9491 - Laserfiche WebLink

Home Browse Search

Contents Page Foreword ........ ......... ........ ......................................................................................... ............................ ......... ............... iii Preface .............................................................................................................................. ........................................... iv Abstract .............................................................................................................................. .......................................... 1 Introduction .............................................................................................................................. .................................... 1 Methods......... ......... ............................ ........ ............... .......................... ......................................................................... 3 Results - Historical Overview..................................................................................................................................... 4 Results - Electric Fields in Water ................................................................................................................................ 9 Water Conductivity.................................................................... ..................... ......... ........ ....... ....... ........................... 9 Electrofishing Currents and Waveforms .................................................................................................................. 10 Field Intensity......................................................... .......... ............................... ........................................................ 12 Heterogeneous and Homogeneous Fields ............................................................................................................... 16 Bounding or Surrounded Media and Substrates ..................................................................................................... 16 Electrodes - Position, Size, Shape, and Other Matters .......................................................................................... 18 Results - Responses ofFish to Electric Fields .......................................................................................................... 21 Biarritz and Bozeman Paradigms .............................................................................................................................. 21 Theory of Power Transfer from Water to Fish ......................................................................................................... 23 Maj or Intensity-Dependent Responses................................................................................................................... 28 Response Thresholds ......................................................................................................... ............................... 31 Zone of Reactive Detection................................................................................................................................ 37 Zones of Undirected or Inhibited Swimming and Taxis ...................................................................................... 37 Zones of Narcosis and Tetany ........................................................................................................................... 38 Comparison of Currents for Electrofishing Purposes ............................................................................................... 40 Results - Harmful Effects of Electro fishing on Fish .................................................................................................. 42 Effects Other than Spinal and Related Injuries ........................................................................................................ 43 Spinal and Related Injuries ...................................................................................................................................... 46 Nature of the Injuries.......................................................................................................................................... 47 Detection and Evaluation of the Injuries ............................................................................................................ 51 Relation Between Injury and Mortality .............................................................................................................. 55 Factors Affecting E1ectrofishing Injury and Mortality ...........................................................,................................. 55 Type of Current.................. ..................................................................... ... .............. ........ ................ .......... ........ 56 Mortality... ....................... ....................................... ........................................................................ ............. 56 Injury .............................................................................................................................. ............................. 57 Field Intensity .................................................................................................................................................... 62 Mortality .............................................................................................................................. ........................ 62 Injury .............................................................................................................................. ............................. 64 Duration of Exposure ....................................... ................................................................................................... 68 Waveform, Pulse Shape ...................................................................................................................................... (f) Pulse Frequency.... ......... .................................................................................................................................... 70 Pulse Trains. ....... ..................................... .......................... ................................................................................. 72 Pulse Duration, Duty Cycle ................................................................................................................................ 74 Voltage Spikes ................. .................. ............................................................... .................................................. 75 Species....................................................................................................................... ........................................ 75 Mortality .............................................................................................................................. ........................ 75 Injury .............................................................................................................................. ............................. 76 Size .............................................................................................................................. ....................................... 79 Condition .............................................................................................................................. ............................. 80 Repeated Exposures ...........................................................................................................................,.. ............. 81 Sununary ..... ............... ................. ....... ..... ........................................ ............... ....... ...... ......... ....... .... ..... ... ....... ..... 82 Effects on Long-Term Survival ................................................................................................................................ 84 Effects on Growth and Condition ............................................................................................................................ 86 v