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Baited Lines: An Active Nondestructive Collection Method for Burrowing Crayfish
Zachary J. Loughman, David A. Foltz II, and Stuart A. Welsh

Southeastern Naturalist, Volume 12, Issue 4 (2013): 809–815

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809 Z.J. Loughman, D.A. Foltz II, and S.A. Welsh 22001133 SOUSoTuHthEeAaSsTteErnR NN aNtuArTaUliRstALIST 1V2o(4l.) :1820,9 N–o8.1 45 Baited Lines: An Active Nondestructive Collection Method for Burrowing Crayfish Zachary J. Loughman1,*, David A. Foltz II2, and Stuart A. Welsh3 Abstract - A new method (baited lines) is described for the collection of burrowing crayfishes, where fishing hooks baited with earthworms and tied to monofilament leaders are used to lure crayfishes from their burrow entrances. We estimated capture rates using baited lines at four locations across West Virginia for a total of four crayfish taxa; the taxa studied were orange, blue, and blue/orange morphs of Cambarus dubius (Upland Burrowing Catfish), and C. thomai (Little Brown Mudbug). Baited-line capture rates were lowest for C. thomai (81%; n = 21 attempts) and highest for the orange morph of C. dubius (99%; n = 13 attempts). The pooled capture rate across all taxa was 91.5% (n = 50 attempts). Baited lines represent an environmentally nondestructive method to capture burrowing crayfishes without harm to individuals, and without disturbing burrows or the surrounding area. This novel method allows for repeat captures and long-term studies, providing a useful sampling method for ecological studies of burrowing crayfishes. Introduction Collection methods for crayfishes can be evaluated and compared by estimating sampling efficiency. Collection gear efficiency is often correlated to the animal’s habitat needs and natural history (Ridge et al. 2008). Methods to collect tertiary burrowing crayfish, which do not readily burrow and live primarily in waterways that do not experience drawdown, include seining, dip netting, electrofishing, trapping, and hand collection (Hobbs 1981, Jezerinac et al. 1995). Several survey efforts have focused on tertiary burrowing crayfishes, leading to an understanding of which methodology is most efficient in a given lentic or lotic habitat. Few research studies have focused on primary and secondary burrowing crayfishes relative to those of tertiary burrowing taxa (Larson and Olden 2010, Taylor et al. 2007). Secondary and primary burrowers remain relatively unknown ecologically, primarily due to difficulties associated with collecting these burrowing crayfish (Hobbs 1981, Larson and Olden 2010, Loughman and Simon 2011, Taylor et al. 2007). Secondary burrowing species, which utilize surface water during active hydroperiods and burrow during drawdown conditions, can be collected using tertiary burrower methods when surface water is available. Unlike secondary burrowers, which burrow in response to drawdown conditions, primary burrowers utilize burrows for the majority of their life cycle (Hobbs 1981). Primary and secondary burrowing crayfishes traditionally are collected by excavation of burrows (Ridge et al. 2008), 1West Liberty University, Department of Natural Sciences and Mathematics, West Liberty, WV 26704. 2Marshall University, Department of Biological Sciences, Huntington WV 25755. 3US Geological Survey, WV Cooperative Fish and Wildlife Research Unit, 322 Percival Hall, Morgantown, WV 26506. *Corresponding author - zloughman@westliberty.edu. Z.J. Loughman, D.A. Foltz II, and S.A. Welsh 2013 Southeastern Naturalist Vol. 12, No. 4 810 except during late-winter and early spring when they can be trapped or hand collected from ephemeral pools (Hobbs 1981, Loughman and Simon 2011, Taylor and Anton 1998). Burrow excavation is only moderately successful, physically demanding, time consuming, environmentally destructive, and particularly difficult in certain habitats (Hopper and Huryn 2012, Ridge et al. 2008). Researchers have collected burrowing crayfishes using several methods, including visual night searches (Hobbs 1981, Loughman 2010, Loughman and Simon 2011), burrowing crayfish traps (Norrocky 1984), burrowing crayfish nets (Welch and Eversole 2006), and reversed pitfall traps (Hopper and Huryn 2012). Burrowing