Page 0065

Appendix 1

RSPCA welfare standards for farmed Atlantic salmon 58 September 2015

* indicates an amendment

10. Assessing the effectiveness of stunning

First, watch fish arriving at the stunning table from the fish pump. Time how long it is between a particular

fish arriving and it being stunned. Note down the time and then repeat for about ten fish. Work out the

average. As a guide, if the average 'arrival to stunning time' is more than five seconds then the operation

needs to be improved.

Reduce the flow of fish to the table by slowing the fish pump and/or reducing the crowd density. Then look

at the ergonomics of the killing table. Could fish delivery, presentation or handling be improved by

modifying the table with dividers or higher/lower edges or rubber mats, placing the stunners in a different

position or are more stunning machines needed? It is surprising how many killing tables are ergonomically

not well laid out. Try modifications to the table with temporary wood partitions etc. and evaluate the

effectiveness of these modifications before having the table modified by professionals.

Second, observe the stunning operation. Count how many stunning blows are needed to stun a particular

fish. Note down the number and then repeat for about ten fish. If fish require more than one stunning blow,

then the operation and/or set up of the stunner needs to be improved. Check that the operator is presenting

fish correctly, that sufficient air pressure is available and that the machines have been maintained and are

not obstructed in any way. Re-evaluate the stunning process. If fish require more than one stunning blow,

then the operation must be stopped and the manufacturers of the machine need to be contacted.

Note that the unconsciousness induced by percussive stunning should be immediate and permanent i.e.

the fish should not recover from the blow, even if it is not bled. Bleeding is not part of the killing operation

but is done for flesh quality reasons.

11. Determining whether fish are adequately stunned

Observe fish immediately after stunning. In a properly stunned fish a reflex shudder or tail flap will usually

occur for a few seconds after stunning. Do not be worried about this reflex movement if it lasts for up to four

seconds. But if movement lasts for much more than four seconds, it is not a reflex and stunning is not being

done effectively.

If there is no overt movement in fish after four seconds, pick the fish up and examine it. Look for signs of

rhythmic breathing and eye roll. These are the best signs to look for to determine if the fish is properly

stunned. This is because rhythmic breathing and eye roll are both signs of brain stem activity - if they are

absent it is safe to conclude that the fish is deeply unconscious.

 Rhythmic breathing appears as rhythmic movements of the operculum (gill cover) (and sometimes

the mouth). Note that occasionally fish that have been properly stunned will flare their gills a few

minutes after stunning. This is a reflex action and, provided it is not repeated more than a couple of

times, can be ignored.

 To observe eye roll, with the fish lying on its side, look at the movement of the eye when the fish is

rolled upright and then back again. In a stunned or dead fish the eye will remain flat and fixed in

the skull. In a conscious fish or one that has not been properly stunned (i.e. with brain function),

the eye will appear to move in the eye socket, trying to remain upright when the fish is rolled onto

its side.

If there is no sign of rhythmic breathing or eye roll then the fish is properly stunned. If rhythmic breathing or

eye roll can be observed, then the fish is not adequately stunned. Practice observing rhythmic breathing

and eye roll on a few fish before they are stunned so that you know what to look for.

Make sure that all people involved in stunning and bleeding fish know that if a fish is fighting or responding

to handling in any way it is not unconscious and must be stunned before anything else is done to it. If a fish

responds to handling or the cut of the knife when exsanguinated then it is definitely not stunned.

Index

  1. Page 0001
  2. Page 0002
  3. Page 0003
  4. Page 0004
  5. Page 0005
  6. Page 0006
  7. Page 0007
  8. Page 0008
  9. Page 0009
  10. Page 0010
  11. Page 0011
  12. Page 0012
  13. Page 0013
  14. Page 0014
  15. Page 0015
  16. Page 0016
  17. Page 0017
  18. Page 0018
  19. Page 0019
  20. Page 0020
  21. Page 0021
  22. Page 0022
  23. Page 0023
  24. Page 0024
  25. Page 0025
  26. Page 0026
  27. Page 0027
  28. Page 0028
  29. Page 0029
  30. Page 0030
  31. Page 0031
  32. Page 0032
  33. Page 0033
  34. Page 0034
  35. Page 0035
  36. Page 0036
  37. Page 0037
  38. Page 0038
  39. Page 0039
  40. Page 0040
  41. Page 0041
  42. Page 0042
  43. Page 0043
  44. Page 0044
  45. Page 0045
  46. Page 0046
  47. Page 0047
  48. Page 0048
  49. Page 0049
  50. Page 0050
  51. Page 0051
  52. Page 0052
  53. Page 0053
  54. Page 0054
  55. Page 0055
  56. Page 0056
  57. Page 0057
  58. Page 0058
  59. Page 0059
  60. Page 0060
  61. Page 0061
  62. Page 0062
  63. Page 0063
  64. Page 0064
  65. Page 0065
  66. Page 0066
  67. Page 0067
  68. Page 0068
  69. Page 0069
  70. Page 0070
  71. Page 0071
  72. Page 0072
  73. Page 0073
  74. Page 0074
  75. Page 0075
  76. Page 0076
  77. Page 0077
  78. Page 0078
  79. Page 0079
  80. Page 0080