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#Ir ~--v ~-~l ~AAjj~ ~ /tlonh AmnicQPlJourna! of Fisheries Management 8:112-116, 1988 -e Copyriaht by Ihc American Fisheries Society 1988 Effects of Direct Current EJectrofishing on the Mottled Sculpin JEFFREY C. BARRETT School of Forest Resources and Institute of Ecology University of Georgia, Athens, Georgia 30602, USA GARY D. GROSSMAN \ \ School of Forest Resources University of Georgia Abstract. - We examined the effects of electrofishing on the survival of mottled sculpin COIlUS bairdi in two experiments. Three tanks each were filled with mottled sculpin collected by electro- fishing (treatment) and by kick-seining (control). We maintained these tanks for at least 30 d and recorded all deaths, Patterns of survival were not significantly different among tanks in either of the experiments, In addition, there were no significant differences between pooled data sets (all control tanks versus all treatment tanks) within each experiment. Failure to demonstrate a treatment effect in either experiment suggests that electrofishing does not adversely affect the short-term survival of mottled sculpin. Although sample sizes were insufficient for statistical analysis, a similar resuh was obtained for several other species of stream fishes, To test the effects of multiple electrofishing exposures, we conducted another experiment in four artificial stream sections, Treat- ment mottled sculpin were shocked, and both treatment and control fish were handled, weekly, for 5 weeks, Although overall survival in all stream sections was lower than that seen in the first two experiments, there were no significant differences in survival among sections or between treatments in this experiment. These data suggest that handling stress was a greater determinant of mortality rates than was eJectrofishing, :~. .-' :)' :3' 'I> :J :> ') 'f ~. f . I Electrofishing, a commonly used sampling tech- nique, may cause mortality or physical injury to fishes (Hauck 1949; Horak and Klein 1967; La- marque 1967; Spencer 1967; Schreck et al. 1976; Whaley et al. 1978). For example, electrofishing has caused broken and dislocated vertebrae and ruptured blood vessels in rainbow trout Salmo ", gairdneri (Hauck 1949; Horak and Klein 1967), brook trout Salvelinus fontinalis (Hudy 1985), bluegill Lepomis macrochirus, largemouth bass MicroptRrus salmoides, and channel catfish Ictalu- rus punctatus (Spencer 1967). In addition, a va- riety of sublethal effects (e,g., changes in blood physiology) have been noted in fishes after elec- troshocking(Schreck et al. 1976; Bouck et al. 1978; Burns and Lantz 1978; Gatz et al. 1986). For many types of studies, it is important to assess the effects of electrofishing on fish popula- tions. Researchers making repeated censuses (e.g., mark-recapture studies or long-term population d)'Damics studies) must avoid techniques that re- sult in fish mortality to reduce the risk of biasing their results (Pratt 1954), In addition, electrofish- ing effects should be known before this technique is used on endangered or threatened fish popula- tions. Most prior studies on the effects of electro fishing \x1 YJ ,-..J \ ") ...~~" 1 J\ "1\ \l Jj A... "",t:>, '~ \.. .~ ,(\ :: \i \ have not dealt with nongame species, In addition, the effects of multiple exposures to electricity have not been well documented. We examined the acute effects of both single and multiple exposures of non pulsed direct current on the mottled sculpin Cottus bairdi, Methods Single-exposure experiments. - We collected two groups of mottled sculpin from Dryman Fork, at the Coweeta Hydrologic Laboratory, Otto, North Carolina, in late February and early March 1985. Dryman Fork is a fourth-order stream oflow con- ductivity (annual range, 10-15 p.S) and low aver- age temperature (annual range, 2-190C; mean, SOC). Temperature at the time of collection was 5-80C. Treatment fish were electroshocked with a Smith- Root. model Xl-A, direct current electrofisher set to deJiver 600 V of nonpulsed current (200 W continuous output). We used a minnow seine 1- 2 m beloW the electro fisher to collect electro- shocked fish. Although this technique may have resulted in the capture of fish with unequal elec- trical exposures (e.g., heavily stunned fish versus mildly affected fish, etc.), it accurately represents the method of collection used in many studies (Reynolds 1983). 