Electroshock Effects on Fish

1. Electroshock Effects on Fish

2. Session Purposes • To investigate typical reactions of fish in electric fields generated by various waveforms • To describe fish trauma issues at the individual, sample, and population levels • To discuss methods for minimizing the potential of fish trauma

3. Session Objectives • List and order typical reactions of fish in AC, DC, and pulsed DC electric fields • Describe attributes of fish trauma and factors leading to trauma • Discuss methods for minimizing the potential of fish trauma, including the use of an injury risk model • Describe injury assessment methods on the sample, reach, and population levels

4. A. Two Categories of Electroshock Effects • Behavior (or reactive movements) • Use of certain responses for capture or control • Trauma (stress or injury) • Stress is usually physiological (no mechanical injury) • recovery short-term • Injury is mechanical • recovery long-term (although maybe with reduced growth or fecundity)

5. B. Fish Behavior in Electric Fields

6. For Practical Use in Field • Escape (upright avoidance swimming) • Inhibited swimming (unbalanced swimming) • Immobilization (no swimming motions) Inhibited swimming includes taxis, pseudo-taxis, oscillotaxis Immobilization includes narcosis & tetany

7. Common Terms Inhibited Swimming • Taxis or electrotaxis: electrically-induced movement, usually toward the anode • False Taxis or pseudo-forced swimming: as electrotaxis except the fish is unconscious and belly-up • Oscillotaxis: electrically-induced movement without orientation

8. Common Terms (continued) Immobilization • Tetany: a state of electrically-induced immobility with rigid muscles • Narcosis: a state of electrically-induced immobility with slack muscles

9. Videos of Behaviors • Inhibited swimming (compromised swimming) • Inhibited swimming (taxis) • Immobilization (narcosis) • Reactions and their neurological causes (Barritz Lab)

10. Behavior in Electric Fields From an illustration in Sternin et al. (1972)

11. Fish Response to AC Escape (or Fright) response Inhibited swimming Transverse oscillotaxis Tetany

12. F Fish Response to DC “Immobilization”: tetany or narcosis

13. Fish Response to DC “Anodic curvature” Taxis Immobilization

14. Fish Response to Pulsed DC • May or may not cause taxis • Taxis response observed (for brown trout, Salmo trutta) • Taxis response not observed (for goldfish, Carassius auratus) • Lamarque (1990) concluded from lab experiments that PDC has poorer anodic taxis as compared to DC • Complicated because of the many different types of PDC waveforms • May be somewhat intermediate between AC & DC responses (can have taxis, narcosis, and tetany responses)

15. Quiz Question(Tetany or Narcosis?)

16. Narcosis • Gentle curvature of body • Absence of “flared gills” (a characteristic of tetany)

17. C. Fish Trauma: Stress • Physiological stress incorporates a wide range of chemical and physical responses that occur as a direct effect of a stressor causing disruption in the homeostasis of the body. • Bottom-line: What are the implications for short-term sampling and longer-term fish health and survival? • In other words, does changed physiology translate to changed behavior, and if so, for how long? Also, under what conditions does stress lead to higher mortality?

18. TraumaGeneralized Stress Response Model

19. Fish Physiological Indicators of Stress from Electroshock • Blood chemistry • Common parameters include: cortisol, lactate, glucose (others include hematocrit, oxygen saturation, electrolytes [osmolality], enzymes [creatine kinase], minerals [calcium], proteins [albumin] • Physical • Parameters include: gilling rate (ventilation), cardiac output

20. Blood Chemistry Responses • Hormonal • Immediate adrenergic release of catecholamines (e.g., epinephrine and norepinephrine) • Followed by corticosteroid release (especially cortisol) • Metabolic • Increased lactate (from muscle exertion) • Increased glucose • Development of metabolic and respiratory acidosis which can, in turn, initiate respiratory compensation (increased gilling and oxygen saturation)

21. Lab Example Using DC (1), PDC (2), AC (3) O2 % Time (minutes)

22. Plasma Cortisol in Fall Chinook Salmon *1.5 sec., 500 V DC Sample at time = 0 taken 4 sec post-shock “a” = shocked mean different from control mean at that time “b” =shocked mean different from mean of all controls “c” =shocked mean different from shocked mean at time 0

23. Blood Chemistry Recovery Times and Correlations • Chemical parameters as cortisol, lactate, glucose, and osmolarity typically are resolved within six hours or begin to diminish during that period post-shock • If the stressor (shock duration) is very short, the cortisol response may be short and have quick recovery • Glucose and lactate are metabolic responses and may persist for a longer period after shock as compared to cortisol

24. Blood Chemistry Recovery Times and Correlations • Multiple shocks have resulted in greater changes in cortisol and lactate • However, some research has been unable to link blood chemistry changes with intensity of electric shock, duration, presence of hemorrhagic trauma to musculature, or short-term mortality

25. Physical Responses • Muscle contraction (tetany) or increased exercise (as beginning of flight response) • Reduced ventilation • Lowered followed by amplified cardiac output