crayfish traps, burrowing crayfish nets, and reversed pitfall traps are nondestructive passive methods that trap burrowing crayfish following times of high crayfish activity within or outside the burrow. These collection methods produce little or no significant damage to crayfish burrows and the surrounding area, and allow for mark-recapture and life-history studies, as well as s ampling in imperiled habitats (Hopper and Huryn 2012, Welch and Eversole 2006). In keeping with this approach of collecting burrowing crayfish while minimally impacting burrowing crayfish colonies, a new baited-line method was developed. This study describes baited-line use by determining capture rates for burrowing crayfishes occurring in multiple habitats from across West Virginia. Figure 1.Study sites in West Virginia where baited lines were tested. 811 Z.J. Loughman, D.A. Foltz II, and S.A. Welsh 2013 Southeastern Naturalist Vol. 12, No. 4 Methods Study area Four sites in West Virginia with primary burrowing crayfish populations were sampled with baited lines for this study (Fig. 1). The first site was a bottomland forest associated with a Kanawha River backwater in Poca, Putnam County. Cambarus thomai Jezerinac (Little Brown Mudbug) was the only primary burrowing species present at this site. The second site was a mesophytic forest located in Kanawha State Forest’s campground, Kanawha County. The blue/orange morph of Cambarus dubius Faxon (Upland Burrowing Crayfish; a primary burrower) reached high densities in depositional wetlands and seeps present at the campground. The third site was an old field and adjacent roadside ditch in Chief Cornstalk Wildlife Management Area, Mason County populated by C. dubius (blue morph) and C. thomai. The fourth site was a residential yard and roadside ditch located in Terra Alta, Preston County populated by C. dubius (orange morph). Description of baited-line method Prior to deployment of baited-line rigs, burrow colonies were located during daylight hours. We flagged active burrows and returned to them after dark. Baited-line rigs were assembled using a 2-cm fishing hook (size 6) tied to a 30- cm section of fishing line (Fig. 2). Two 0.5-g split-shot sinkers were placed on the lines 5 cm above the junction point with the hooks. When the rig was completed, we threaded 2.5-cm sections of Lumbricus terrestris L. (Canadian Night Crawler) onto the hooks. The use of a hook is crucial to the success of the rig. During initial trials with bait tied to the end of fishing line, crayfishes detached the bait from the rig by cutting the worms, retreated into their burrows, and rarely returned to the surface. One hour after nightfall, researchers wearing headlamps searched burrow colonies for crayfish resting in burrow portals. Use of a headlamp was crucial during this process because it freed investigator hands to use the rig and grasp crayfishes. Crayfishes were initially spotted in burrows using the primary beam of headlamps. Following initial illumination, the periphery of the beam was used to illuminate animals during the capture process. Crayfishes rarely retreated into burrows when illuminated with the periphery of the beam, but often retreated quickly down the burrow when spotlighted at close range with the primary beam. We deployed a Figure 2. Schematic of a baited-line rig. Baited lines consist of (A) size-six fishing hooks attached to (B) 5–10-cm monofilament leaders tied to (C) 25–60-cm monofilament lines. Baited lines are weighted with (D. 0.5–2.0-gram fishing weights placed at the leader/line attachment point. Z.J. Loughman, D.A. Foltz II, and S.A. Welsh 2013 Southeastern Naturalist Vol. 12, No. 4 812 baited line when the crayfish were within our reach. We lowered the line into the burrow and gently tapped the crayfish’s antennae or chelae with the bait. Crayfishes typically responded to this stimulus by moving towards the bait and grasping at it with their chelae. If this response was initiated, crayfishes were led 5–10 cm from the burrow portal over a 5–20 second period and then grasped or pinned to the entrance of the burrow and extracted. It is important to note that crayfishes were not allowed to grasp the bait; once the bait was grasped, most animals immediately began retreating into their