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Research on Effects of Electrofishing USFWS proposal: Effect of Electroshocking on Native Southeastern Fishes with Emphasis on Species Protected under.

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Presentation on theme: "Research on Effects of Electrofishing USFWS proposal: Effect of Electroshocking on Native Southeastern Fishes with Emphasis on Species Protected under."— Presentation transcript:

1 Research on Effects of Electrofishing USFWS proposal: Effect of Electroshocking on Native Southeastern Fishes with Emphasis on Species Protected under the Endangered Species Act USFWS proposal: Effect of Electroshocking on Native Southeastern Fishes with Emphasis on Species Protected under the Endangered Species Act J.R. Shute, P. Rakes (Conservation Fisheries Inc.) J.R. Shute, P. Rakes (Conservation Fisheries Inc.) Support for graduate research assistant (M.S.) to begin fall 2006 (Dept FWF, UTK) Support for graduate research assistant (M.S.) to begin fall 2006 (Dept FWF, UTK) Project objectives Project objectives Additional funding Additional funding Ted Henry, Adjunct Assistant Professor Dept of Forestry, Wildlife, and Fisheries University of Tennessee, Knoxville, TN

2 Overall Objectives for Electrofishing Injury Research Consider effect of different electric field types (e.g., DC PDC) and investigate: Consider effect of different electric field types (e.g., DC PDC) and investigate: Survival of embryos Survival of embryos Survival of vulnerable older life stages Survival of vulnerable older life stages Sub-lethal injury to tissues Sub-lethal injury to tissues Consider T&E species or surrogates Consider T&E species or surrogates Darters, madtoms, and shiners Darters, madtoms, and shiners

3 Electroshocking and Fish Early Life Stages - Early life stages not targets of electrofishing - Exposed during sampling for target fish - Electrofishing during spawning season - Effects of electrofishing on early life stages?

4 Previous Electrofishing Injury Research Projected funded by the USFWS through the Fisheries Management Section of AFS Projected funded by the USFWS through the Fisheries Management Section of AFS Examined effects of electrofishing in early life stages of warmwater fish (focused mostly on sportfish) Examined effects of electrofishing in early life stages of warmwater fish (focused mostly on sportfish) Laboratory based research with field validation Laboratory based research with field validation Results indicate that investigations on effects on T&E species are necessary Results indicate that investigations on effects on T&E species are necessary

5 30 cm Modified electrofishing pulse box Oscilloscope Aluminum plate electrodes homogeneous electric field Model of exposure chamber Research Methods

6 Channel catfish embryos in exposure chambers Chambers had flow-through water exchange

7 Survival of Largemouth Bass Embryos after Exposure to 8 V/cm Control (survival 83%) Hatching 48 h Similar results for bluegill embryos

8 25 mm channel catfish

9 Age-related Mortality of Largemouth Bass 60-Hz PDC cm

10 Electroshock-Induced Mortality of Newly Transformed Juvenile Fish 60-Hz PDC for 20 s Channel catfish Nile tilapia Rainbow trout Blackbanded darter* Largemouth bass *adult

11 Grossly Visible Injuries Species Number shocked Number injured control fish 1380 channel catfish (4 dead) rainbow trout striped bass 681 largemouth bass 3241 bluegill3113 Nile tilapia 1474

12 channel catfish anterior tail sagittal section control electroshocked 20 s, 4 V/cm, 60-Hz PDC spinal cord dorsal aorta vertebra notochord compressed vertebra

13 bluegill anterior tail sagittal section electroshocked 5 s, 8 V/cm, 60-Hz PDC Fractured vertebra (arrow) and hemorrhage (H) H live fish had no indications of injury

14 Rainbow trout anterior tail sagittal section electroshocked 20 s, 4 V/cm, 30-Hz PDC Notochord hernia protruding between vertebrae spinal cord notochord hernia vertebrae live fish had paralysis of the tail and posterior trunk

15 Nile tilapia anterior tail sagittal section electroshocked 20 s, 16 V/cm, 60-Hz PDC Necrotic muscle (arrows) live fish had uncoordinated swimming necrotic muscle also found in control fish: 1 largemouth bass and 1 bluegill

16 Histopathology of Clinically Normal Fish 1 Hour After Electroshock Lesions channel catfish 4 V/cm bluegill largemouth bass 2 V/cm Fish examined Vertebral fracture Vertebral fracture200 Vert. compression Vert. compression600 Notochord hernia Notochord hernia400 Hemorrhage Hemorrhage202 Necrotic muscle Necrotic muscle9104 Total fish injured 60%63%18%

17 Lesions in clinically normal bluegill after exposure to 8 V/cm for 5 s Fish examined 12 Vertebral fracture Vertebral fracture2 Vertebral comp. Vertebral comp.2 Notochord hernia Notochord hernia1 Hemorrhage Hemorrhage3 Necrotic muscle Necrotic muscle8 Total fish injured 67%

18 Conclusions Embryos Embryos More susceptible to DC than PDC More susceptible to DC than PDC Most susceptible stage is near epiboly Most susceptible stage is near epiboly Exposure can induce premature hatching Exposure can induce premature hatching Even short exposure can be lethal Even short exposure can be lethal Posthatching developmental stages Posthatching developmental stages Newly transformed juveniles most susceptible to lethal effects Newly transformed juveniles most susceptible to lethal effects Susceptibility to electroshock-induced mortality varies among species Susceptibility to electroshock-induced mortality varies among species

19 Conclusions Newly transformed juvenile fish can be injured by electric fields Newly transformed juvenile fish can be injured by electric fields Injuries are seldom detectable by gross, external examination Injuries are seldom detectable by gross, external examination Microscopic injuries can be common Microscopic injuries can be common Injuries can be severe, including vertebral fracture Injuries can be severe, including vertebral fracture Short exposure durations (5 s) can injure a high percentage of fish Short exposure durations (5 s) can injure a high percentage of fish

20 Implications for Threatened and Endangered Species Exposure of embryos: Exposure of embryos: Nest building species, all embryos exposed during a single electrofishing event Nest building species, all embryos exposed during a single electrofishing event Spawning aggregations may be particularly vulnerable Spawning aggregations may be particularly vulnerable Exposure of older life stages: Exposure of older life stages: Newly transformed juveniles may be most vulnerable and have highest mortality Newly transformed juveniles may be most vulnerable and have highest mortality Tissue injuries may occur in most of the fish that are exposed Tissue injuries may occur in most of the fish that are exposed

21 Acknowledgments USFWS/AFS Fisheries Management Section USFWS/AFS Fisheries Management Section John Grizzle, Auburn University John Grizzle, Auburn University M.S. research assistant position announcement Electrofishing publication list: pdf files available


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