9491

• UCREFRP Catalog Number: 9491
• Author: Snyder, D. E.
• Title: Electrofishing and Its Harmful Effects on Fish.
• USFW Year: 2003.
• USFW - Doc Type: Denver.
• Copyright Material: NO

Contents (concluded)

Figures (concluded)

Page

8. Changes in current density and power density relative to voltage gradient in water with a conductivity

of500 JlS/cm ................................................................................................................................................... 15

9. Hypothetical two-dimensional diagrams of heterogeneous electric fields around and between

electrodes....................................................................................................................................................... 17

10. Distortion of homogenous electric fields around fish in water that is less conductive (top) and more

conductive (bottom) than the fish .................................................................................................................. 19

11. Major intensity-dependent electrofishing response zones ............................................................................ 24

12. Power-density-transfer curve......................................................................................................................... 25

13. Power-density-transfer curves fitted to peak-power-density threshold data for twitch, taxis (attraction),
and narcosis (stun) in 6- to 9-cm-TL goldfish (Carassius auratus) subjected to homogeneous fields

of DC ..... ...................... ........................................... ........................................................................................ 25

14. Peak-voltage-gradient-threshold curves for narcosis (stun) of6- to 9-cm-TL goldfish (Carassius
auratus) in homogeneous fields of DC; 50-Hz, square-wave PDC with duty cycles of50%, 25%, and

10%; and 60-Hz sinusoidal AC ....................................................................................................................... '29

15. Peak-power-density-threshold curves for narcosis (stun) of 6- to 9-cm- TL goldfish (Carassius auratus)
in homogeneous fields of DC; 50-Hz, square-wave PDC with duty cycles of50%, 25%, and 10%; and

60-Hz sinusoidal AC ......................................................... ..... ......................................................................... 30

16. Dorsal- (top) and lateral-view (bottom) X-rays of a rainbow trout (Oncorhynchus mykiss) revealing
spinal misalignment and fractured vertebrae caused by electrofishing ......................................................... 48

17. Necropsy fillets of rainbow trout (Oncorhynchus mykiss) revealing hemorrhages and associated tissue
and vertebral damage caused by electrofishing, top showing multiple injuries ............................................. 49

18. Fractured vertebrae from a rainbow trout (Oncorhynchus mykiss) caused by electrofishing........................ 50

19. X-rays of a natural spinal anomaly (A), an old spinal injury (B), and a recent electrofishing-caused spinal
injury (C) in rainbow trout (Oncorhynchus mykiss) ....................................................................................... 54

Appendices

A. Scientific names and families of fishes referenced by common name in this report ...................................... 127
B. Compendium of reported electro fishing mortalities and injuries by fish species and electrical current .......129

VII