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Capture Efficiency of Underwater Observation Protocols for Three Imperiled Fishes
Johnathan G. Davis, Jason E. Miller, M. Shane Billings, W. Keith Gibbs, and S. Bradford Cook

Southeastern Naturalist, Volume 10, Issue 1 (2011): 155–166

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2011 SOUTHEASTERN NATURALIST 10(1):155–166 Capture Efficiency of Underwater Observation Protocols for Three Imperiled Fishes Johnathan G. Davis1,2,*, Jason E. Miller1, M. Shane Billings1, W. Keith Gibbs1, and S. Bradford Cook1 Abstract - Underwater observation is a widely used fish-sampling method, but capture efficiencies of this method are often unknown. For accuracy, survey counts require correction by measuring capture efficiencies of sampling protocols. Capture efficiencies for underwater observation were calculated for three small imperiled fishes—Etheostoma sitikuense (Citico Darter), Noturus flavipinnis (Yellowfin Madtom), and Noturus baileyi (Smoky Madtom)—using modified mark-recapture methods. Fishes were tagged with visual implant elastomer tags, released at sites within Abrams Creek in the Great Smoky Mountains National Park, and then recaptured. Efficiencies were calculated by comparing numbers of released individuals to recaptures. In the propagation facility, tag retention was 100 percent, and no post-tagging mortality was observed. Capture efficiency (CE = 0.12) was low for all species and potentially influenced by predation upon marked fish, emigration of fish from sites, or difficulty in sampling some habitats. Thus, population sizes may be larger than observed due to low capture efficiencies. Our results highlight challenges to estimating capture efficiencies for imperiled fishes when using underwater observational methods. Introduction The southeastern United States has the highest diversity of freshwater fishes and the largest number of endemic species in North America (Warren et al. 2000), but also the highest number of imperiled fishes (Warren and Burr 1994). Of the 290 species in Tennessee, approximately 83 taxa of native species are designated with a protective status (Etnier and Starnes 1993). In particular, endemic species of Percidae (i.e., darters) and Ictaluridae (i.e., madtoms) are in greatest jeopardy of imperilment (Etnier and Starnes 1991). Etheostoma sitikuense Blanton (Citico Darter), Noturus baileyi Taylor (Smoky Madtom), and Noturus flavipinnis Taylor (Yellowfin Madtom) are native to southeastern Tennessee and reflect current efforts to restore imperiled native fishes. These fishes were extirpated from Abrams Creek in the 1950s, but were successfully reintroduced through the combined efforts of the National Park Service and Conservation Fisheries, Inc. (Shute et al. 2005). The Citico Darter is a recently described, endangered species (Blanton and Jenkins 2008), formerly known as Etheostoma percnurum Jenkins (Duskytail Darter; Jenkins and Burkhead 1994, Layman 1991). A member of the subgenus Catonotus, the Citico Darter is a benthic species found in moderate gradient streams at shallow depths under cobble and small-boulder substrates in gently flowing pools (Etnier and Starnes 1993, Jenkins and Burkhead 1994). The Smoky Madtom is a small, 1Department of Biology, Tennessee Technological University, Cookeville, Tennessee 38505. 2Current address - Division of Math and Sciences, Nashville State Community College, Cookeville, Tennessee 38506. *Corresponding author- 156 Southeastern Naturalist Vol. 10, No. 1 endangered catfish species found in riffle and run habitats under cobble and smallboulder substrates (Dinkins 1984, Dinkins and Shute 1996). These two fishes are found only in Abrams Creek, Citico Creek, and Tellico River, TN. Once considered extinct (Taylor et al. 1971), the threatened Yellowfin Madtom is found in the upper Tennessee River drainage in portions of Tennessee, Georgia, and Virginia (Etnier and Starnes 1993). Preferring cover such as slabrocks, ledges, and leaf litter, Yellowfin Madtoms inhabit calm pools of moderate-gradient streams (Dinkins and Shute 1996, Jenkins and Burkhead 1994). Distributions of all three species within Abrams Creek are limited by the amounts of cobble and small-boulder substrate (Gibbs 2008, Throneberry 2008). Several methods are available to sample these fishes based on a wide range of conditions (Murphy and Willis 1996). The most popular techniques include electrofishing, seining, and trap netting. However, there are limitations when using these gears that preclude them from sampling small, endangered fishes such as darters and madtoms, most notably sampling mortality. Furthermore, traditional sampling gears are often inefficient at sampling benthic fishes that seek cover under cobble and boulder substrates, woody debris, and rock ledges in streams (Price and Peterson 2010). Underwater observation is the most nonintrusive and non-lethal technique available, but enumerating population size using this method is