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I I I I I I I I I I I I I I I I I I I CONTENTS LIST OF TABLES ................... IV LIST OF FIGURES . . . . . . . . . . . . . . . . . . .. IV LIST OF APPENDICES ................ IV ACKNOWLEDGEMENTS .............. V SUMMARy......................... .vi INTRODUCTION . . . . . . . . . . . . . . . . . . . .. 1 ~THODS ......................... 3 REVIEW AND COMMENTARY ......... 3 ELECTRIC FIELDS IN WATER. . . . . .. 8 Water Conductivity .............. 8 Field Strength .................. 9 Heterogeneous and Homogeneous Fields ..................... 13 Bounding Substrates and Interspersed Objects . . . . . . . . . . . . . . . . . . .. 15 Size, Shape, and Position of the Electrodes . . . . . . . . . . . . . . . . .. 15 Electrofishing Currents and Wavefonns 17 RESPONSES TO ELECTRIC FIELDS. .. 19 Major Intensity-Dependent Responses . 21 Response Thresholds .......... 23 Zone of Reactive Detection ..... 25 Zones of Undirected or Inhibited Swimming and Taxis ....... 25 Zones of Narcosis and Tetany . . .. 28 Comparison of Currents for Electrofishing ............... 29 ADVERSE IMPACTS. . . . . . . . . . . . . .. 31 Effects Other Than Spinal and Related Injuries . . . . . . . . . . . . . . . . . . .. 31 Spinal and Related Injuries . . . . . . . .. 51 Nature of the Injuries. . . . . . . . .. 51 Detection and Evaluation of the Injuries ................. 55 Relationship Between Injury and Mortality . . . . . . . . . . . . . . .. 57 Factors Affecting Injuries, Mortality ,and Other Adverse Effects .................... 59 Type of Current . . . . . . . . . . . . .. 59 Field Intensity . . . . . . . . . . . . . .. 63 Length of Exposure ........... 65 Pulse Shape, Wavefonn ........ 65 Pulse Frequency, Pulse Trains . . .. 66 Pulse Duration . . . . . . . . . . . . . .. 68 Voltage Spikes .............. 68 Species . . . . . . . . . . . . . . . . . . .. 69 Size ...................... 70 Condition .................. 71 Long-Tenn Survival and Growth .... 71 Effects on Reproduction, Gametes, and Offspring .................. 74 Effects on Early-Life Stages . . . . . . .. 74 SUMMARY OF SURVEY RESPONSES . 76 Experience .................... 76 Observations of Adverse Effects on Fish ...................... 77 Respondent Recommendations for Minimizing Adverse Effects .. . .. 79 CONCLUSIONS . . . . . . . . . . . . . . . . . . . . .. 80 RESPONSE TO SPECIFIC QUESTIONS . 80 FUTURE RESEARCH .............. 88 RECOMMENDATIONS ................ 89 INTERIM POLICY TO MINIMIZE ELECTRO FISHING INJURY ...... 89 RESEARCH ON ELECTROFISHING INJURIES AND RESPONSES . . . . .. 93 LITERATURE AND PERSONAL COMMUNICATIONS CITED . . . . . . . .. 98 PUBLICATIONS, AGENCY REPORTS, MANUALS, ~ETING ABSTRACTS 98 UNPUBLISHED MANUSCRIPTS. .... 106 PERSONAL COMMUNICATIONS. . .. 106 jjj