burrows. If crayfishes retreated during any part of this process, we revisited the burrows within 15 minutes and repeate d the process. Time of study and calculation of capture rates The study was conducted from 1 June through 23 June 2010 at the previously mentioned localities. A baited-line attempt was considered successful if the crayfish was enticed using the baited line within one hour of the initial attempt, otherwise it was classified as a failure. Capture rate was calculated by dividing the number of captures by the number of attempts. Results A total of 50 baited-line attempts were made: 21 with C. thomai, 2 with blue phase C. dubius, 13 with orange phase C. dubius, and 14 with blue/orange phase C. dubius. Capture rates were highest for blue and orange phases of C. dubius, at 100% and 99%, respectively (Fig. 3), though it is important to note that only two blue phase Figure 3. Individual taxa and pooled baited line capture rates. n = number of attempts. 813 Z.J. Loughman, D.A. Foltz II, and S.A. Welsh 2013 Southeastern Naturalist Vol. 12, No. 4 C. dubius were observed during the study. Cambarus thomai capture rates were the lowest at 81% (Fig. 3). The pooled capture rate for all crayfishes was 92%. Discussion The current study and a literature review catalog a wide range of capture rates for various burrowing crayfish collection methods. Welch and Eversole (2006) reported a 20% capture rate for burrowing crayfish nets. Excavation had a capture rate of 41% in Ridge et al. (2008). Norrocky trap success rates ranged from a low of 5% (Ridge et al. 2008) to a high of 13% (Norrocky 1984), and the single study testing reversed pitfall traps estimated an average capture rate of 17% (Hopper and Huryn 2012). Of all the methods considered in the literature review, baited lines had the highest average capture rate, with 92% of sampling efforts producing a burrowing crayfish. Baited lines represent a nondestructive way to collect burrowing crayfishes without drastically disturbing the surrounding area. Successful application across a wide range of habitats is an advantage of this method. In our study, baited lines were successful at capturing primary burrowers in bottomland forests, mesophytic forests, depositional wetlands, spring seeps, old fields, roadside ditches, and residential yards. We believe that the baited-line method works best after dark, when crayfishes are observed within burrow portals, and that this method is completely ineffective during daylight hours (Z. Loughman, pers. observ.). Historically, burrow excavation has been the primary method of collecting burrowing crayfishes (Hobbs 1942, 1981; Jezerinac et al. 1995). This method does not work well across a wide range of habitats, particularly at sites where soils are not easily shoveled. Soils in upland forests have compacted regoliths and more roots, rocks, and other impenetrable objects than bottom lands. In open bottomland situations, where alluvial soils are easily shoveled, excavation can be an effective method of capturing burrowing crayfishes. Ridge et al. (2008) investigated the effectiveness of burrowing crayfish nets, burrow excavation, and Norrocky traps in Indiana bottomlands. Excavation was the most effective method, which was likely due to the ease of digging in the alluvial soils of the Indiana bottomlands. Forests in the uplands of the Appalachians are much more compact and complex, making excavation an inefficient strategy in this region. Burrowing crayfish nets work well if conditions are ideal for deployment, but are ineffective during drought situations and other times with low relative humidity (Ridge et al. 2008, Welch and Eversole 2006). On occasion, burrowing crayfish nets entangle individuals to the point of injury (Ridge et al. 2008, Welch and Eversole 2006). While burrowing crayfish nets are passive gear, entangled crayfish can become ensnared on debris in the burrow, resulting in the burrow ultimately having to be excavated (Z. Loughman, pers. observ.). Baited lines have several advantages over other sampling methods. Burrowing crayfishes can be collected quickly en masse when conditions are ideal. Using baited lines at the Chief Cornstalk Wildlife Management Area, we collected 15 C. thomai in the same amount of time (10 