoopup C.alleganiensis .Apeavyhook has beenused to aid surveyorsby alleviating the strain ofbending and kneeling especially whenlifting large rocks(Soule and Lindberg, 1994). Crowbars have also beenused to break bedrockand expose secluded individuals (Peterson,1988). Researchers usingthe wadingand turning technique have obtained large numbers ofindividuals fromOzark streams: 1,132by T aberet al. (1975),744 individuals byPeterson et al. (1983),and 1,208 individuals by Peterson et al. (1988).This techniqueis probablymost effective in relatively clear water, 61.0m in depth,with bottoms that havenumerous rocks and other objects to turn.However, this method is oftenineffective incapturing larvae andindividuals <20cm (Peterson et al., 1983;Nickerson, unpubl. data). Sweeping the area nearand downstream from an overturnedobject with adipnet orplacing a seine downstreammay aid in the captureof these smaller individuals.Advantages are lowequipment costs, quick sampling,and one surveyor can safely workalone. Disadvantages of this method includebeing unable to sample deepwater, the potential formissing hellbenders becauseof glare reected fromthe water’s surface,rapid fatigue, and potential back injuries fromconstant bendingover and lifting. Skin-divinggear (i.e., a wet suit, face mask,snorkle, and Ž ns ortennis shoes) coupledwith turningrocks and logs has beena verysuccessful methodfor capturing C.alleganiensis in Ozarkwaterways of andArkansas (Nickerson and Mays,1973a, b) and streams withinthe Great SmokyMountains National Park (GSMNP)in and (Nickersonet al., 2000,2002). Using this method,up to 96 individualshave been caught and released bya single personin oneday (Nickerson, unpubl. data). Skin-diving surveys have produced many more gilled larvae thanthe wadingand turning method in Ozark studies, eventhough