26. Rainbow Trout EKG Waveform applied:PDC, 100 V, 30 Hz, 2 ms pulse width for 32 sec Shaded area: electrical power on Schreer et al. (2004)

27. Rainbow Trout EKG Waveform used: 100 V, 80 – 8 Hz, 2 ms, for 8 sec Found that longer shock durations increased the duration of cardiac arrest & recovery Cardiac output Heart rate Stroke volume Vertical shaded bars: electrical power on

28. Metabolic Implications • Lactic acid may accumulate due to the increased muscular contraction and reduction of ventilation • Metabolic acidosis and respiratory acidosis can result • Recovery from acidosis takes time and energetic resources • Six hours may see recovery or the start of recovery • For population assessment, the key is behavior; is the individual fish exhibiting normal behavior

29. Time Interval between Passes • Behavioral recovery may lag blood chemistry dynamics; Mesa & Schreck (1989) determined that a waiting period of 6 hours may not be adequate; rather 24 hours were needed for recovery in Westslope cutthroat trout and recommended a day between the first and second sampling events in mark-recapture work • There may be a balancing act between recovery and movement or predation out of sample sites • Block nets probably necessary (Peterson et al. 2005) • Mesa & Schreck (1989) did not see abnormal behavior of un-captured fish remaining in the sampling site during depletion sampling

30. Predicted Probability of Mortality for Cape Fear Shiners Exposed to 60 Hz PDC No injures (vertebrae fractures or hemorrhages) were detected Holliman et al. (2003)

31. Stress-related Effects of EFWaveform Shape Recovery time of common carp 50 Hz PDC; Vertical line = 1 standard error D.J. Bird & I.G. Cowx. 1993. Fisheries Research 18:363-376.

32. Stress-related Effects of EF • Smaller fish usually do not have a high incidence of injuries (< 10%) but are susceptible to stress • Stress-related physiological changes are typically short-term (3 – 6 hours) • Related behavioral effects (e.g., reduced feeding or predator avoidance, lethargy) may last 24 hours • Holliman et al. (2003) concluded that if small cyprinids appear and behave normally 1 hr. post-electroshock, then biologists can consider stress minimal and mortality near zero • Mortality can occur with smaller fish due to stress and is influenced by… • Field intensity ( higher voltage gradient, pulse frequency) • Durationof exposure (longer) • Length of fish (larger) • Waveformshape (1/4 sine-wave PDC highest recovery time) • Waveformtype (rule-of-thumb AC>PDC>DC, but 60 Hz PDC caused less stress-related mortality in Cape Fear shiners than DC [Holliman et al. 2003] and AC and 60 Hz PDC resulted in similar stress-related mortality in spotfin chubs inhabiting low conductivity water [Holliman and Reynolds 2003])

33. Stress-related Mortality • In several warmwater game and non-game fishes, lower frequency and duty cycle tended to result in higher mortality

34. Stress-related Mortality Percentages • Warmwater fishes: 2-3 day mortality 0.6%, all with fishes ≤ 53 mm (Miranda 2005) • RBT (> 400 mm ): 4 day mortality 14% (Holmes et al. 1990) • Bluegill, channel catfish, largemouth bass: 10% mortality (Dolan and Miranda 2004) • Atlanic salmon (<80mm): no significant effects on mortality when shocked 4 times at 2 month intervals (Sigourney et al. 2005) • Largemouth bass, smallmouth bass, bluegill, pumkinseed: mortality ≤ 5.3% (Bardygula-Nonn 1995) • Cape Fear shiner: < 10% mortality with 60 Hz PDC

35. To reduce stress in the field: -use the lowest effective level of power -net the fish away from the electrodes -net the fish as quickly as possible -do not re-introduce captured fish back into the field

36. D. Trauma- Injury (external) “Brands” (chevron-shaped bruises) Arctic grayling *Can lead to secondary fungal infections *An indicator of probable internal injuries

37. Trauma- Injury (external) ~98% injury rate ~50% injury rate If brands present, higher likelihood of more severe, internal injuries Injury severity increases from class 1 to class 3

38. Trauma- Injury (internal) Internal Hemorrhage Classification System

39. Internal Hemorrhage Classification Can be frozen before filleting Blood from filleting process easily wipes off; hemorrhages do not

40. Internal Hemorrhage Classification

41. E. Trauma- Injury (internal) Spinal Damage Classification System

42. Spinal Injury Classification

43. Spinal Injury Classification

44. Spinal Injury Classification

45. Spinal Injury Classification Lateral view

46. Spinal Injury Classification Dorsal view

47. Spinal Injury Normal Brown trout vertebrae Fractured from EF

48. Spinal Injury Brown trout vertebrae Old, calcified injury Recent fracture from EF

49. Location of Internal Injuries% of Length Posterior from Snout Dorsal Anal

50. Location of Internal Injuries Brown trout Most spinal injury in dorsal fin region where dorso-lateral muscle mass is the thickest