difficult because capture efficiencies vary based upon species and water body. Capture efficiency is defined as “the percentage of the true number of individuals present at a sampling site that are captured with a specified amount of effort using a type of gear or capture method” (Peterson and Paukert 2009). Biotic characteristics such as body size, behavior, coloration, and morphology and abiotic characteristics such as turbidity, habitat complexity, and stream width and depth can influence fish capture efficiencies for snorkeling (Peterson and Paukert 2009). Long-term monitoring protocols are established to provide repeatable procedures that result in statistically valid and comparable information which can track changes in populations. Routinely, protocols use count data to describe the population. However, if an accurate population estimate is desired, count data must be calibrated by calculating the capture efficiency of the method or protocol employed for the particular species of interest. Estimating capture efficiencies for rare and endangered fishes is inherently difficult. Conducting pilot studies for these species to estimate capture efficiencies can be costly, time-consuming, and cause incidental mortality. Estimating capture efficiency of a particular method involves comparing the number of fish present to an unbiased estimate of the number of fish, which can be estimated in various ways, including stocking a known number of fish into a site (Rodgers et al. 1992), using dual gears (Thurow et al. 2006), and conducting a mark-recapture study to obtain an estimator (Peterson et al. 2004). Although capture efficiencies can vary based upon sampling gear, fish species, and habitat, in general, capture efficiencies for benthic species such as darters, are low (Angermeier et al. 1991, Price and Peterson 2010). However, some darters, such as Etheostoma okaloosa Fowler (Okaloosa Darter), have reported capture effeciencies greater than 0.50 (Jordan and Jelks 2007). When using various electrofishing gears, Burns (2007) reported capture efficiencies of 0.46–0.58 for Etheostoma 2011 J.G. Davis, J.E. Miller, M.S. Billings, W.K. Gibbs, and S.B. Cook 157 flabellare Rafinesque (Fantail Darter). Little information is available on the capture efficiencies of cryptic, benthic darters and madtoms when using underwater observational techniques. The goal of this study was to estimate capture efficiency of the Citico Darter, the Smoky Madtom, and the Yellowfin Madtom using a strategy that reduced cost and time, minimized mortality, and provided an accurate assessment of efficiency. A mark-recapture study was conducted to evaluate the capture efficiency of these three imperiled fishes by using an experimental population in Abrams Creek, TN. Specifically, the objectives were to (1) determine and compare capture efficiencies of each species, (2) analyze visual implant elastomer tagging methods for estimating efficiencies, and (3) determine if predation occurs on marked fish. Capture efficiency estimates from this study can be applied to counts from monitoring these species, and possibly to similar darters and madtoms, to more accurately estimate population sizes. These results will aid conservation biologists in monitoring populations and making informed decisions on the conservation status of these species. Field-Site Description Located within the Tennessee River watershed, Abrams Creek is located in Blount County, TN within the boundaries of the Great Smoky Mountains National Park (GSMNP) in southeastern Tennessee. The watershed is approximately 225 km2, with 348 km of streams (Parker and Pipes 1990). Abrams Creek is a moderately sized, fifth order, coolwater stream with an average temperature not exceeding 23 °C (Schaffer 2004). Abrams Falls, a 6.0-m waterfall, bisects the stream into upper and lower sections. The lower section, containing the sampling sites, extends from Abrams Falls to the embayment of Chilhowee Reservior and has an average width of 18 m and an average gradient of 3.5 percent (Shaffer 2004). This section encompasses all previous reintroduction sites for Citico Darters, Smoky Madtoms, and Yellowfin Madtoms (Rakes and Shute 2007). The dominant substrate in this section consists of cobble, boulder, and bedrock substrates; the dominant habitat type is run habitat (Gibbs 2008, Throneberry 2008). Conductivity and pH are higher in this stream than other streams due to the underlying limestone geologic formation (Gibbs 2008). Methods Tagging and release procedure Citico Darters, Smoky Madtoms, and Yellowfin Madtoms were obtained from Conservation Fisheries, Inc. (Cfi) for tagging and subsequent stocking into Abrams Creek. Fishes were raised in 76-L grow-out tanks operating on a filtered, independent recirculating system (Rakes and Shute 2007). For this study, 200 Citico Darters, 100 Smoky Madtoms, and 100 Yellowfin Madtoms were tagged on 22 September 2009 using visible implant elastomer (VIE) tags. VIE tagging is a non-lethal method in which fluorescent dye is injected subcutaneously into fish and is useful for collecting data on many fish species. These tags have been used previously for monitoring these species and other similar, reintroduced species (Coombs et al. 2004, Shute et al. 2005). 