min) it takes to excavate a single burrow. Z.J. Loughman, D.A. Foltz II, and S.A. Welsh 2013 Southeastern Naturalist Vol. 12, No. 4 814 Impacts to the surrounding area during baited-line capture are limited to those associated with foot travel of investigators. Because the baited-line capture method is used at night when burrowing crayfishes are active, direct behavioral observations of these taxa are possible in situ. Recent review papers on crayfish conservation have noted a pressing issue in astacology: a lack of basic life- and natural history information on crayfishes, specifically burrowers (Larson and Olden 2010, Taylor et al. 2007). The use of sampling with baited lines will likely lead to further insight into burrowing crayfish natural history. Given that baited lines work well when crayfishes are observed at burrow portals, ancillary behavioral and ecological observations are possible before or during use of this collection technique. Prior to capturing crayfishes with this method researchers can make pertinent behavioral observations including foraging behaviors and diet preferences, burrow construction and maintenance behaviors, interactions between conspecifics in the burrow, and surface utilization. With baited lines, crayfish can be captured unharmed and placed back into their resident burrow, making longer term ecological studies possible, which is another need specific to primary burrowing crayfishes (Larson and Olden 2010, Loughman and Simon 2011). The same animal can be captured on successive nights, and even multiple times in the same night (Z. Loughman and D. Foltz, pers. observ.). Excavation immediately eliminates this possibility given its destructive nature. Although baited lines are effective in many sampling conditions and habitat types, limitations do exist and should be considered prior to adoption of this method. Baited lines are not effective during daylight hours when burrowing crayfishes are less likely to be observed resting at burrow portals. Further, the method is less effective in habitats with tall vegetation, when burrows are difficult to find, and when baited lines are not easily deployed into burrow portals (Z. Loughman, pers. observ.). Situations that are not conducive to burrowing crayfish activity (i.e., periods of low relative humidity, or drought conditions) will also likely result in low capture success. Baited lines provide an additional sampling method for the collection of burrowing crayfishes. Like most methods, baited lines have advantages and disadvantages. For sampling of burrowing crayfishes, the use of baited lines in combination with other sampling techniques will increase sampling success, especially when faced with a range of field conditions and habitat types. Acknowledgments We would like to thank Nicole Garrison, Tricia Kangisser, and Nate Taylor for assistance in the field, and West Liberty University’s Department of Natural Sciences and Mathematics for financial assistance. Comments from three anonymous reviewers greatly increased the quality of the manuscript. The use of trade names or products does not constitute endorsement by the US Government. 815 Z.J. Loughman, D.A. Foltz II, and S.A. Welsh 2013 Southeastern Naturalist Vol. 12, No. 4 Literature Cited Hobbs, H.H., Jr. 1942. Crayfishes of Florida. University of Florida Publications of Biological Science Series 3. 179 pp. Hobbs, H.H., Jr. 1981. The Crayfishes of Georgia. Smithsonian Contributions to Zoology. 318:1–549. Hopper, J.D., and A.D. Huryn. 2012. A new, non-destructive method for sampling burrowing crayfish. Southeastern Naturalist 11:43–48. Jezerinac, R.F., G.W. Stocker, and D.C. Tarter. 1995. The crayfishes (Decapoda:Cambaridae) of West Virginia. Bulletin of the Ohio Biological Survey, New Series 10:1–193. Larson, E.R., and J.D. Olden. 2010. Latent extinction and invasion risk of crayfishes in the southeastern United States. Conservation Biology 24:1099–1110. Loughman, Z.J. 2010. Ecology of Cambarus dubius (Upland Burrowing Crayfish) in northcentral West Virginia. Southeastern Naturalist 9(Special Issue 3):217–230. Loughman, Z.J., and T.P. Simon. 2011. 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Comparison of two burrowing crayfish trapping methods. Southeastern Naturalist 5:127–30.