112 67/1{ EFFECTS OF ELECTROFlSHING ON SCULPiN 113 We drove control fishes into the seine by kicking the substrate (i.e., kick-seining). Kick-seined fish were examined visually to insure that they had not been injured during capture. We weighed (:to.5 g) and measured (standard length [SL], :t I mm) all fishes before randomly placing them into one of six 650-L fiberglass tanks. Three tanks contained control fish, and three tanks contained treatment fish, Each tank was provided with a continuous supply of stream water (approximately 12 L/min), which maintained water temperatures between 5 and 10oC. In each tank we placed 30 mottled scul- pin and 20 additional individuals in some com- bination of seven other species: Tennessee shiner Notropis leuciodus, warpaint shiner N. coccogenis, longnose dace Rhinichthys cataractae. largescale stoneroller Campostoma oligolepis, rosyside dace Clinostomusfunduloides, northern hog sucker Hy- pentelium nigricans, and creek chub Semotilus atromaculatus, Low capture success ,prevented stocking identical numbers of these species in each tank; however, overall species combinations gen- erally were equal in numbers offish between treat- ments, Because of the low abundances of these seven species, we will not discuss their results in detail. The mottled sculpin collected ranged from 32 to 87"mm SL (mean :t SD, 55.7 :t 9.7 mm) and from I to 15 gin weight (4. 14 :t 2,85 g). These six tanks will be referred to as experiment I. In late June and early July 1985, we collected two more groups of mottled sculpin from Dryman Fork using electrofishing (treatment fish) and kick- seining (control fish) for use in experiment II. Water temperature at the time of collection, and in the tanks during the course of this experiment, varied between 14 and 160C. These fish were marked with subcutaneous injections of acrylic paint and intro- duced into the same six tanks used for experiment I. Subcutaneous marking has been shown to have no statistically detectable effect on the survival of mottled sculpin (Hill and Grossman 1987). At this time, one of the experimental and two of the con- \trol tanks still contained several experiment-I fish, lwhich were being kept for long-term analysis. Con- kequently, to keep the total density offish in each tank constant, we had to introduce unequal num- bers of mottled sculpin into each tank for exper- iment II. The total number offish introduced var- ied from 11 to 33 individuals (mean, 19). These sculpin ranged from 36 to 89 mm SL (mean :t SD, 56.5 :t 10.4 mm) and ftom I to 16 g in weight (4.27 :t 2,69 g), Experiment-I and experiment-II fish could be differentiated by the presence of acrylic marks. We fed experiment-I fish a diet of brine shrimp, '$ chopped earthworms, and a commercial flake food ~ 5-6 times a week. This diet was changed to a ho- :::r mogenate of beef liver, brine shrimp, and com- \.. ~ mercial flake food, mixed with cod liver oil, gel- =F atin, agar and vitamins C, E, and A for experiment "l- II. In addition, during experiment II, we also added ~ malachite green (0. I mgIL) and formalin (25 mgIL) , to the tanks for 1-2 h once or twice weekly as a d prophylaxis. Vl For both experiments, we cleaned and inspected ~ the tanks one or two times per week, removed any 1.. dead fishes, and recorded their length and condi- 5 tion. If death occurred between tank inspections, the date of mortality was taken to be the midpoint _~ between the date the specimen was found and the ~ previous inspection date, Although some fish from ~ each experiment lived 90 d or more, problems oQ with disease outbreaks after 30+ d in captivity made the detection of electrofishing effects prob- lematical. Consequently, we considered only the first 30 d of each experiment for thL;analysis, For each experiment, we tested whether the sur- vival times of fish in the six tanks were signifi- cantly different using a Kruskal-Wallis test (P = 0.05 in this and subsequent tests). If the Kruskal- Wallis test was significant, multiple comparisons between tanks were made. Treatment effects, if any, could be inferred from the pattern of signif- icant between-tank differences. We also tested for treatment effects by pooling the data for each treat- ment (i,e" all control tanks vesus all experimental tanks) and testing for significant differences using a Mann-Whitney test. This latter test was con- ducted to reduce the effects ofintertank variability within a treatment. Henson Creek experiment, - To test the short- term effects of multiple exposures of electricity on mottled sculpin, we conducted a third experiment. We divided a concrete diversion channel on Hen- son Creek (Coweeta Hydrologic Laboratory) into four sections (2.4 x 0,6 m each) and then diverted the stream through these sections, Cobbles from the creek were added to create a natural substrate. Natural colonization of the substrate by macroin- vertebrates occurred during a 4-week period prior to the experiment. These invertebrates were the only food available to the fish except for a sup- plemental feeding of mealworms provided in the third week of the experiment. On September 9, 1985, we again collected treatment mottled scul- pin by electrofishing and control fish by kick-sein- ing. Water temperatures at the time of collection and during all subsequent collections ranged from