158 Southeastern Naturalist Vol. 10, No. 1 Fish were removed from grow-out tanks and anesthetized using a solution of 100 mg MS-222 per liter of water at 23.2 °C. Individuals were placed in the MS-222 solution for a period of 2–3 minutes before showing effects of anesthesia. Prior to injection, VIE tagging material was prepared by combining colored elastomer at a 10:1 ratio with a curing agent and mixed thoroughly for one minute. VIE material was then transferred to a 0.3-cc syringe for injection into anesthetized fish (Northwest Marine Technologies 2005). Tags were implanted immediately anterior to the dorsal fin in Citico Darters and posterior to the dorsal fin in madtoms. Approximately 100 of 200 Citico Darters were tagged with pink fluorescent-colored elastomer while the other 100 individuals were tagged with green fluorescent-colored elastomer. For madtoms, two batches of 50 Smoky Madtoms were marked with yellow- and orange-colored elastomer, respectively, while two batches of 50 Yellowfin Madtoms were marked with pink- and green-colored elastomer, respectively. Thus, two separate batches of individuals for each species were distinctively marked for stocking at two separate sites (Table 1). After tagging, fish were placed in observation trays and allowed to recover for approximately five minutes before returning them to grow-out tanks. Two sites were chosen based upon the amount of suitable habitat available as derived from previous habitat studies that evaluated success of previous reintroduction efforts (Gibbs 2008, Throneberry 2008). Multiple sites were necessary to account for the variability of sampling conditions encountered under normal circumstances and to increase the capabilities of capture-efficiency models. Sites were located within suggested reaches of suitable macrohabitat for all three species in Abrams Creek (Gibbs 2008, Throneberry 2008; Fig. 1). Sites 1 and 2 were each approximately 50 m in length and 20 m in width. These sites consisted of shallow, slow-flowing water located in transition areas between fast riffle and run habitats with heterogeneous mixtures of mostly cobble and bedrock substrates. Citico Darters and both madtom species have demonstrated a low dispersal rate and an unwillingness to inhabit other habitat types such as riffles or deep, silty pools (Rakes and Shute 2007). Therefore, it was assumed that stocked fish would not traverse these areas to emigrate from the site, but rather that these areas would be barriers to emigration from the site. Fishes were transported from CFI’s rearing facility in Knoxville, TN to the stocking location on 6 October 2009. Prior to transport, individuals were checked for the presence of a tag to ensure tag retention. Fishes were removed from aquaria and placed into 1.0-gallon plastic bags filled half with water and half with 100 percent oxygen gas. Oxygen was pumped into the bag until the bag was completely full and then closed and sealed. Fishes implanted with different colored tags were put into separate transportation bags, with a maximum of 50 individuals per bag. Fishes were transported from the rearing facility at 0900 hrs to Abrams Table 1. Visible implant elastomer tag colors for each species released at two sites in Abrams Creek, TN. The number of individuals released at each site is indicated in parenthesis. Site Etheostoma situkuense Noturus baileyi Noturus flavipinnis 1 Pink (100) Yellow (50) Pink (50) 2 Green (100) Orange (50) Green (50) 2011 J.G. Davis, J.E. Miller, M.S. Billings, W.K. Gibbs, and S.B. Cook 159 Creek Campground. Plastic transportation bags were then loaded into backpacks and transported approximately 2 kms to each stocking site. Upon arrival at each stocking site, bags were removed from backpacks and placed into the stream to acclimate to water temperatures. During each transfer from one holding compartment to the next, fish were checked for mortality. Water was slowly exchanged in the bag by periodically splashing water into each bag. When fish were adequately acclimated (≈45 min), the bag was carried to an exact location within the release site containing an abundance of suitable habitat. Fish were released approximately 1–2 m upstream of this location to account for drift during release. Release occurred at approximately 1430 hrs. During release, fish were observed underwater for ≈30–45 min to determine if any immediate predation was occurring and to note the behavioral response of released fish. Stocking was based on methods developed by Cfistaff during their successful reintroductions of these three species into Abrams Creek over the past 20 years (George et al. 2009, Rakes and Shute 2007). Sampling and recapture of individuals. Prior to sampling, an attempt was made to capture potential predators through hook-and-line sampling at each site. Stomachs were removed from sampled predators and analyzed for VIE tagging material. Underwater observation was used to count marked individuals. Marked fish were considered recaptured when a snorkeler observed an individual underwater. Marked fish were not removed from the population when counted. Snorkelers entered the water downstream of Figure 1. Release-site locations (black squares) and subsequent recapture sites for three imperiled species within the Abrams Creek watershed in Tennessee. Sites were approximately 50 m long and 20 m wide. Thick, black line indicates the waters of Abrams Creek. 160 Southeastern Naturalist Vol. 10, No. 1 release sites, starting just upstream of the most downstream barrier (i.e., riffle) and swam transects upstream parallel to the bank until encountering high flows of the upstream barrier. Starting from the left descending bank, snorkelers were approximately 1.5–2-m apart from one another and proceeded upstream at the same pace, with the overall goal of sampling 100 percent of the available area within the site. Thus, all released, marked fish had the opportunity to be recaptured. Upon encountering a marked fish, snorkelers observed the fish carefully for the presence of a mark. Upon observing a marked fish, observers recorded the encounter by communicating with a team member on the bank who recorded the observation. Fish were assumed to stay within the boundaries of the site. It was also assumed that mortality did not occur between release and sampling. The total number of recaptures was recorded for each site. Two separate surveys were completed at 20 and 44 hours after the initial stocking for each site, resulting in four complete surveys. Estimating capture efficiency Capture efficiencies were calculated by dividing the number of recaptured individuals for each species by the number of released individuals of each species at a site. Descriptive statistics were calculated for each species from all surveys of both sites. Significant differences (α = 0.05) in capture efficiencies between each species were tested using analysis of variance in SAS 9.1 (SAS Institute 2009). Tukey’s post hoc test was used to determine if differences existed in mean capture efficiencies between species. Additionally, because habitat complexity and structure can influence capture efficiency, a site comparison was conducted using mean capture efficiencies from all species at each site. Results Released fish were approximately five months old when tagged. Mortality during tagging of Citico Darters was 0.05 percent, as only one individual did not survive the tagging process. No mortality was observed during tagging of either madtom species. No delayed mortality was observed over the two-week period between tagging and release. Tag retention during this two-week period was 100 percent for all species. Mortality of fish during transportation from the rearing facility to the release site was zero percent. No mortality was observed during the period of underwater observation following stocking. Observations during fish release confirmed the ease of identifying VIE tags on released fish. Observation was halted after approximately 45 minutes in fear of attracting predators and affecting behavior of released fish. Based on observation, Citico Darters did not immediately reflect the behavior of naturalized fish. While some Citico Darters immediately sought cover under available cobble and small boulder substrate, most individuals remained on top of the substrate in the immediate vicinity of the release area (≈1.5–2 m2). This behavior was exhibited until observation concluded. Yellowfin Madtoms displayed similar behavior, whereas Smoky Madtoms immediately sought cover. Survey times at each site varied depending upon field conditions and habitat type. In general, time to completely survey a site varied between 3–4 hrs. Ten transects were required to survey the entire width of the stream. Green and pink 2011 J.G. Davis, J.E. Miller, M.S. Billings, W.K. Gibbs, and S.B. Cook 161 tags were easily observed. The number of recaptures at a site ranged from one to twelve individuals for each species and varied between the two sampling passes at each site (Table 2). Capture efficiencies (CE) for all species ranged from 0.02–0.24. There was no significant difference between the capture efficiencies for each species (P = 0.1237) or between sampling sites (P = 0.1003). Capture efficiencies were lowest for Citico Darters (0.06–0.11) and highest for Smoky Madtoms (0.12–0.20) (Table3). Yellowfin Madtoms were difficult to capture at site 1 (CE = 0.03), but had an increased capture efficiency at site 2 (CE = 0.18). Micropterus dolomeiu Lacepède (Smallmouth Bass; n = 2) were captured at site 1, but none were captured at site 2. Underwater observation did not confirm the presence of any Smallmouth Bass at site 2. Stomach contents of one Smallmouth Bass contained a pink VIE tag and a partially decomposed fish. It was assumed that this fish was a released Citico Darter. Discussion Capture efficiencies were statistically similar for all three species, although similarities may be the result of observing each species in similar habitat. Differences may exist, but were not detected due to low statistical power from small sample sizes. For example, no difference was detected for Yellowfin Madtoms even though they are often considered more difficult to capture (Shute et al. 2005). Furthermore, each species exhibits similar behavior in that they are each small, cryptic fish who seek out cover underneath cobble and small-boulder substrates. Observers did not change throughout the study, and the same individuals surveyed for fish with an equal amount of effort at a site. Thus, differences between capture efficiencies were not due to differences in training, experience, or effort of snorkelers. VIE tags have been successfully used in various fishes including Centrachids (Catalano et al. 2001, Dewey and Zigler 1996), Oncorhynchus mykiss Walbaum Table 2. The number of recaptured fish from each species collected during two mark-recapture sampling events at two sites in Abrams Creek, TN. Site Sample Etheostoma situkuense Noturus baileyi Noturus flavipinnis 1 1 10 2 10 1 2 6 1 6 2 1 6 12 7 2 2 11 6 10 Table 3. Mean capture efficiencies of three imperiled fishes estimated from mark-recapture studies at two release sites in Abrams Creek, TN. Fishes at site one and site two were observed 20 and 44 hours post-release, respectively. No significant differences were detected for capture efficiencies between each species. 95% confidence intervals Species n Mean (± SD) Range Lower Upper Etheostoma situkuense 4 0.08 (±0.03) 0.06–0.11 0.02 0.14 Noturus baileyi 4 0.17 (±0.04) 0.12–0.20 0.10 0.23 Noturus flavipinnis 4 0.11 (±0.10) 0.02–0.24 0.04 0.17 162 Southeastern Naturalist Vol. 10, No. 1 (Rainbow Trout; Close 2000, Close and Jones 2002), Salmo trutta L. (Brown Trout; Olsen and Volestad 2001), and Salmo salar L. (Atlantic Salmon; Fitzgerald et al. 2004). Also, VIE tags do not affect survival and growth (Phillips and Fries 2009). Reported tag-retention rates for VIE tags in darters are high, with up to 100 percent retention. Roberts and Angermeier (2004) reported retention rates of 94 percent after 80 days. Weston and Johnson (2008) reported that retention rates of VIE tags for darters are 100 percent for Etheostoma caeruleum Storer (Rainbow Darter) and 88 percent for Etheostoma moorei Raney and Suttkus (Yellowcheek Darter). Tag retention was 88 percent for Etheostoma fonticola Jordan and Gilbert (Fountain Darter; Phillips and Fries 2009). Tag retention rates for this study are similar to other studies, although tag retention was expected to be high for a period of 14 days. Another criteria that should be considered is choice of tag color, as some colors may be hard to see or hard to distinguish. Curtis (2006) reported that green and yellow VIE tags and red and orange VIE tags are sometimes confused. Therefore, VIE tag color combinations of released fish among sites were pink and green or yellow and orange to prevent any misinterpretation. Tags were easily viewed underwater and identified with certainty by all observers. Observation of Citico Darters and Yellowfin Madtoms immediately after release revealed behavior that was different than resident populations (Gibbs 2008). A majority of Citico Darters did not hide underneath available cobble and boulder substrates, but rather positioned themselves beside or on top of cover rocks. This altered behavior may represent a potential problem in estimating capture efficiency because released fish may have reacted differently to our sampling method than would resident fish. However, most recaptured fishes were found underneath cobble, and only two Citico Darters and one Yellowfin Madtom were not located underneath cover at 20 and 44 hours post-release. Behavioral differences may have resulted from the stress of transport. During propagation and rearing, ample cover is provided for each species, and reared species exhibit similar behaviors to wild populations (Rakes and Shute 2007). Furthermore, all stocked fish are F1 offspring collected from source-population nesting sites. Analysis of stomach contents of Smallmouth Bass (n = 2) captured by hookand- line sampling at 20 hours post-release at site 1 confirmed predation upon Citico Darters. A clearly visible, pink section of a hardened elastomer tag was found in one stomach along with a small portion of bone. This was assumed to be material from a released Citico Darter. Due to small sample size, the rate of predation upon released darters is unknown. Predation should be accounted for if more accurate estimates of capture are to be developed. Darters may exist in smaller densities in the presence of Smallmouth Bass (Magoulick 2004). Another potential predator in these sites was Ambloplites rupestris Rafinesque (Rock Bass). Angermeier (1992) found that Rock Bass preyed upon the Fantail Darter, another Catonotus species similar to Citico Darters, at greater rates in deeper water than in shallow water. Releasing Citico Darters in shallow areas may reduce susceptibility to predation by Centrachid species. Both release sites were chosen based upon the availability of suitable habitat such as cobble and small-boulder substrate in gently flowing pools (Gibbs 2008, Throneberry 2008). However, both sites also contained slabs of broken and unbroken bedrock, which formed deep crevices and ledges that were impossible to 2011 J.G. Davis, J.E. Miller, M.S. Billings, W.K. Gibbs, and S.B. Cook 163 effectively observe. Therefore, many potential hiding places went unsampled, and it is possible that tagged fish may have inhabited these areas, decreasing the overall detection of individuals. Recaptures of darters were not only located in the immediate vicinity of release, but also throughout the majority of the surveyed site. For this study, it was assumed that released fishes would not migrate past downstream barriers, in this case, riffles. The dispersal ability of the Citico Darter is thought to be limited (Gibbs 2008), and dispersal capabilities in general for darters are relatively small (Freeman 1995, McClain and Ross 2005). During a 30-day period, Mundahl and Ingersoll (1983) found that 87 percent of Fantail Darters did not disperse from the original pool of capture. The close proximity of some relocated individuals to these riffles at the downstream margins of sites infers the possibility that some individuals may have left the site. There was no significant difference in capture efficiency from a time of 20 hours to 44 hours, which suggests that the majority of dispersal occurs in the first 20 hours after release. Because of sampling limitations and logistics, areas downstream of release sites were not surveyed to determine if movement occurred across barriers. Recommendations for future stocking of Citico Darters and both madtom species should consider removal of predators from release sites. The behavior of Citico Darters immediately following release makes them highly susceptible to predation. Also, consideration should be given to blocking predator access to individuals in order to allow released individuals to acclimate to their surroundings. Most darters and madtoms recaptured after 20 hrs exhibited behavior consistent with wild populations by seeking cover under cobble and small boulder substrate. For this study, the assumption that emigration did not occur may have been violated. Thus, it may be beneficial to block downstream migration routes with block nets before release as well. The timing of stocking was not conducive to using block nets due to increasing flows and leaf litter in the stream. The capture efficiencies of these three species were negatively influenced by predation of released individuals, inability to effectively sample some areas of release sites, and possible emigration of released individuals from the stocking site. Total mean capture efficiency of these fish was approximately 0.12, but the capture efficiency may actually be much higher. The results of this study can be used to estimate capture efficiencies for similar species in similar sampling conditions. Capture efficiencies for the Citico Darter can serve as a surrogate for the similar Etheostoma lemniscatum Blanton (Tuxedo Darter) or Duskytail Darter because of similarities in appearance, behavior, and habitat preference (Blanton and Jenkins 2008, Eisenhour and Burr 2000). The use of surrogate species to solve problems associated with the conservation of endangered species is common (Caro and O’Doherty 1999). For example, capture efficiencies could be incorporated into monitoring the Tuxedo Darter in the Big South Fork of the Cumberland River, TN to calibrate underwater observation counts (J.G. Davis and S.B. Cook, unpubl. data). Currently, future monitoring is planned for the Citico Darter, Smoky Madtom, and Yellowfin Madtom in Abrams Creek, and estimates of the capture efficiency of underwater observation will improve monitoring of these imperiled species. 164 Southeastern Naturalist Vol. 10, No. 1 Acknowledgments We would like to especially thank Conservation Fisheries Inc., particularly J.R. Shute and Pat Rakes, for their assistance in tagging and transporting fish as well as for providing and propagating all fish for this study. We would also like to acknowledge Steve Moore and Matt Kulp of the Great Smoky Mountain National Park for their guidance and help during planning and implementation of this project. We are grateful to two anonymous reviewers whose comments improved this manuscript. The majority of funding for this research was provided by the National Park Service and the Tennessee Technological University Center for the Utilization, Protection, and Management of Water Resources. 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